What’s wrong with my plant? You’re not going to find pat answers.

As many of you know, the Garden Professors host a Facebook group dedicated to the discussion of science-based practices for gardens and landscapes. (Side note – if you haven’t joined us please do!) Recently we’ve had a spate of “what’s wrong with my plant” posts, usually focusing on some leaf issue and little other information. And far too often an eager group member will jump in with a fertilizer recommendation.  So today’s blog post has two objectives: explaining why you can’t reliably diagnose problems from a picture of suffering leaves and why blanket fertilizer recommendations should be avoided.

To illustrate the problem with armchair diagnosis, consider this photo below.

Interveinal chlorosis in Rhododendron.

Now there are two ways to ask a question here: the first is “what’s wrong with these leaves” and the second is “what’s wrong with my plant.” We can easily answer the first one: there is nutrient deficiency in the leaves, most probably iron or manganese. But that does NOT mean there is a deficiency in the soil. So we can’t address “what’s wrong with my plant” because we don’t have enough information.

How can we determine what’s wrong? My first question to the poster is invariably “have you had a soil test?” Soil test results will indicate whether the element in question is actually deficient, and will provide levels of other nutrients that could interfere with root uptake.  If there’s no deficiency of the nutrient in question, then adding fertilizer is not going to help! And adding fertilizer unnecessarily can create further soil nutrient imbalances and contribute to environmental pollution.

Lots of iron – no deficiency here!

Once we have the soil test results, we can then begin to address “what’s wrong with my plant.” But not from the original picture. (If you are curious about what else could be causing this problem, check out this blog post from 2011.)

Let’s try another. Consider the leaves in this photo:

Another unhappy Rhododendron

We now know to ask “what’s wrong with these leaves?” Ignore for now the deficiencies in the older leaves and look at the size of youngest ones compared to the older. The answer is fairly straightforward here: there was too little water available when the newly emerging leaves were expanding. Leaf expansion depends on turgor pressure – the higher the turgor pressure, the larger the leaves get. Once expansion stops, protective plant biochemicals are laid down which prevent further expansion. By comparing the youngest leaves to the leaves from previous years, you can see that they are significantly smaller. But why?

Again, we need more information before we can answer “what’s wrong with my plant.” Was there too little available soil water during leaf expansion? It’s possible, but this example is from western Washington State, a climatic region with wet springs. Most likely there is an issue with the roots. My first question with these cases is “can you easily move the plant in the ground?” This is my “wiggle test” – a way to determine if roots are established. In this case – and in nearly every case like this that I’ve seen personally – the roots are NOT established. Often this is because the plant (1) was not bare-rooted at planting and/or (2) was planted too deeply. Without decent root establishment there is not enough water uptake to support full turgor in expanding leaves.

It may be quick and easy, but “pop and drop” is not a good planting method.

Lack of an established root system also account for the interveinal chlorosis you can see in the oldest leaves. These leaves are fully expanded, probably because the plant was still at the nursery when these leaves emerged. But their color is off. A root system that doesn’t supply sufficient water for leaf expansion is by default not going to provide sufficient nutrients, either.  Adding fertilizer to this plant is not going to help! It needs to be dug up and replanted correctly or replaced. It is never going to thrive under the current conditions.

Armchair diagnosis can be accurate and fun if you follow a set of guidelines to extract more information. But simply recommending a fertilizer based on leaf appearance is neither science-based nor environmentally responsible.

No. Just….no.

“Fun-guy” in your Mulch

By Jim Downer

Fresh wood chips!

As many avid GP readers are aware, mulches are a common horticultural tool that help gardeners maintain soil moisture, nutrient content, weed suppression and assist in disease prevention.  The best mulch is made from chipped tree trimmings wastes and has a large wood content.  Coarse “arborist chips” mulch is fast becoming one of the most frequently sought after mulches for residential landscapes.  It is very effective and contributes to significant soil improvements over time.  As chip mulches decompose, the fruiting bodies of fungi are often seen growing up through mulch.  Sometimes, as gardeners work in previously mulched beds, they see mycelium or cordons (rhizomorphs) of mulch fungi growing through the mulch.  Some gardeners are not fond of finding mushrooms growing in their mulch and have termed these as “nuisance fungi”.  There have even been extension leaflets on nuisance fungi and how to rid them from your garden!!  Fungi are a natural part of mulch breakdown and their presence in mulches is desirable!

Phanaerochaete chrysorhiza invading Eucalyptus globulus mulch

The first encounter many gardeners have with mulch fungi is when they see “mold” growing in the chips or at the interface of mulch and soil.  Mold gets a bad rap with many homeowners when they find it after water damage in their house, so perhaps they assume it is also bad for their gardens.  Mold abatement in homes has become a specialized industry, and while the spores of some fungi can be human pathogens, fungi are not to be feared in gardens unless your immune system is damaged or otherwise compromised.   Unlike houses, gardens are a good place for fungi to grow and thrive.

Fungi absorb water and nutrients from their hyphae which grow into their food (mulch particles).  The absorptive lifestyle of fungi is unique.  Since fungi have no internal digestive systems, they rely on excreting enzymes outside their bodies and into their food which breaks down the substrate so they can absorb it.  By doing so, they also release minerals, sugars, amino acids and many other compounds for other microbes and plants to utilize.  Fungi are mostly saprophytes or decomposers, and their role is to release organic nutrients to soil so they can be recycled.  This is why mulches are so beneficial to woody plants.  Without fungi, forest litter would pile up largely undecomposed because bacteria and other microbes are less efficient in breaking down cellulose.   Some fungi are mutualistic partners with woody plant roots.  Ectomycorrhizal (EM) fungi rely on interactions between trees themselves and the litter or mulch layers under trees.  Fruiting bodies of EM fungi may appear as mushrooms or puff balls in or next to mulches.

Lepiota spp. an ectomycorrhizal species
Amanita muscari , another ectomycorrhizal species. Just don’t eat it.

 

 

 

 

 

 

 

 

Sometimes fruiting bodies (mushrooms) push through mulch, but are not the result of mulch presence.  Pathogens such as Armillaria mellea (oak root fungus) can form through mulch layers or turfgrass, but they are fruiting off the dead roots of their tree host.  Similarly, the inky cap mushrooms (Coprinus spp.) often grow saprophytically on dead roots (they are not the cause of root death) and will push through litter layers.  Coprinus are good indicators that a tree has dead roots.  Coprinus is not a plant pathogen, and mulch does not increase prevalence of pathogens in landscapes.  As we have discussed many times in the blog, mulches are unlikely to spread or support plant pathogenic fungi.

Coprinus spp., which feed on dead roots

Another way to view the role of fungi is the chemistry that they facilitate in soil.  Mulch is organic matter, which has a high concentration of carbon.  Carbon is transformed from a solid form into a gas – carbon dioxide – through the action of microbes (mostly fungi).  So oxidation of carbon is driven by fungi growing through their substrate (forest litter in forests or mulch in gardens).  In mulching systems this is a slow process taking a few years.  In composting systems it is rapid, taking months with the added energy of mechanical turning etc.   Slow decomposition of organic matter is useful, as the benefits of mulch in suppressing weeds, slowing evaporation from soils etc. are maintained over time. Slowly oxidizing carbon means that it will be around longer, creating less greenhouse gasses than in the composting process.

In publications that recommend ways for “dealing with nuisance fungi” it is suggested to let mulch dry out, which stops the action of the fungi.  This is one of the most harmful things that can be done for active mulch zones.  Killing the fungi in mulch also stops their oxidation of carbon, subsequent nutrient release and support for the high microbial activity in mulches that benefit both plants and disease suppressing fungi that plants rely upon to maintain their health.  While fungi can reactivate when dry mulches are moistened, their biomass is damaged by severe drought which also injures plant roots as well.

All good things come to an end or as our physics friends say, “Entropy increases!!”  So as labile (easily metabolized) carbon is used up in fresh mulches, fungi go into spore bearing or reproductive phases and begin to make fruiting bodies.  As long as there is labile carbon, fungi will thrive and grow mycelium and hyphae into their food.  When carbon is being used up (or when there is sufficient mycelium), fruiting bodies start to form.   To maintain these processes, it is important to add fresh mulch over the old decaying mulch.  Once or twice a year depending on temperature and moisture levels.  Along the way, some mulch may develop fungal fruiting bodies.  Fruiting bodies may resemble mushrooms, puff balls, earth stars, bird nest fungi, or simply resemble paint that has been splashed on the wood chips.  They are only trying to survive by developing spores which will later spread onto fresh mulch materials.  Most mulch fungi have very ephemeral fruiting bodies, so even if they are seen to be a “nuisance”, they will only be around for a very short time before they also decompose and become part of the remaining mulch layer or soil.

Ceraciomyces tessulatus, a paint-like fungus

One very common group of organisms seen in mulch and mistaken for fungi are the slime molds.  They are not related to fungi, but do develop spores and have a mobile (plasmodium) phase where they can be seen to slowly move from one spot to another.  Eventually, when the plasmodial stage is done feeding, the sporangial phase is made and they turn into spores.  The most commonly encountered slime mold in mulch beds is the dog barf fungus, a slime mold called Fuligo speticaFuligo is dramatic because it can appear overnight and is large (a patch of the sporangium can be several inches across).  When kicked, Fuligo bursts into dark spores that will fly up into the air.  Slime molds are also saprophytes and live on the decomposing organic matter in mulch.  They pose no threat to humans or garden plants.

Yellow slime mold, aka dog vomit fungus (photo from Wikimedia)

Fungi in the mulch are a good thing and indicate that moisture, temperature and organic matter are at the correct levels for high microbial activity!  This is what creates a healthy soil and ensures healthy garden plantings.

Native vs. nonnative – can’t we all just get along?

Probably the most contentious gardening topic I deal with online is the native vs. nonnative plant debate. This, unfortunately, is a debate that is more based in emotion than science, and I don’t intend to stir that pot again. We’ve discussed it on this blog before (you can find a list of them here), and I’ve published both a literature review and a fact sheet on the science relevant to tree and shrub selection. What I want to do in this post is compare two research papers, both in peer-reviewed journals, that come up with dramatically different conclusions.

The first has been getting a lot of publicity on the web and in social media. It was published just two days ago, but because of widespread PR prior to release it appears over 37,000 times in a Google search. The title “Nonnative plants reduce population growth of an insectivorous bird” – and much of the prerelease publicity about the article spells doom and gloom. It’s a message that gets traction.

The second was published a year earlier and is entitled “Native birds exploit leaf-mining moth larvae using a new North American host, non-native Lonicera maackii.” It appears 194 times in a Google search, even though it’s been available for over a year.

Amur honeysuckle (Lonicera maackii)

The reason I’m singling out these two articles is they have completely different messages – and one of them is not being heard as loudly as the other. The first focuses on a single bird species, the Carolina chickadee (Poecile carolinensis) and its diet in urban landscapes. Their conclusion: “…properties landscaped with nonnative plants function as populations sinks for insectivorous birds.” Thus, any gardener who happens to use introduced ornamental plants in their landscape is made to feel guilty for starving their insect-eating birds. (As an aside with my manuscript reviewer hat on – this statement has no business being in an abstract as it overextrapolates the research on one species to include ALL insectivorous birds.)

Carolina chickadee (Poecile carolinensis)
Black-capped chickadee (Poecile atricapillus)

 

 

 

 

 

The second article has a different focus. It reports the feeding of black-capped chickadees (Poecile atricapillus) on the larvae of a leaf-mining moth (Phyllonorycter emberizaepenella). While leaf miners are common food items for chickadees, the point of this article was to document the host of the leaf-miner – a nonnative and particularly invasive species of honeysuckle (Lonicera maackii).

Honeysuckle leaf miner (Phyllonorycter emberizaepenella)

 

Honeysuckle leaf miner damage

 

 

 

 

 

Chickadees as a group are particularly adept at finding and consuming leaf miners, whose tunnels normally protect them from insectivorous birds. Chickadees move along branches,“examining leaves both above and below them; the chickadees sometimes scanned by hanging upside-down.” This makes it easier to find and extract leaf-miners, as the underside of the leaf is easier to tear open than the surface. And in fact this behavior is reflected among other species of chickadee and leaf-miner: “Similarly, in 15 years of study, Connor et al. (1999) never observed species other than Carolina chickadees (Poecile carolinensis) feeding on the larvae of the gracillarid Cameraria hamadryadella [oak leaf miner].” While these are not the same species of leaf miner studied in this paper, the point is that chickadees eat leaf-mining insects. And leaf-miners can obviously adapt to new food sources, including introduced plants. This is basic ecological science.

Oak leaf miner damage
Oak leaf miner (Cameraria hamadryadella)

 

 

 

 

 

 

Neither Craves’s article (the second of these two articles) nor that by Connor et al. (cited within Craves’s article) are cited by Narango et al. (2018 – the first article), even though both are certainly pertinent to the topic. But they don’t fit the narrative – which is that introduced plants are not good food sources for the insects that chickadees eat. So they are left out of the discussion, which by default is now biased – not objective. Not science-based.

And I don’t have a good answer to the obvious question – which is why we continue to demonize noninvasive, introduced plants in the absence of a robust body of evidence supporting that view.

 

Root washed perennials – 3 months later

You’ll recall that in July I posted about root-washing perennials before planting them in the middle of our typically hot and dry summer in the Pacific Northwest.  I wanted to update everyone on how they performed now that we’re heading into our cooler and wetter fall months.

Just to remind you, here’s a photo of the garden right after planting:

South-facing pollinator garden

And here is the same garden, 3 months later:

Made it through the summer!

No plants died; in fact, as you can tell, they all thrived. They were watered twice a day during the hottest months and now are rain watered only.  (The underlying soil is an excessively drained glacial till, which is why we water frequently during esablishment and why we don’t worry about the drainspout. Water doesn’t stay around long.)

I used no fertilizer. I did add the soilless media from the root washing to the top of the soil and then covered with woodchip mulch.

There was, of course, a period of about 6 weeks post planting where there was no above-ground growth. But all of these plants retained their flowers, which kept our bees and other pollinators (butterflies and hummingbirds) happy. In August, the plants started to put on new growth at a furious rate now that roots have established.

Native bumblebee on salvia.

Take some time and go back to the original post (which is linked in the first sentence. Look at the roots – before and after washing and pruning. Now look at the results.

Why wouldn’t you plant this way?

Set your roots free on this Independence Day week!

We’ve discussed barerooting/rootwashing trees before, and research on this controversial topic continues. But what about smaller shrubs and woody perennials? What about herbaceous perennials? Basically, what about PERENNIALS???

Lobelia laxiflora

I’ve always made a practice of rootwashing everything except for annuals. They don’t last long enough to suffer the perils of potbound plants. But many gardeners are nervous about disrupting more fragile root systems. Let’s see what happens when we do.

Lavandula ‘Winter Bee’

A little context: we’ve just moved to our family farm, which has AMAZING spring flowers that the bees love. But once those are gone…there’s nothing. I was desperate to provide some food for bees and butterflies, so it was off to the nursery to shell out a few hundred bucks for the beginnings of our south-facing pollinator garden – a previously barren spot left after construction of our porch.

Lavandula ‘Bandera Purple’

So I bought Lavandula stoechas ‘Bandera Purple’ and ‘Winter Bee’, Salvia ‘Caradonna’, Agastache ‘Acapulco Deluxe Red’ and ‘Blue Boa’, Erysimum ‘Winter Passion’, Verbena ‘Homestead Purple’, and Lobelia laxiflora. I depotted and soaked them in a water bath, using a gentle hose setting to loosen up media in the center. For most of these plants, a massive root disk at the bottom of the pot had to be cut off like a giant slice of salami. If necessary, I “tickled” the remaining rootball to work out the rest of the media.

Here is Erysimum ‘Winter Passion’ potted, depotted, and washed.

Not too bad…

The Agastache and Verbena cultivars were also in pretty good shape, much like the Erysimum. Just a gentle washing and tickling was enough to remove all the media and reveal the roots.

Here is Salvia ‘Caradonna’ potted, depotted, and washed, and Lobelia laxiflora potted, depotted, and washed.

Apart from the root Frisbee on the bottom of each pot, the roots were confined to the center of the pot, pretty much where they had been in their previous container.  So question number one for all of you gardeners – why would you want to dig a hole to plant all of that media (which is nothing like your soil)? My answer – you don’t! Keep that good organic material as part of your topdressing.

Here is Lavandula stoechas ‘Bandera Purple’ potted, depotted, and washed;

and here is Lavandula stoechas ‘Winter Bee’ potted, depotted, and washed.

I have to take time out for a special rant about the lavenders (retailing at $19.99 and $12.99). Look at the root mass of the ‘Winter Bee’. It’s entirely unacceptable. The woody roots are in the shape of the liner pot from transplants past. News alert: these systems do NOT self-correct. They must be straightened or pruned to regain a natural structure. The ‘Bandera Purple’ – the more expensive of the two – was actually three plants in one color-coordinated bowl (“Go ‘Colour Crazy’ with matching pots and flowers”!). Fine by me – I just got 2 free plants. (By the way, this is nothing new for me – I’ve written about it previously here and here.)

Another upside is that hole digging was short and sweet. Holes were just deep enough to accommodate the root mass and wide enough to allow roots to be spread. Soil was added and watered in. The leftover organic media was used as the first layer of topdressing, followed by a fresh woodchip mulch. And then irrigation to soak the mulch well.

Salvia ‘Caradonna’

It’s important when you rootwash plants to provide optimal soil water every day, particularly when it’s hot and sunny (as this south-facing garden is). Even with the gentlest root washing there will be a loss of fine roots. But the continuity of the soil system means that the soil around the roots will be just as moist as the rest of the bed. Roots left in soilless media quickly dry out. Yes, I had afternoon wilt on many of the taller plants during the first week or so, but they recovered every evening. The wilt has become less noticeable since then.

Agastache ‘Acapulco Deluxe Red’

So here’s how they look 3 weeks after planting (sunny day, about 80°F). And I’m happy to report that not only birds and butterflies but hummingbirds have been visiting our pollinator oasis garden. And all those single photos scattered through the post? They are all close-ups from this garden – taken just minutes ago.

South-facing pollinator garden

(Question number two for gardeners – what are you waiting for?)

 

 

Bot-strosities

Those of you who are Stephen King fans will remember the Lobstrosities from the Dark Tower series: bizarre creatures that were part lobster and part scorpion and with the nastiest parts of each on either end.

Deadly but delicious

Botstrosities are bizarre plants that aren’t deadly but still assault the senses of those who are unfortunate enough to find them. Here’s my collection – maybe you have others to add?

First up are a classic favorite  – the GMOs (Glue Modified Organisms). Why bother with years of hybridizing when you’ve got a glue gun?

Strawflower cacti
Not exactly subtle hybridization

Everyone knows Cosmic Crisp apples. Now we’ve got Kosmik Kactus! Never mind they aren’t cacti. What I can’t wait for is these aloes to develop “glistening white” or “golden yellow” spines.

Definitely some alien species we could do without
A rainbow from hell

Continuing the unfortunate trend of spraypainting plants, here are some for your favorite football fan (assuming their team is the Seahawks). Question: do other regions have spraypainted heaths in their team colors?

Now this Calluna vulgaris is truly vulgar

And do look forward to metallic jades for the winter holidays!

The perfect gift for the plant lover you hate

Spray painting too obvious for you? Well, how about surgically altered orchids? If you can’t figure out how the flowers developed this garish blue mottling just look closely at the stem.

They might as well be plastic – unnaturally colored and staked upright
Yep, that’s an injection site

We certainly wouldn’t sell spraypainted birds or kittens with bows glued on their heads. Just say no to these horticultural horrors!

Do your homework before hiring landscape help!

(A guest post by Rich Guggenheim. You can see Rich’s bio at the end of this post.)

When it comes to shopping, my friends all know it takes me a long time to make a decision. I methodically research out what I want. Then I narrow it down to a few items. After I look over my choices carefully, I may go home to get on the internet and look at consumer reviews; I may go from store to store and check out prices. I look for quality and I look to make sure I am getting a product that is worth the money I am spending on it. I want to make sure my investment will last. Sometimes, my shopping experience will last hours, days, or in the case of a car or computer, it could be months.

My yard is no different. When I need yard work done, such as lawn aeration or tree trimming, I am insistent on high quality work. As a homeowner you are the first and the last line of defense when it comes to making sure that a quality job is done, and done correctly! Knowing what to expect in landscape maintenance and being armed with a small amount of knowledge as a consumer can play in your favor.

Always hire a certified professional to do your work. Would you seek medical advice from an individual who was not licensed to practice medicine? Of course not! Why then would you do it with your yard? I recommend that you check into the individual or company before hiring them. Do some homework. How have they been trained? Where is their certification from? Are they insured, licensed, and can they provide you documentation? Are they registered with the Better Business Bureau? If so, what is their rating? Drive around and check on some of their previous work. Is it the kind of quality you would want in your own yard? Ask for references. Ask questions! This is, after all, a job interview for the contractor. Just because they are the cheapest does not mean they should get the job, and just because they slap a business magnet on the side of their pick-up truck does not mean they know what they are doing!  In the following I will be talking with you about what to look for when hiring a contractor to do yard work and how certain procedures should be done. Armed with this knowledge, you will be better able to ensure the work done in your yard is of the quality you deserve for the money you pay.

Lawn aeration is perhaps one of the best things that you can do for your lawn. Done twice a year, once in the spring and once in the fall, core aeration combats soil compaction. Soil compaction is a problem in nearly 80% of all landscapes. In addition, aerating your lawn helps combat thatch accumulation and reduces the amount of water you need to apply to your lawn. The reason for this is because when your soil is compacted oxygen and water can’t penetrate into the soil. Fertilizer can’t get penetrate the soil either. As a result, roots are often shallow, and the lawn will need more frequent irrigation. (1, 2, 3, 4)

Core aeration removes small plugs, about 1-3 inches long from the soil. A single aeration using a machine with 1/2-inch diameter tines removes as much as 10 percent of the thatch if enough passes are made to achieve average 2-inch spacing between holes. Remember the key is 2-inch spacing. This may mean that multiple passes on the lawn are required. This small investment of an extra $10 will pay dividends in the end.

What do you do with the cores after you have had the lawn aerated? That really is a personal decision. Some people do not like the little plugs being left on their lawn, although there may be benefits to allowing them to disintegrate into the lawn again.

If you do decide to remove them, they are great for the compost bin. Other options may be to power rake the lawn after aeration, watering, or simply running a lawn mower over the lawn after you aerate (although this practice will cause the blades on your lawn mower to dull). Once you have aerated your lawn if you need to reseed, this is the optimum time to do it. The best part of reseeding now is there is no need to top dress the lawn, as the lawn seeds will have nice little holes in which to germinate!

Another type of aeration being marketed by many lawn care companies these days as a replacement for core aeration is liquid aeration. While different ingredients make up this popular lawn service, the main ingredients seem to be liquid humates (organic matter) and sodium lauryl sulfate (soap). These are nothing more than snake oil remedies and are no substitution for the real deal of removing the plugs from your lawn by core aerating. There is no scientific research which has shown chemical aeration to be effective. You may as well throw dirty dish water out on your lawn. (5)

The thing to remember from all of this is that you want to have your lawn aerated twice a year; in the spring, and again in the fall. The plugs removed should be 2-3 inches long, and on 2 inch centers, which may require multiple passes on your lawn.

Tree pruning is something I take seriously. It is a science which should not be left to a novice and is far more than could be covered in one article. For me, spotting a bad tree pruning job is as easy as spotting a bad haircut. The only difference is a bad hair cut grows back and has no adverse side effects on your health. However, a pruning job can have enormous effects on the health of a tree, either for good, or for bad. When you hire an arborist, make sure they are ISA certified, licensed, and insured. To find an ISA certified arborist, visit their website.


The key points for a good pruning job really come back to structurally pruning the tree correctly when the tree is young. Improper or lack of pruning when the tree is young can greatly increase the likelihood of tree failure when the tree is older. Cuts on branches larger than 4 inches increase the possibility of decay and disease. If possible, prune trees when the branches are smaller than 4 inches in diameter.

When pruning trees, it is important to prune the branch back to the branch collar. Don’t leave stubs, or what I call “hangars” where you can hang your coat. Leaving these nubs will cause decay and disease to move into your tree.

The last key component to pruning is to always remove a smaller branch back to the parent branch, never the other way around. When you remove a parent branch, unless the wood is dead, you greatly increase the risk of beginning the downward spiral of death and decay in the tree. While this is great for less reputable tree-trimming companies who will have to come back year after year to remove an ever-increasing amount of dead wood from the canopy of the tree, it is hard on your pocketbook; more importantly, your tree’s life is shortened! By knowing some pruning basics, you can ensure that you are hiring a professional who knows what they are doing, and will extend the value and life of your landscape.

  1. Carrow, R. N., B. J. Johnson, and R. E. Bums. 1987. Thatch and quality of Tifway bermudagrass turf in relation to fertility and cultivation. Agronomy Journal, 79: 524-530.
  2. Dunn, J. H., D. D. Minner, B. F. Fresenburh, S. S. Bughrara, and C. H. Hohnstrater. 1995. Influence of core aerification, topdressing, and nitrogen on mat, roots, and quality of “Meyer” zoysiagrass. Agronomy Journal, 87: 891-894.
  3. Erusha, K. S., R. C. Shearman, and D. M. Bishop. 1989. Thatch prevention and control. Turfgrass Bulletin, 10(2): 10-11.
  4. Murray, J.J., & Juska, F.V. (1977). Effect of management practices on thatch accumulation, turf quality, and leaf spot damage in common Kentucky bluegrass [Poa pratensis]. Agronomy Journal,(3), 365-369.
  5. Lloyd M. Callahan, William L. Sanders, John M. Parham, Cynthia A. Harper, Lori D. Lester and Ellen R. McDonald.Cultural and chemical controls of thatch and their influence on rootzone nutrients in a bentgrass green.Crop Science, 1998 38: 1: 181-187. doi:10.2135/cropsci1998.0011183X003800010030x

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Rich Guggenheim is a consumer horticulture educator with the University of Idaho in Canyon County and is the program director for the University of Idaho Extension Master Gardener volunteer program. Rich is also working on a Ph.D. in plant pathology. Rich has been an horticulture extension agent for Colorado State University, horticulturalist for Disney Parks, and is the host of the weekly “Avant Gardener” radio program in Boise. He can be reached at richg@uidaho.edu

My New Project — The Plants We Eat

By Jeff Gillman

The logo!

I love stories, and my favorite stories, as you might guess, are true stories about plants. One of the things that I’m best known for here at the UNC Charlotte Botanical Gardens is telling random stories about some odd tidbit or another to students trapped in my classes or visitors locked into garden tours, but recently I found a new way to share my collection of those eclectic plant stories: Podcasting. Not only do I get to talk about all the things that I love to talk about, only those people who really want to hear about them have to listen. It’s a win-win!

Recording the podcast!

From apples and artichokes to digitalis and peyote, our world is full of amazing plants that we interact with on a daily basis. This greenery can sustain us, intoxicate us, cure us of disease, and even kill us.

I have had the opportunity to read about and work with an incredible variety of plants, but the ones that I find most fascinating are those we ingest as food or medicine, and that’s what this podcast is about. From toxic honey made from Rhododendrons to the incredible photosynthetic efficiency of sugar cane and the natural genetic modification of sweet potatoes there are an incredible number of stories that the plants around us have to tell, but if you’re just interested in growing these plants then we have you covered there too. I am doing these podcasts with a friend of mine, Cindy Proctor, who loves to talk about how to grow these plants, so there’s plenty of that in the podcast as well.

Rhododendron from which Mad Honey is made

So to make a long story short, we would love it if you would take the time to listen to our podcast. You can find it on the podcast app on your iPhone or on Sound Cloud, or here at the Botanical Gardens website.

And since we’re new at this we would love it if you would let us know what you think. You can comment on the blog post here, or on the post on Facebook, or feel free to write to me at jgillman@uncc.edu.

Master Gardeners at a crossroads

{Warning. Today’s post is a rant. So I’ve illustrated it with pretty flowers in soothing colors to make it more palatable.)

Hydrangea

Anyone who gardens in the United States will be familiar with Master Gardeners. The Master Gardener program was started by Washington State University in 1971, when Extension agents in the largest urban counties found themselves overwhelmed with questions from the gardening public. These agents proposed training volunteers to help with educational outreach efforts, and with support from the university the first Master Gardener program was born. The history and function of Master Gardeners is further detailed in a couple of articles I co-authored (Chalker-Scott and Collman 2006 and Chalker-Scott and Tinnemore 2009): the more recent article also raises concerns about the decline of programmatic support in Washington state and elsewhere. If you’re a Master Gardener, the repercussions of this should alarm you.

Iris

What makes a successful Master Gardener? According to Sharon Collman, the last surviving founding agent of the WSU program, it begins with this:

  • A commitment to basic and advanced training program;
  • An open-minded approach to continuing education of themselves as well as others;
  • A willingness to provide science-based, unbiased information regardless of personal beliefs. (From Chalker-Scott and Collman, 2006)
    Pink fawn lily

    To be successful, volunteers need high-quality education consistently provided by university discipline experts. And that’s where the model is starting to fail in Washington state. Extension specialists who used to provide training to Master Gardeners in plant pathology, entomology, lawn and turf management, soil sciences, and other important fields have not been replaced by the university when they resign or retire.  More and more training is left to the devices of individual counties, whose Extension funding from WSU has been gutted over the decades. The previous university-centric approach to Master Gardener training has devolved into volunteer-driven county programs with little educational oversight.

Morning glory

While counties should be commended for keeping programming alive in the face of crippling budget cuts, the lack of meaningful curricular oversight by the university means that volunteers often don’t get the most current and relevant information pertaining to the science of gardening. Worse, they may be taken in by popular products and practices with no basis in science. Other volunteers may let their personal beliefs interfere with their pledge to provide objective, science-based information on topics including pesticides, GMOs, and other controversial topics. This undermines the credibility of the county program and ultimately the university who claims these volunteers.

Oregon oxalis

If you are a Master Gardener in Washington state or anywhere else in the U.S., it’s really incumbent upon YOU to insist that your land-grant university live up to its public outreach mission. You DESERVE access to Extension faculty specialists whose primary focus is to educate the gardening public.  The university takes credit for your volunteer hours when they make reports to the state legislature. Make them earn it.

Rose

Don’t waste your time contacting the university – you’ll get nothing but platitudes there. The place for change to start is with your elected state representatives.

Let’s be rational about roots

One of my colleagues alerted me to a blog post on tree myths currently making the rounds on social media. As a myth debunker myself I was particularly intrigued by the last myth “Root Pruning Stimulates Root Branching:”

“When planting a tree’s root ball, It is very tempting to cut back on roots that are circling the ball. It is very often thought that a dense root ball will stimulate new feeder root growth…but that is not the case.

“Don’t worry about encircling roots as they will correct that on a new site.

(Yeah right)

“Most new root growth occurs at the end of existing roots. Root pruning is often done at the nursery to accommodate packaging and to resume growth before the final sale. If you are planting the tree at its final site, it may be best that you gently break up the root ball but never prune root tips.”

Most surprising of all was the statement at the end of the post which cited an Extension publication by Dr. Ed Gilman at the University of Florida.

Let’s straighten this out (pun intended).

First of all, root pruning DOES stimulate new root growth. It’s just like the response you see when you prune the crown of a plant – the buds below the cut become active and develop into new shoots. There are growing points behind the cut ends of roots which act in the same manner.

Young root branching

Second, circling roots will NOT correct themselves after planting. If they are flexible, you can tease them out to radiate from the trunk. If they are woody, you will have the same luck straightening them as you would in straightening a dowel. If anything, it’s going to break. Not bend.

Seriously. You think this root is going to straighten out?

Finally, root elongation (growth) DOES occur at the end of existing roots – IF they are intact. If they’ve been cut, then we’re back to my first point.

This is basic plant physiology. The response of roots to pruning has been known for several decades. So how could the University of Florida publication be so wrong?

Excessively long roots can easily and safely be pruned before planting

I was able to track down the publication “Dispelling Misperceptions About Trees“. It was written in 1991 and has since been archived – meaning that it’s not considered to be a current source of information any longer. But let’s take a look at what it says, especially the underlined portion:

 Root pruning does not stimulate root branching all the way back to the trunk. Roots are often pruned before moving a tree in hopes of creating a denser root ball.However most root growth after root pruning occurs at the end of the root just behind the root pruning cut, not back toward the trunk. Therefore, dig the root ball of a recently root pruned tree several inches beyond the location of the root pruning. Root pruning should be conducted 6 to 10 weeks before moving the tree. Root pruning more than 10 weeks before moving the tree will reduce the advantages of pruning, because regenerated roots will quickly grow outside of the root ball.”

Root pruning when these trees were dug results in many new flexible roots

This says exactly what I stated in my first point: root pruning stimulates new root growth – which is root branching.

Dr. Gilman’s document goes on to say:

“Roots circling around a container do not continue to grow in a circle once the tree is planted in the landscape. Roots frequently circle within the perimeter of a container several times before the tree is planted into the landscape. The portion of the root which grew in the container does not straighten out, but new growth on this root will not continue to circle.”

So yes! You DO need to worry about those circling roots!

Circling roots turned this crape myrtle into a crap myrtle (Courtesy of Roger Duvall)

In 1991 Ed was an assistant professor at UF and went on to write hundreds of Extension publications and research articles during his career. And in 1991 he was well aware of how root pruning affects root growth.

The moral to this story: read your sources carefully and cite them accurately. And if what you read doesn’t jibe with the current state of science, ask questions!