On September 06, 2020, it was 122F in my yard in Ojai, California. A new all time high never before recorded in Ojai, Ca.
Here in California we had an extreme heat event on September 6, 2020. In my yard temperatures peaked at 120 degrees F. This also happened back in 2018 earlier in the summer where we reached a similar peak temperature. It is not supposed to get to be 120 degrees F. in Ojai. This year new high temperature records were set all over southern California for the month of September. Following these heat extremes, wildfires have spread from border to border (Canada to Mexico) in western states. As we suffer through heat and flames here in Western US states, we are also now told that this is a la Nina year so Southern California will continue with drought conditions into 2021. Extremes in climate bring hot dry weather to the Western United States and hurricanes and drenching rains to the eastern United States. Plants in landscapes may or may not be adapted to these extremes.
Damage from September 6, 2020 heat day showing damage to foliage on the tree on the right; a native Coast Live Oak (Quercus agrifolia), but not on the non-native Peruvian Pepper (Schinus mole).
My poster child heat monitor is the coast live oak, Quercus agrifolia. When temperatures exceed triple digits >110F, foliage on this native oak turn brown and burn on the south exposed canopies. They are not adapted to these record temperatures. This can be evidenced by looking at the damage throughout many California communities. Coincidentally other non-native plants are better adapted to high temperatures. The California pepper or Peruvian Pepper (Schinus mole) does fine in 120F weather with no irrigation. Eucalyptus of several species also have tolerated these increased temperatures. Trees that are drought stressed from lack of irrigation after a long dry summer will sunburn more severely than the same plants under consistent irrigation. If you see this kind of damage, its best to leave it alone until the plant responds by growing new shoots.
Damage to the tender new growth and leaves of Cherimoya. Sunburn symptoms usually show in the middle of leaves.
While study of “climate ready” trees is giving us tree selection options for hotter climates, the research is still new and we have many other species to consider beyond what has been recently reported. Of the species I have in Ventura County few of our study trees showed any damage from the extreme heat, and only the very youngest leaves were damaged on western hackberry and Catalina Cherry. Pistache, Island Oak, Palo Blanco, Tecate cypress, Arizona madrone, and Ghost Gum were not affected by triple digit weather this September. Other ornamental species that were damaged all over Southern California include the following: Avocado, Camphor, Privet, Magnolia, Coast Live Oak, Sycamore (especially the native Platanus racemosa), loquat and ornamental plum.
It our recent heat damage surveys I have observed that Coast Live Oak and Western Sycamore, two native trees that enjoy widespread tree ordinance protections were consistently damaged by our hot day early this month. If we continue to have extreme hot days, poorly adapted native trees will be injured more frequently, and possibly become more susceptible to damaging insects or native pathogens. This tends to restrict the range of natives to areas they are still adapted to growing in or grow into a new region where they are more successful. A time may come when a native tree is not the best choice for your area.
McPherson E.G., Berry, A.M., van Doorn, N.S., Downer, J, Hartin, J., Haver, D., and E. Teach. 2020. Climate-Ready Tree Study: Update for Southern California Communities. Western Arborist 45:12-18.
As summer winds down and the summer crops and flowers start
to slow down many gardeners start thinking about saving seeds. Who doesn’t love
saving seeds from that favorite tomato or beautiful coneflower? Not only do you have some for next year, but
you can also share with your friends! There are definitely some things to
consider and some myths out there when it comes to seed saving, so let’s talk
about how to do it right.
You’ll get the most consistent results from open pollinated or heirloom varieties that are self-pollinating. These plants have genetics stable enough that the seeds you save will come out looking and acting like a close approximation to the plants from the previous season (with some variation based on your selection of the “best” plants you save seeds from. Self-pollinating species are: tomatoes, peppers, eggplant, beans, peas, peanuts (note, peppers and eggplants have more open floral structures that can be cross pollinated). Most tree fruits like apples and pears are cross pollinated and they are notorious for not “breeding true” – even if you hand pollinate to ensure that the mother and father are both the same cultivar you’re likely to get surprises. Stone fruits (peaches, plums, etc) are less variable but still not true-breeding. Bee pollinated plants are also notoriously hard to save seed from, since they can cross pollinate with different varieties and cultivars from miles away. It is especially interesting for plants that look totally different but are the same species (like pumpkin and zucchini).
A puccini or a zumpkin? Either way, it tasted nasty.
Myth: You can’t save seeds from those new modified hybrid plants. They’ve been made to be sterile
First off, hybrids aren’t genetically engineered and there are no GE plants available to home gardeners (most home garden crops don’t even have GE versions). Hybrid plants do in fact usually produce viable seeds. However, you won’t get the consistent results you will with open pollinated/hybrid varieties. Hybrids are the F1 generation of a specific cross between a mother and father plant. The offspring from that F1 generation (the plants from the seeds you save) is called the F2 generation will be a mix of traits – some will look like the F1 generation, some will look like the mother, some the father, and some the milkman. So you’ll be in for a mixed bag of surprises. According to our former GP colleague Joseph Tychonievich’s book “Plant Breeding for Home Gardeners” you can even develop a stable open pollinated variety from hybrids by saving seeds over a few seasons, selecting seeds from the plants that most resemble the cultivar you’re trying to save.
You’ll want to make sure that the fruit/flower head that
you’re saving seed from is mature. This
can be tricky for some vegetables, because we eat them in their immature
states. Peppers need to change from
green to whatever their color is (red, yellow, orange, purple, etc), cucumbers and zucchini (and other squash)
need to turn into those massive, bloated fruits that often change to yellow or
orange. Beans often need to change to
yellow or tan (and may have stripes).
For flowers, the seed heads or fruiting structures often need to turn
brown and dry or start to open.
If the weather cooperates, you’ll want to collect seeds from
dry fruits/structured (beans, some flowers, etc) before significant rainfall so
that seeds don’t become wet and potentially mold or break dormancy. Collect seeds and place in a warm, dry
location to let them continue drying out (if they’re small you want to put them
somewhere they won’t blow away). After
drying, store seeds in envelopes or containers and put them in a cool dry
place. I often tell people to store
seeds in the freezer – the cold temperature slows down respiration in the seeds
and can extend their lifespan (the fridge is too moist/humid). If you do that, drop your envelopes or
containers down into a sealable container or bag to help keep condensation
minimal when you pull them out of the freezer next year.
For home gardeners, it may not matter that you get plants
next year that exactly copy the ones you saved seeds from – the fun can be in
the surprise. Who knows, you may
discover a new variety – at least one that is exciting to you. It can be fun seeing the variation in your
new plants and finding something that you love.
Epilogue: A special case – tomatoes
Most of the vegetable crops we grow don’t need any special treatment to break their dormancy (you’ll have to research flowers on a case-by-case basis) – save the seed and plant it next year and it will pop up. Tomatoes are a bit of a special case. If you scrape the seeds out of the fruit you’ll notice they’re still covered with the “goo” from inside the tomato which is called interlocular fluid (interlocular = between seeds). The coating persists on the seed even if you wash them. It has long been held that this coating retains some of the hormones of the fruit (like abscisic acid) that inhibits germination (though not all experts agree). So many sources will tell you to go through some process to break down the coating left on the seed, most commonly by placing the seeds and associated goo in a container, adding a bit of water, and letting them ferment for a few days. You can dump them out and wash off all the gunk. Whether or not this is required to break dormancy is up for debate, but it does provide you with clean seeds that you can store easily. There is also some evidence to suggest that this fermentation process helps remove pathogens on the exterior of the seed (heat treatment can help remove interior pathogens as well).
Some people just scoop out the seeds and smear the goo on a
paper towel and try to scrape them off next year. Some people add the step of washing, but this
will still not remove all of the goo coating the seeds. This works if you’re
not trying to share (or sell seeds) since they will stick to the paper towel. My
guess is that the in the day or so that it takes for the goo to dry there is
enough fermentation or decomposition going on to break dormancy. If you don’t want the seeds stuck to a paper
towel, you can use wax paper or some other non-binding surface, but you’ll
still have dried goo on your seeds.
Wildfires are increasingly threatening urban areas. Photo from Wikimedia.
This topic may have no relevance to where you live – but it’s very much front and center here in western Washington this summer. Our naturally droughty summers have gotten longer, hotter, and drier thanks to climate change. Wildfires are ravaging all of the west coast, on both sides of the Cascade mountains. And one of the recommendations I see for fire-proofing your landscape is to remove all wood-based mulch. While this might seem logical, it’s not. And here’s why.
Bark mulch and wood chip mulch may look similar, but they function differently
Not all wood mulches are equal. Wood chip mulches, which readily absorb water, are different than bark mulches, which can be quite impervious to water based on the type of bark and how fresh it is. The waxy components of bark not only make it resistant to water movement, they also more likely to burn. Likewise, pine needles, cones, straw, and other coarse organic mulches absorb little water and easily ignite. They should be avoided in fire-prone areas.
Pine needles and pinecones are a natural mulch layer in pine forests – but they burn readily. Photo by Pxfuel.
Wood chips are one of the least flammable mulches, and if landscape plants are properly irrigated, the wood chip layer is going to be increasingly moist as you work your way down to the soil. This reduces flammability, while maintaining plant health. And healthy plants are more likely to survive fires than water-stressed plants – because they are full of water. (Oh, and those “flammability lists” of plants you might see? Dr. Jim Downer has already debunked that approach.)
Rubber mulches are the very worst choice you can make for a wildfire-resistant landscape. They burn readily and they burn hot.
The best way to reduce wildfire damage to your planted landscape is to keep it irrigated. Bare soil is a no-no in planted landscapes, regardless of what you might see recommended elsewhere. A well-hydrated landscape with green lawns and healthy trees and shrubs is not going to catch fire from a spark or ember. And it might even survive a fast-moving wildfire.
Yes, it takes water to protect a planted landscape from fire. If consistent irrigation isn’t feasible, you might want to rethink your plantings.
We saw this in eastern Washington this week, where the small town of Malden was 80% destroyed by a fast-moving fire. But some homes were spared – why? Whitman County Sheriff Brett Meyers pointed out “those people that had some green and some buffer around their home were able to maintain their homes.”
Did these houses survive because of a green buffer?
So while it may seem counterintuitive to keep woody debris on your soil, look at the whole system – not just a piece of it. If you don’t have plants anywhere near your house, then bare soil is the way to go. But for planted landscapes, wood chip mulch is part of the solution – not the problem.
Summer is here in the west in a big way. We are just coming off of one of the largest heat waves ever recorded, and while temperatures are down they are not done. Its hot. Depending on where you live your gardens may have suffered. In the East Hurricanes are starting and extreme rains are occurring. I have images of bent over palm trees in Florida. No matter the season, plants respond with their own growth stages providing they are not blow away or burnt up by raging wildfires. Here in Arizona we have had moderately hot weather in my location but the garden is surviving with irrigation. My Iris plants remind me that it is long past time to deadhead and remove spent flower stalks. Deadheading is second nature to most gardeners and other than making the garden look better, you may not realize why you have or have not adopted this common garden practice.
Deadheading involves removing the spent flowers or inflorescences have withered. Sometimes pruning back to a lower leaf or adventitious bud in the case of roses, or completely removing flower stalks in the case of German Iris is required. The immediate result is a neater looking garden and an emphasis on remaining blooms. When the dead flowers are gone the remaining flowers look better the garden is refreshed. Depending on the plant there can be other benefits if deadheading is done consistently and is well timed.
This portion of the flower garden needed deaheading weeks ago. Even though I won’t advantage the plants by deadheading it will look better if I do.
We grow many kinds of plants in our gardens and deadheading has varied physiological impact depending on the subject being pruned. Properly timed, deadheading can extend the bloom of some plants for example Calendula. However, Calendula produces lots of flowers and removing spent flowers can become an enduring task if you have a lot of Calendulas. Deadheading some garden plants seems pointless such as impatiens which just regenerates flowers on its own. Deadheading soon after a flower passes prevents the plant from investing energy in seed development. If the plant has a long enough bloom cycle, so that energy can be put into other flowers then trimming back the flowering stem stems that are destined to fruit production often releases other buds to grow more flowers. Since photosynthate (sugars) flows in plants on a source-sink model, taking away the “sink” or developing fruit allows energy to be used for growth elsewhere in the plant. The trick is to remove spent flowers soon because seed begins to form immediately after flowering and the plant will rapidly allocate its energy to reproduction once the flowers are pollinated.
with dead heads removed this corner of the garden looks a bit better
Not all garden plants respond to deadheading–the number of flowers some plants present is genetically regulated and dead flower removal does not promote more flowering (many bulbs produce only one set of flowers). Other garden plants will re-bloom if given a chance, and with deadheading (no matter what the flowering habit) the garden will look better without the dead flowers. Some bulbs can be deadheaded to prevent seed formation so that the energy is put back into the bulb or bulblets for next year’s display. Many roses will re-bloom after deadheading. This is not a wild-type characteristic of roses but a quality that has been selected for after years of plant breeding.
Deadheading can also be an excellent method of excluding diseases. Botrytis on rose blossoms and petal blight on Camellia are both controlled to some degree by removing infected blooms as soon as they are observed and disposing of them away from the garden.
This bag contains Penstemon with ripe seed heads ready for harvest and seeds for planting somewhere else in the garden.
Sometimes deadheading results in seed collection. Left too long, some plants go to seed but have not yet released their seed. If you want to save seed for propagation, strategic deadheading will allow you to collect seed while redirecting the plants growth patterns for more vegetation or more flower shoots. It is also helpful with our more ruderal garden friends to remove flower stalks to prevent their reproduction and taking over of smaller garden spaces that endure frequent cultivation or soil disturbance. Some plants are desirable but their progeny are a bother….
Ah, summer – vacations (pre-COVID), swimming pools
(pre-COVID), ice cream, vegetable gardens, and, in many places, really high
temperatures. These things all go
hand-in-hand (or at least they did before the pandemic). Many gardeners feel
that the heat of mid-summer goes hand in hand with garden production; those
high temps driving production on those fruiting plants like tomatoes and
peppers. But…..could they be wrong?
We’ve had lots of extra hot days this summer in Nebraska, so it stands to reason that we should have really great production on those garden favorites like tomatoes, right? Then tell me why our extension office has received numerous questions this year about why tomatoes aren’t setting on or ripening. Heck, we even had a Facebook post about tomatoes not ripening in the heat go viral (well, for our standards – 300,000 views/2,000 shares). Could it be a disease? Nope – it’s the heat. High daytime temperatures can have a big effect, but the effects are compounded when nighttime temperatures are high as well.
It turns out that high heat does two things in many of those
fruiting vegetables (and of course fruits) that we grow. First, it inhibits pollen production, which
in turns reduces fruit set. Second, heat
inhibits gene expression for proteins that aid in ripening/maturation of the
fruit. Heat stress also reduces
photosynthesis (Sharkey, 2005) in many different plants, which would slow down
plant processes (such as fruit development and ripening) as it reduces the
availability of sugars to fuel these processes.
So high heat can not only reduce the number of fruits developing on the
plant, but also slow down the ripening process for fruits that have already
set. And if you think that these effects
only happen at super extreme temps, most of the research studying temperature
effects of this nature use a common “high ambient temperature” of 32°C/26°C
for daytime/nighttime temperatures. For us U.S. Fahrenheit-ers, that’s 89.6°F/78.8°F,
which isn’t really all that hot for most of us.
Many studies show that application of this “high ambient
temperature” to crops such as tomatoes, beans, and corn during the
pre-fertilization phases of reproduction (ie – flower/pollen development) can
negatively effect fruit set. The
introduction of Porch and Jahn (2001) gives a pretty good overview of
literature detailing the effect in beans (Phaseolus vulgaris). I’ll sum it up here: heat stress while the
pollen is forming (called sporogenesis) led to pollen sterility and failure of
pollen to release from the anthers (dehiscence). It also led to flower abscission (basically
the plant aborts the flower) and reduce pollen tube formation (how the pollen
nucleus gets through the stigma to the ovule for pollination) when applied
during the period of pollen sac and ovary development. And application during flower opening
(anthesis) resulted in pollen injury (sterility) and reproductive organ
abscission. All of these effects lead to
reduced fruit/seed set in beans. (Interestingly,
heat stress at the ovary development phase also led to parthenocarpy –
basically the pods developed, sans seeds, without fertilization).
However, we get the most calls about tomatoes (they’re the top crop for most home gardeners). Is it the same issue? Yep. Numerous studies (Sato, et al., 2000; Pressman, et al., 2002; Abdul-BAki, 1992) show the same effect in tomatoes. Pressman, et al. (2002) linked the effects on pollen to changes in carbohydrates in the anthers (reduced starch storage and carbohydrate metabolism).
Tomato floral structures
To add insult to injury, high temperatures also slow down or stop ripening of crops like tomatoes. Picton and Grierson (1988) found that 35°C (95°F) temperatures altered the gene expression in tomato fruits – inhibiting the expression of polygalacturonase, which softens cells walls, allowing the fruit to ripen. Reduced photosynthesis would also reduce the availability of sugars for fruit development and ripening.
But there’s hope, both this season and in the long term! The effect on the plants is not permanent. When temperatures drop below that “high ambient temperature” threshold pollen production, and therefore fruit set, will return to normal (as long as the plant is healthy). Sato, et al. (2000) found that pollen release and fruit set resumed within a few days after heat stressed plants were “relieved” and temperatures dropped back into the optimal range of 26-28°C/22°C (78.8-82.4°F/71.6°F). So many of those plants will become productive again (good news for my own tomatoes and beans, which had an initial flurry of production then went on vacation), especially as we head into fall. And efforts are under way to develop and test heat stress resistant cultivars.
This last point may be more important than you realized. These production problems plague many areas
around he world at current climactic norms.
Many fear that increasing temperatures will limit the productive
capacity of many areas of the world that are already struggling. It is easy to see how the difference in just
of just a few degrees can take your veggie production from prolific to paltry.
You can also try to reduce the heat a bit yourself for an immediate fix. Shade cloth can help reduce temperatures a little bit, which may make all the difference in your garden if you’re just slightly over the “high ambient temperature” threshold.
Tomatoes under shade cloth | Source: flickr.com
But in the meantime, if your vegetable garden has taken a summer siesta it will get around to producing again one day. You’ll just have to take good care of the plants in the meantime. And perhaps it’s a blessing in disguise – when its that hot I don’t want to be out working in the garden much, either.
Sources
Abdul-Baki, A. A. (1992). Determination of pollen viability in tomatoes. Journal of the American Society for Horticultural Science, 117(3), 473-476.Porch, T.G. and Jahn, M. (2001), Effects of high‐temperature stress on microsporogenesis in heat‐sensitive and heat‐tolerant genotypes of Phaseolus vulgaris . Plant, Cell & Environment, 24: 723-731. doi:10.1046/j.1365-3040.2001.00716.x
Pressman, E., Peet, M. M., & Pharr, D. M. (2002). The effect of heat stress on tomato pollen characteristics is associated with changes in carbohydrate concentration in the developing anthers. Annals of Botany, 90(5), 631-636.
Sato, S., Peet, M. M., & Thomas, J. F. (2000). Physiological factors limit fruit set of tomato (Lycopersicon esculentum Mill.) under chronic, mild heat stress. Plant, Cell & Environment, 23(7), 719-726.
Sharkey, T. D. (2005). Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, rubisco deactivation, reactive oxygen species, and thermotolerance provided by isoprene. Plant, Cell & Environment, 28(3), 269-277.
This tree suffers chronic drought stress every summer. Why?
It’s the middle of summer, and maybe you’re wondering what’s wrong with your landscape tree (or shrub) that just doesn’t seem to be putting on the growth that you’d expect this time of year. Before you take any “corrective” action, let’s figure out what the problem might be. Here’s a short checklist that we will start with. (NOTE: This is just a start. You can go so many different directions once you have some specific concerns to explore.)
Do you have one of these? If not, you can’t adequately diagnose problems.
Soil information. Have you had a soil test done in the last few years? If so, are there any nutrient toxicities indicated? Has the soil been significantly disturbed or modified in the last several years? Have you recently added any chemicals (fertilizers and pesticides, organic or otherwise) or amendments?
Plant information. When was the plant installed? Was it in a container or in a burlapped rootball? If so, were all materials removed from the roots by root washing before planting?
Planting information. Did you amend the soil (i.e., add anything to the backfill) prior to planting? If so, what did you add? Did you mulch it afterwards? If so, what is your mulch material? Did you ensure that your plant was set at grade in the landscape? (“Grade” means that the root flare is at the soil surface.) Did you water it in well and avoid compacting the soil? Are new plantings adequately irrigated during their first year in the landscape?
Environmental information. Have there been unusual weather events between time of planting and now? Is there sufficient irrigation and drainage?
Symptoms. What are you seeing that concerns you?
Intact clay rootball after 28 years (and yes, the tree died long before this photo was taken).
At least 95% of the landscape failure cases I’ve diagnosed over the last
20 years can be traced back to improper planting methods. You simply cannot
pull a woody plant out of a pot and stick it in a hole. There are three major
factors at play here to consider when rootballs are planted intact:
Think that this root system can straighten itself out? Think again.
The textural and structural differences between the soilless media around containerized roots (or the clay in a B&B rootball) and the soil in the landscape are significant enough that they will impair water, air, and root movement across the interface. This means roots have a difficult time establishing outside the planting hole.
Any structural flaws in the root system created during improper potting-up at the production nursery, such as circling or J-hooked roots, are undetected and uncorrected. And these woody roots will stay in a death spiral after planting.
If you cannot see the root flare of your plant, then you cannot plant at grade. Most trees and shrubs that are buried too deeply will generally fail to thrive and eventually will die.
If you can’t see the root flare, you’ve got a problem. See the next photo.
If you’re like the majority of people who are seeing problems this time of year, you know that improper planting or severe soil disturbance is to blame. But now is not the time to fix it! You’ll need to wait until the fall, when the crown has gone dormant, to dig the plant up and take corrective action. (The “corrective action” has been discussed in this blog before; you can explore the archives or wait for an upcoming post).
These are the roots of the tree at the top of the post. No root flareNo surprise that it’s chronically water stressed in the summer, given this pathetic root system.
What you want to do right now is keep your plant as healthy as possible by mulching with coarse wood chips (not bark) and supplying them with adequate water. You DO NOT want to prune them, because that just uses up stored resources as the plant then replaces pruned material with new shoots and leaves. You DO NOT want to add fertilizer, unless you know that you have a nutrient deficiency (which you can’t know unless you’ve had a soil test. And no, those cute little diagrams of what nutrient deficiencies look like in corn leaves are worthless. You’re not growing corn here.) And DO NOT add any pesticide of any sort, even if you see signs of insect or disease damage on the foliage. With few exceptions, pesticides are broad-spectrum and you will kill beneficial species as well as any possible pests. Opportunistic pests and disease attack stressed plants, and that’s why you are seeing them.
Crown pruning just results in more crown growth. Don’t do this if you are planning to move a woody plant during the current year.
In the upcoming months, I’ll do some follow up case studies that can help you learn how to diagnosis problems. If you’re interesting in having your tree or shrub problem diagnosed and can supply sufficient information (as outlined above) and clear photos, leave a comment on this post and I’ll contact you.
Glass bowls make excellent closed terrariums. This one has been planted for about three years. Episciacupreata. and Begonia luzonensis dominate this planting.
Terrariums are are contained environments that allow culture of plants. They take many sizes, shapes and dimensions and can be sealed or open. At the least terrariums are just plants in a bottle, in their highest form they are cultivated landscapes in miniature. Closed terraria create a unique environment and opportunity for plant growth. The transparent walls of the container allow for both heat and light to enter the terrarium while maintaining high relative humidity and preventing system water loss. Sealed containers combine retained moisture and heat which allows for the creation of a small scale water cycle. This happens because moisture from both the soil and plants evaporates in the elevated temperatures inside the terrarium. Water vapor then condenses on the container walls and eventually drips back onto plants and soil below. A sealed terrarium is ideal for growing some kinds of plants due to the constant supply of water, thereby preventing them from becoming dry. Lowland jungle plants from warm climates will do well. Some cloud forest plants, orchids and bromeliads will not fare well in sealed environments because they require more air movement and/or cooler temperatures. Terrarium culture can allow growth of plants difficult to cultivate even in greenhouses. Terrariums can be displayed to great effect and are an easy method of indoor gardening. Success with a terrarium garden requires an understanding of the container, light, media, and the plants themselves.
My favorite terrarium fern Lemmaphyllum microphyllum (center). On the very bottom is the vining Peperomia prostrata and at the top is a runner of Ficus minima ‘Quercifolia’.
A Word about the Plants
A contained environment is not for all plants. When in a sealed environment, certain plants such as cacti or succulents will grow poorly or in a manner not suited to their habit (lanky or etiolated growth). Problems arise when plants not suited to a small contained environment are used. Plants such as Syngonium, Diffenbachia, and the larger Peperomia spp. look good when planted initially, but will soon outgrow their space–they are not suitable for closed terrariums. The classical “florist” terrarium planted with very young houseplants looks good at first but is completely unsustainable for months or years. A well designed terrarium should grow for multiple years before a complete tear down and replant is necessary. Thus it is necessary to select truly miniature and high-humidity-loving plants for closed terrarium culture. Ferns, sellaginellas, gesneriads, begonias and some peperomias are suited for these conditions. Obtaining truly miniature and humidity loving plants is difficult. Online vendors are the most accessible sources, but also other hobbyists or plant societies can be sources at their annual sales. Nurseries carry some of these plants but the vast array and diversity of rare plants are found on Ebay and Etsy. Many nurseries list plants under the ‘terrarium plants’ search words that are not really suitable, so take care to look for truly small or miniature plants. Perhaps start with the list I have provided at the end of this article for some of the tried and true plants that will work well. Terrarium gardens are not sustainable if you make bad plant choices, you will eventually end up removing plants that outgrow their containers.
The Container
Once you have your plants, you are ready to start. Or you can start before getting your plants and set up your terrarium now to plant later, or in stages, as you acquire new specimens to add into your contained garden. The first consideration is a suitable container. The larger the container the easier it will be to plant, grow and maintain your garden. Larger containers will also allow for a greater diversity of plant types. Fish aquariums may not be the most attractive, but are the most practical in many ways. Because they are rectangular they allow for placement of a light on the lid and they are easy to cover and place on square surfaces such as tables or window sills. Glass containers are preferred over plastic because they maintain transparency better over time. While bottles are attractive, if you can not get your hand inside they can be very difficult to plant and maintain.
Small containers are not optimal but if the plants are small, they can work well. This sundew has been in this container almost for a year
The Media
Lowland, humid jungle plants grow in decomposing organic matter. For our purposes peatmoss is the best medium. It can be amended with fine horticultural perlite (20-30%) or sand. Sand will make a heavier mix, and, if you are doing a large terrarium, mix weight is important. If not, sand is ideal. Also, since terrariums are contained, they may become disease gardens if you are not careful. Therefore I recommend sanitizing your media in a microwave until the media temperature exceeds 160F. Keep the bag closed until the media cools. A turkey roasting or other microwave safe bag works well. Media can be sanitized in a conventional oven–it just takes longer. Media should be moist but not wet when microwaved. Distilled water can be added later to moisten the media after planting. Commercial mixes can be used for terrarium media but care should be taken. Search the blog for my article on potting soils.
Since terraria are sealed environments, you need a reservoir for the water and a filter. Create the reservoir with coarse horticultural perlite (#3) up to an inch thick (the bottom most layer) depending on size of the container –the bigger container, the thicker the layer. Cover the perlite with activated charcoal. Fish aquarium charcoal or horticultural charcoal from the nursery is fine, but NOT charcoal briquettes. The charcoal layer just covers the perlite. Now add soil. Slope the soil from thin in the front to thicker in the back. You can also add wood, sticks, and rocks to make interesting landscapes. They should all be sanitized in the dishwasher or boiled or microwaved until sterile. After placement of soil, rocks and sticks are ready to plant. Place larger growing plants in the center and rear and small vines up front.
Your container should be sealed either with “cling tight” plastic wrap or glass. I prefer glass for most applications.
Light
While terraria can grow in window light, especially north light, it is not optimal for most plants and they will grow slowly. You can’t place terraria in direct sunlight or the plants will “cook” because closed terraria can’t dissipate heat that rapidly. The old standard for light sources is fluorescent tube fixtures, but they have been supplanted by Light Emitting Diode (LED) technology. Grow-light LED fixtures are expensive, but provide some performance differences. Terrariums are not crops and we don’t want them to grow too fast so find an affordable light source that works for you. LED sources are nice because they are not bulky and do not add large amounts of heat. A bit less light or less optimal wavelengths of light are ok because we want to sustain plant growth for a long time, not grow the plants to the edge of the container real fast and have to prune or start over. The Costco brand shoplight LED fixture is perfect, but it is four feet long. Smaller LED fixtures would be appropriate for smaller containers. The Costco fixture is perfect for a 60 gallon fish tank. White light works well and looks best. Red and blue LED fixtures change the way we see the plants and are not best for viewing. Light should come from above so plants will appear to be growing normally. If the terrarium is placed near a window it will need to be rotated to keep plant growth even.
Moisture
Moisture is critical in terraria. The growing medium should hold a shape when squeezed but not be saturated when you plant. After the terrarium is planted, you can “water it in” with a dilute -1/4-strength fertilizer solution mixed into distilled water. Watering amounts will vary by container size. Water should penetrate soil to the depth of roots and some should enter the reservoir. No more watering is necessary again until some time later when plants have grown considerably—usually months later. I usually water the glass to clean it from the initial planting with a turkey baster. At some point in the future, months not weeks, the soil may dry as growing plants use up water. When this occurs, water again with another dilute fertilizer solution. Do not over water your terrarium or bad things will happen. Also resist misting or spritzing as this will cause leaves to rot and is not necessary in a sealed environment.
Pruning, Replanting and Maintenance
Some of your chosen plants may outgrow their space. Some like Ficus minima ‘quercifolia’ will just overgrow everything, the same can happen with common Sellaginella sold in nurseries such as S. brownii. You should plan on pruning back the plants and making cuttings or planting other terrariums with the prunings. Cut begonias below a node or along the rhizome. Rhizomatous ferns can be clipped or dug and planted elsewhere. If you have to remove a really big plant it will leave a hole. New sterilized mix should be added to fill the hole along with the new plant occupant. Removal of flowers, mushrooms (should they form) and dying leaves is important. They will cause rots on plants they fall on. Sticks are usually always a problem since it is very difficult to kill mushroom fungi living in them. Mushrooms are mostly non-toxic to plants, but they drop spores and these lead to rot on sensitive begonias and ferns. Clip back Begonia, EpisciaSellaginella, Peperomia or Ficus to prevent them from overgrowing other plants.
Recommended Plant List
If you can find them, here are some recommended plants for terrariums.
Begonias B. prismatocarpa B. prismataocarpa variegata B. versacolor B. ‘Raja’ B. ficicola B. exotica
Ferns Edanoya spp. Humata parvula Lemmaphyllum microphyllum Microgramma spp. Pecluma pectinata Tectaria spp. Quercifelix zelanica
Others Peperomia prostrata Sininngia pusila and all its variants Episcia spp. (there are many, I like the pink ones) Saintpaulia (african violets-only miniatures) Sellaginella erythropus Sellaginella spp. (there are many kinds, S. brownii is most common) Ficus minima ‘quercifolia’
It’s not my week to post on the blog, but this is a PSA for California residents. Having visited the Capitol grounds in Sacramento, I find it important to make others aware of the plans to remove a number of large and historically important trees for the purpose of building a parking garage and expanding the Capitol building space.
I’m not a California resident, so in a sense it’s none of my business. But I am an urban horticulturist, and an arborist, and committed to preserving trees especially in urban environments. These trees are irreplaceable unless you want to wait a few hundred years. The plans to “relocate” some of these large trees are probably not realistic given the size of the specimens.
More importantly, this is public space and the public should be actively involved in discussions. But the process has been secretive and under the radar of a public more concerned, and rightly so, about COVID-19 and all the associated fallout from the pandemic. But it’s not too late.
Please share this post with California residents who have should have a say in how their land should be managed.
More importantly, you should call AND write to your own California legistator at this website findyourrep.legislature.ca.gov, as well as the two Legislative leaders who can really pause the project and guide its re-planning: Senator Toni Atkins, President pro-Tempore of the Senate, 916 651 4039 and senator.atkins@senate.ca.gov. UPDATE: This email does not appear to work. Try using this form. Assembly Member Anthony Rendon, Speaker of the Assembly, 916 319 2063 and speaker.rendon@assembly.ca.gov
While most of the country is in the
middle of a heat wave and the mercury is creeping past 100F on many
thermometers, lets do a little exercise to help you feel cool as a cucumber
(though not straight out of the garden, those cucumbers would likely be hot). I want you to think about a crisp September
morning. You’re out walking through your
vegetable garden and you stop to appreciate a big, emerald green head of
broccoli. Just a few feet away, stalks
of Brussels sprouts, those miniscule cabbages that have somehow overcome years
of revulsion to become sexy and desirable (they must have a good agent) shoot
up like skyscrapers around the rest of the plants. Lush lettuce fills in a bed nearby, and some
cucumbers and beans that you planted late are looking as fresh as a newborn
chick.
Sounds beautiful, doesn’t it? Well I’m here to tell you that you can
actually make this a reality. You can
have a super productive garden this fall, and for most areas of the country the
time to start planning and planting is now.
Right now, when a cool refreshing fall morning seems as far away as a
trip to the moon. Of course, the exact
timelines and planting schedules differ by region due to the length of growing
season, but most places in the US (and the northern hemisphere) can start
thinking now about planting crops for the fall.
For exact timing in your area, you may want to connect with your local
extension system for gardening guides.
While many experienced gardeners may
know this and practice fall garden planting, there’s a lot of people out there
who have yet to have the pleasure. And
given the huge number of first time (or first time in a long time) gardeners,
these garden basics might be helpful to get the most out of those pandemic
plantings.
In fact, fall is one of the best times of the year to garden. Aside from cooler temperatures making it more pleasant to garden, there’s often less pressure from diseases and insects to ruin crops. In addition, many of those cool season crops, like the ones I mentioned above, actually are more productive in the fall than if planted in the spring. Even though they get a hot start in mid- to late- summer, the cooling temperatures of fall around the time many of the crops come into maturity extends the harvest period and improves overall quality of the produce. You also have the benefit of removing some of those spent and diseased warm season plants and swapping them out for something fresh and new– a garden revival of sorts.
Swiss chard and leafy greens are great additions to the fall garden
Unfortunately, since fall vegetable gardening isn’t as widespread as planting summer gardens, plants and seeds can often be hard to find when it is actually time to plant (so planning ahead is helpful). Mid-summer is usually the time for most regions to start seeds for those slower growing cool season crops like broccoli, cabbage, cauliflower, and their kin. They can be started indoors, but the need to do so isn’t as great as it is for those warm season crops we start indoors in late winter. You can start them in pots/flats outdoors as long as you have somewhere that isn’t so hot and sunny that they’ll be continually drying out (some shade would help). They should be ready to transplant by late summer. You can skip the seed starting/transplanting if you want to try direct seeding into the garden, but as they say “your mileage may vary”.
Some of the fast maturing warm season (frost tender) crops are
also good candidates for a mid-summer planting as a way to refresh the garden
if you have space for it. Beans are a
good candidate for late-summer planting, but you’ll need to make sure they are
a fast-maturing variety (there’s a wide range of maturity times in beans). Bush
beans are usually the quicker growers. Pole beans and lima beans usually take a
longer period, so those don’t do as well later in the season for places that
have frost and freezes.
It is also a possibility to squeeze in a late crop of cucumbers
or summer squash as well. This can be good if your cukes and squash succumb to
disease, squash vine borers or cucumber beetles. Planting late can often mean
that you are missing the primetime for specific pests. For example, squash vine
borer adults actively lay eggs in the early season but largely disappear later
on. A late planting means you could miss
them entirely.
Fall is the best time to grow leafy green vegetables.
Lettuce, which does not fare well in the summer, thrives in the cooling
temperatures of the fall. Other leafy greens, such as chard, spinach, and
kale are also winners in the fall garden.
Many of the root vegetables, such as turnips, carrots, beets, and
radishes are also part of the fall garden revival. You’ll want to wait
until temperatures have chilled a little to get these started, but not so late
that the season ends before you get good growth.
You gotta know when to sow ‘em
The key to fall planting is to know how many days it takes for
the crop to mature. Check out the seed package or the plant tag — there should
be a time to maturity on there. Just count backward from the first frost date.
Be sure to add a few weeks to account for slower growing in cool weather and to
allow for a reasonable harvest time.
For example, if I wanted to plant a late crop of beans, I might
select the cultivar ‘Contender’ which matures in about 55 days. I want to add at least a few weeks onto that
for maturity and harvest time, so lets say I need 75 days (I can go shorter if
I want to accept the risk of an early frost).
Let’s also say that my first frost date in the fall is October 20. Counting back 75 days from October 20, I get
August 6 – I should plant my beans no later than that date to get a harvest.
Most of the cool season crops can tolerate a frost (and some even a freeze) so their growth dates can extend beyond the first frost date. You’ll just want to have them mostly grown and close to maturity before it gets cold enough to stop their growth. I covered frost and freezes and which crops can survive those cold temps in this previous GP article.
You can give yourself a little more time if you plan on
incorporating a season extension practice in the garden. Using a row cover or
constructing a low tunnel can give you several more weeks of growing time. It
can be possible to enjoy a fresh tomato or green beans straight from the garden
on the Thanksgiving table, or some fresh broccoli or kale at Christmas even in
some of our colder regions. But it all starts with a little planning in the
heat of summer.
And if you choose not to plant a fall crop, I would suggest using a cover crop in garden beds as you remove this year’s plants. A cover crop will help keep weeds to a minimum and preserve soil structure and nutrients through the winter. Winter wheat, rye, and crimson clover are good winter cover crops. Next spring you just cut them down and till them in if you’re not practicing no-till (and you should be if at all possible). For annual cover crops, you can usually cut them down or break them over and leave them in place as a mulch. You can also pull them up and compost them to add directly back to the garden, especially if (since it is hard to till or mow in a raised bed). This GP article is an oldie but goodie for using cover crops in the vegetable garden.
Two years ago I installed a pollinator garden in early July. This goes against my recommendation to install plants in the fall, when roots have longer to get established and less stress is felt on the rest of the plant. But I wanted to see what would happen if I was careful to mulch well and keep it irrigated. Oh, and did I mention I was going to root wash every one of them? (Be sure to look at that process in the link from 2018.)
Southwest garden, October 2018
Southwest garden, July 2019
I reported on progress last year, and this year shows even more vigorous growth by nearly all the plants. Two of the three ‘Bandera Purple’ lavender died over the first winter, as they were marginally hardy (USDA 7-10) for our area. One straggler remains in the lower right hand corner of the photo below. The Agastache ‘Acapulco Red’ and the Verbena ‘Homestead Purple’ were planted near the front of the beds on both sides and while they survived the first year, they are now gone. My guess is that our cold snap in February 2019 wiped out those plants that were in less protected locations. Perhaps we’ll fill those spots in later with something more cold hardy, or just let the escaped Viola tricolor continue to colonize bare spots.
Overall, the garden is wildly successful in attracting hummingbirds and a variety of native bees and other insects.
The southwest garden is being colonized by violets that have hopped out of a nearby container. Wood chip mulch keeps the soil cool and moist.The southeast garden with its invading strawberries (soon to be relocated). The tiny lavender in the back right corner is a rescue plant.
I still have a little work to do – I’m relocating the strawberry adjacent to the southeast garden so it stops invading the perennial bed. But after that I’m calling this garden finished.
