Are your succulents turning black? Are they gushy and soft when you touch them? The small accent color plants from warm dry climates slow down with the shortening of days into winter. They stop growing and therefore need no moisture besides what their bodies already hold. Yet water is continually applied, be it by rain or automatic sprinklers or a diligent overwater-er. This demonstrates why the small succulents rot out over winter, not necessarily from frost but lack of light and too much moisture.
When moisture accumulation meets morning frost, there’s a perfect environment to start rot. This is the enemy of all succulents. Their water-holding interior tissues are sterile, protected by a hard outer skin that prevents moisture loss. When this outer skin gets damaged by frost, or any other cause, fungus and bacteria set in. They need evenly moist conditions to proliferate before the wound dries out and heals over.
Once you find rot on a succulent, be it a huge agave or a tiny lithops, you’re already at a disadvantage. The rotting organisms are already inside doing their worst to spread throughout the entire plant body. They won’t stop until the whole plant melts down into goo.
There is a remedy, if you have a strong hand and good eye. First observe the rot, which is usually a yellow or brown spot. It often begins at the soil line where too much moisture is in contact with the green skin of the plant, which is much like earth-to-wood contact rotting wood posts. Rotting can also be stimulated by tiny skin breaks during transplanting, particularly if it’s a thin skinned species.
Use a fingertip to lightly press the rot to see how soft it is. Sometimes sunburn looks like rot but is just skin discoloring. Softness is the clue. If rot is there, it will feel softer under gentle fingertip pressure than the surrounding unaffected skin. A little softness means the rot is localized. By the time it’s so soft your finger goes right through the skin, it may be history.
Succulents are resilient, so once you assess where the rot is by sight and feel, strategize how to surgically remove it. Just like cancer, you must remove all the rot, especially residual tentacles extending further into normal tissue. These inevitably contain pathogens that will resurface.
It won’t be pretty after you’ve cleaned out the plant, but don’t give up. Succulents have truly amazing healing powers. Place the plant in the shade for a few days to help the skin callus into a new outer skin to hold the moisture. If you had to remove part or all the roots, treat them the same before reinserting into media so root initials will develop quickly. If you can’t salvage the plant itself, consider segmenting the healthy tissue and rooting it in moist clean sand.
Every encounter of ailing succulent plants is almost always a rot problem — they’re really trouble-free as a group. It can lurk in the center of an old Beaucarnea caudex only to surface after a rainy period. In dry desert climates rot rarely occurs in succulents except when associated with irrigation.
The best way to protect your succulents from rot is to protect them from frost. When frost nips at the tips of your Euphorbia, it’s an injury that is exacerbated into rot by rain at just the right time. Maybe it’s too high to notice until the whole top end discolors. So many homes feature large and very expensive specimen succulents that may be borderline tolerant of the climate. Keep Plankets or a bed sheet on hand for those cold snaps this winter. For narrow tall cactus such as fence post, slide a recycled plastic foam coffee cup over the top to protect from tip burn.
The regions where most of these plants come from are high UV in the winter, so overcast days put them into a funk, then rot sets in. Protect what you can and let the others go because they’re probably going to rot. Then come spring, you may be surprised at what survives.
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Maureen Gilmer is an author, horticulturist and landscape designer. Learn more at www.MoPlants.com
