It kicked off in July with a never-ending tropical stretch—lots of heat, humidity, and muggy warm nights. August turned up the warmth and stickiness even more, while the ocean stayed an unusual 70°F plus for weeks. We were hoping September would cool things down, but instead we got a surprise late-season blast: an unusual six-day run of 90°F-plus weather (topping out at 105°F) that broke old records. On the bright side, it was a “dry heat” with less humidity.
By the second week of October, the humidity was back—and so was Tropical Storm Rachel! While the expected high winds didn’t show up, most of the county finally got its first real rain since April. Hopefully, this helped lower the risk of big wildfires. It’s pretty normal for San Diego to stay dry this long (and sometimes even longer), but this is only the second time in 100 we’ve seen a tropical storm warning with the first rain. Who knows what this record El Niño year has in store for us?
But I’m supposed to writing about plants…
You’ve probably noticed many of your plants showing stress from this extended hot weather – everything from leaf burn, wilting, yellowing to death. Even plants that are supposed to be adapted to hot and dry weather are showing signs of heat stress.
Regarding the yellowing of leaves, it is caused by the breakdown of chlorophyll which impacts a plant’s ability to photosynthesize. According to google here are 3 main reasons why this occurs in hot weather:
- Chlorophyll Breakdown: Excessive heat (often temperatures above 90°F / 32°C for many species) damages plant cell membranes and degrades existing chlorophyll faster than the plant can rebuild it.
- Unmasking Other Pigments: As the green chlorophyll fades, underlying yellow or orange pigments (carotenoids) that were previously masked become visible.
- Secondary Heat-Stress Factors: High heat often accelerates soil drying and evapotranspiration. If the plant cannot draw up water fast enough to keep pace with the heat, roots experience stress or dehydration, which further halts nutrient transport and triggers yellowing or leaf scorch.
I’m not exactly sure which plants where affected by which of these, but I expect maybe a little to a lot.
Plants with yellowed leaves:
- Agave victoria-reginae: The center of many of the tighter agaves turned yellow. It should be dark green. It will likely recover.
- Kalanchoe thyrsiflora: While it looks fine, it should be a deeper green with the yellow tint. Many of the older leaves dried up.
- Bromeliads: Many of the bromeliads lost their color and turned pale yellow with leaf burn on the tips. The one in the photo is usually a bright red with green leaves at the base.
This Euphorbia and two cactus that were exposed to direct hot sun all took on yellow tint. The Euphorbia also has some brown spots that will never turn green.
A couple of aloes were just in spots that got too hot. The first is by a south-facing wall that reflected and held in the heat. The second is the giant tree aloe that was originally planted in front of the house, but fell over in the big, wet, and windy New Year’s Eve storm. We weren’t able to move it with the roots and planted it as a giant cutting. It was just starting to show signs of perhaps some new growth when the heat wave hit. I wrote a blog about the process of relocating it: https://mylifewithplants.com/2026/01/15/new-years-surprise/ Hopefully both aloes will survive.
Plants with leaf burn and desiccated leaves:
Hibbertia scandens: This vine, native to eastern Australia has large, has bright yellow flowers most of the year, as shown in the photo on the right. Many of its leaves have burned. It is now dropping all of these, but they will quickly be replaced. No permanent harm has been done other than a lot of cleanup.
These are my neighbor across the street’s 50-foot-tall Ginkgo trees. They’ve been there over 20 years. Unfortunately, unlike most Ginkgos, these never have yellow fall foliage. Instead, by the time the leaves start to fall, they are almost entirely leaf-burn brown. But this year, the burn is much earlier and worse. They are planted next to a lawn and get a lot of water, probably too much water every day. I’m not sure if it is the cultivar or the water, but they never show any yellow leaves. Ones planted a few miles away in Presidio Park usually turn a brilliant yellow in autumn.
Edema in Succulents:
Succulent edema is a physiological condition caused by water retention, where roots take up water faster than the leaves can release it through transpiration, causing internal cell walls to burst. It shows up most often in well-watered succulents.
For me, it is a problem with many Agaves. Especially ones that are too wet and in the fall when the sun angle changes and they started getting direct sun on the sides that were in shade during the summer.
These 3 agaves all had cells in their leaves burst. The first is “Joe Hoak” in a pot right by the front gate. Reflected heat from the wall behind it really cooked it. The second was recently planted in the ground and is showing both yellowing and dead spots on the leaves. It was in a slightly shady spot before planting and this spot it is in full sun most of the day. The third is one of 3 potted agaves sitting on a wall. It’s been in full sun all summer and gets good airflow, but the 100-degree heat was just too much for it.
I I planted the 3 agaves in pots on the hillside and replaced them with other agaves I had that weren’t burned. I planted them with other agaves in a bit of shade where they can send out new leaves and recover.
Many succulents keep their stomata closed during the hot daytime and opening them at night when temperatures are cool and humidity loss is minimal. This seems to be the cause of burning on the sides of cacti that don’t have dense needles for self-shading. But it also occurs on many crassulas.
Dead Plants
Some plants just give up all together and die. The plant on the left below is a dead Leucospermum. Unfortunately, just before the hottest weather, I cut back the Leucodendron that was shading it. That exposed it to much more sun and it died quickly. The Banksia right next to it was unphased by the heat.
The Agave pup looks like it might be dead, but hoping it will recover. Oddly the parent plant is fine.
Things that weren’t much affected by the heat
Many tropical plants in the shade and with adequate water seemed to flourish in the heat and humidity— plants like caladiums, begonias, and many bromeliads.
The potted caladiums were a bit of a surprise. I had always thought that our cool nights and consequently cool soil made it difficult, if not impossible, to grow them in San Diego. On a whim, I bought one last year, and it did great and didn’t go dormant until late November. So I tried a few more this year. They really loved the heat and humidity and performed beautifully.
Signs of Fall
The good news is there are some signs of fall. A few fall blooms that still manage to bloom on schedule.
But the best surprise was the rains from Tropical Storm Rachel that gave most of San Diego a good soaking overnight on Oct. 10/11. I measured about 1.75 inches at our house.
What I did during the heat – Or how I spent my summer vacation
I also did a few other thing during the heat. We escaped to Alaska in August.
Here’ my blog about the trip: https://mylifewithplants.com/2026/09/30/idaho-alaska/
And I completed a long planned project that took me 23 years to complete.
Installed a tile mosaic sun in an arch in the Casita area using leftover tile scraps: https://mylifewithplants.com/2026/09/30/here-comes-the-sun/