Response to drought and heat: part 1

One of the biggest surprises of this year’s drought and heat wave was how my alpine bottlebrush (Callistemon pityoides sieberi) suddenly seemed to collapse. According to the tag, it is summer drought tolerant and takes full hot sun all day. Plus, it’s planted literally just feet away from our creek.

Heat and drought damage to bottlebrush
Callistemon pityoides sieberi

Nope, didn’t matter. Not such a happy plant. The damage seemed to happen so suddenly, one day this bottlebrush was green and healthy, the next day yellowish-brownish sickly green. By the time I noticed the color change in mid-August, the damage had been done. I watered it immediately and hoped that would be enough to save it. A few weeks later, most of the older leaves had turned brown, but it does look like the youngest growth is still alive. It’s the only bottlebrush in the yard that suffered damage from the drought.

Brown leaves on the alpine bottle brush
Callistemon pityoides sieberi

Although I am thrilled that it looks like I saved it, it is no longer the nice specimen shrub that it once was. I am hoping to take cuttings this winter and then cut it back to a stump in the Spring of 2022 to rejuvenate it. We’ll see if this works. I hate to lose this plant as it is one of my favorite bottlebrushes.

Next up, some plants out in the deer garden. Someday, I will have to write up a description of each of the different gardens in the yard. But, in the meantime, the most important thing to know is that the deer garden is the unfenced part of the yard where I trial plants to see how much neglect they can take and whether the marauding deer bother them or not. The plants in the deer garden didn’t get watered this year until I started to see drought damage around mid-July. Then, I watered different plants out there sporadically, depending on their needs, maybe six times this summer.

First in the showcase is our dwarf Jerusalem sage (Phlomis fruticosa nana), a normally drought tolerant plant.

Leaf curling on drought stressed Phlomis fruticosa
Phlomis fruticosa nana

Even though the dwarf Jerusalem sages in the rest of the yard look fine, the ones out in the deer garden seem to have suffered. Note the curled leaves. This is a common response in many plants to drought stress. As of October 9th, we have had two decent rains, yet the leaves are still curled up. Definitely still alive, but I am hoping the leaves will return to normal soon. Here is a close-up of the curled leaves.

Leaf curling of drought stressed Phlomis
Phlomis fruticosa nana

My understanding of the leaf curling process is that it is supposed to enclose and protect the stomata, which are the microscopic pores on the leaves where the plant “breathes” by taking in carbon dioxide and releasing water vapor and oxygen. When the plant curls its leaves, it is essentially reducing the amount of water that it “breathes” out, sort of like how a scarf or face mask traps the moisture in our breath. Curled leaves = less moisture loss. Now the weird thing to me is that I thought most stomata were generally located on the bottom sides of the leaves, not the top. So, the leaves should curl downward to protect the stomata that occur down there. However, if we look at the pictures, the leaves have curled up, which would expose all of the stomata on the bottom of the leaf to more hot sun and dry air, thus potentially causing the plant to dry out more quickly. Odd. Obviously something in my train of logic is wrong and I hope to take a look more deeply into this subject for a winter blog post.

But, onwards and upwards with the drought and heat report. Next up, but totally not a shocker, is that my peonies hated, absolutely hated, the drought and heat this summer. This one (maybe Paeonia lactiflora ‘Lian Tai’) collapsed early and never regained its composure.

Collapsed peony from drought stress
Paeonia lactiflora cultivar

Take a look at how burnt the stems are down where they grew out from the soil. The sun just cooked them during that horribly hot weekend in June. Temperatures on June 26th-28th were 105, 113, and 117°F (40.5, 45, and 47°C)! Our normal summer temperatures in June are typically in the mid 70s (around 24°C), so this was completely abnormally, devilishly hot. But, enough water still got through the burnt stems to provide life support (leaf support?) to the leaves up top. I am expecting a full recovery next year.

Base of a peony stem burnt by heat
Paeonia lactiflora cultivar

My tree peony (Paeonia delavayi) also didn’t like the heat or the drought. The leaves are permanently wilted and scorched, but I also expect that this plant will recover next year. The cypress hebe (Veronica cupressoides) to the left of it was fine though, and didn’t care one bit about either the heat or drought.

Drought stressed Delavay's tree peony
Paeonia delavayi

Another plant that didn’t seem to mind either the heat or the drought was this lamb’s ears (Stachys byzantina). I didn’t water it once and it still looks fine. I do, however, dislike the yellow spots that develop on the older leaves every summer (cycle through the slide show by clicking on the arrows). I’ve got a strong suspicion that those spots are from insect feeding, perhaps from the nymphs of this western boxelder bug (Boisea rubrolineata)?


The purple flowers in the background of the first picture are from a Russian sage (Salvia yangii, aka Perovskia atriplicifolia), which also didn’t get watered and did fine.

I had another unpleasant surprise when my groundcover form of the alpine tea-tree (Leptospermum rupestre ‘Prostrate’) started to turn yellow and dry up in mid-July. I watered immediately and saved it. Yay! I ended up watering it three or four times this year. Another, older specimen in the rock garden did fine, so the drought stress was probably a function of this plant being younger and having a smaller root system.

Minor drought stress on
Leptospermum rupestre 'low form'

Close-up of the drought damage. I’ll either prune this out later, or it will naturally disintegrate over the winter and disappear. Again, this is a very low-input part of the yard. I want plants that are low maintenance, drought tolerant, near deer proof, and look good despite neglect. Primping and pruning are not a high priority in the deer garden.

Dying leaves on a drought stressed alpine tea tree
Leptospermum rupestre 'low form'

That’s it for now. I will have upcoming installments of how my plants fared in the heat and drought coming up later this fall.

By the way, the perfectionist in me was torn between capitalizing the names of the seasons (Spring, Summer, Fall, Winter) or leaving them in lower case. I learned to capitalize season names in elementary school, but now most people don’t capitalize them anymore. Ah, the dilemmas of a perfectionist. I’ve just decided it doesn’t matter and I like the way they look better in lowercase. Just a peak into the meaningless chatter of my brain…Fun, fun.

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