First winter 2026 damage assessment

This has been a strange winter. We hit 33°F a few times in January but never dipped below freezing. I can’t remember the last time that happened, maybe never.

On the other hand, we also had the longest streak of tule fog since 1970 — 22 consecutive days in December, and a few more in January. Nighttime lows and daytime highs were only a few degrees apart in the 42-45°F range. A persistent blanket of moisture clung to everything, with no wind to help dry things off. This unfortunate combination of factors was more than enough to do real damage.

Here’s an echinopsis that sailed through last winter and yet rotted as a result of the lingering wetness and cold:

Rotting from the ground up, even though the soil is loose and well-draining

The rot has progressed too far to rescue this poor thing

Typically, I don’t worry about tender agaves until temperatures get close to freezing. But below is proof that the dreaded black spots can appear even when nighttime lows are in the low 40s.

The first afflicted plant is Agave desmetiana ‘Ivory Star’. It has a smattering of black spots caused by the anthracnose fungus. I’ve since moved it to a sheltered spot on the front porch where it will stay fairly dry.

Agave desmetiana ‘Ivory Star’

Agave desmetiana ‘Ivory Star’ in its new overwintering spot on the front porch

Fungus spots on Agave simplex ‘Snow Devil’. Clearly, the variegated parts are more susceptible than the green parts.

Variegated Agave potatorum like this ‘Eye Scream’ are such wimps, but I like them anyway

The damage on these agaves is cosmetic. They will outgrow it over time.

The Euphorbia lactea ‘Gray Ghost’ in the backyard was not so lucky. The black spots you see in the photo below progressed rapidly, eventually turning the stems into a pile of mush. There was no way to stop the rot. The pot it was in is now empty, and it shall remain empty until spring.

Euphorbia lactea ‘White Ghost’ with cold damage. This cultivar appears to be very sensitive, with damage showing up in the low 40s.

Oddly, the trio of Euphorbia ammak ‘Variegata’ a few feet away escaped unscathed. Not one spot.

Euphorbia ammak ‘Variegata’

More rotting plants that were beyond saving:

Aloe brevifolia

Aloe brevifolia × claviflora

Aloe brevifolia × claviflora cut in half. The rot had already entered the meristem.

Mammillaria plumosa, looking fine from a distance, but total mush in the middle

Even some plants in the greenhouse rotted:

Euphorbia abdelkuri developed quite a fuzz. This species is super tender. I won’t get another one, it’s just not worth it.

Unidentified Stapelia. I’ve lost I don’t know how many stapelias over the years. Another group of plants I won’t touch again.

The next set of plants started to rot, but now the rot seems to have stopped. I know it doesn’t look like it, but there is a chance they will pull through.

Aloe fosteri

Bicolored Aloe ferox

Gasteria excelsa

Even though winter lows have stayed above freezing, we had a string of cold nights between 35°F and 33°F. That was enough to fry the tips of some flowers:

Aloe rubroviolacea

Veltheimia capensis

Other plants I had worried about shrugged off the cold and damp and look as good now as they did in late fall.

Agave titanota × Mangave ‘Bloodspot’, a Nick Deinhart hybrid

Euphorbia horrida ‘Snowflake’ and Agave victoriae-reginae ‘White Rhino’

These golden barrels are in an area that gets relatively little sun in the winter. They’re not tender, but they can rot when it’s wet for an extended period of time, especially in sunless spots.

The most frustrating thing about this winter: There are no lessons to be learned, because the cause of all this was an unfortunate combination of low temperatures, prolonged fog with pervasive dampness, and a complete absence of wind.

If it’s any of these factors on its own, it’s much easier to take protective measures. If it’s frost, throw a frost blanket on sensitive plants. If it’s rain, move potted plants onto the porch or cover in-ground plants that have a hard time dealing with winter wetness.

We still have another six weeks ahead of us when things could turn iffy. If I had to choose between freezing temperatures and extended fog, I’d choose the former. But I hope that neither will rear its ugly head.

I’ll post a final damage assessment when spring is in the air, early March or so.

© Gerhard Bock, 2026. All rights reserved. To receive all new posts by email, please subscribe here.