Extremes

Extremes

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.

Saving for the Future: Seed Saving Tricks and Tips

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 was 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.

Making your landscape fire resistant during wildfire season

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.

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.