Aloe Vera Problems: Mushy Leaves, Rot, Mealybugs and Scale

The short list of things that go wrong

Aloe has remarkably few problems, and the majority of them are caused by the grower rather than by anything that arrives from outside. Speed of diagnosis matters more here than with most plants: rot can take a healthy-looking aloe in under a week, while everything else on this list moves slowly enough that a few days of thinking costs nothing.

Before anything else, push a finger into the compost. Damp compost and dry compost point at completely opposite answers, and treating one as the other is how a recoverable plant is lost.

Root rot: what to do the day you see it

Root rot is not something the plant catches. It is what happens when roots sit in wet compost with no air, and cold makes it far worse, which is why most losses happen between autumn and early spring rather than in summer.

What you notice is a leaf that has gone soft and slightly see-through at the very base, gone brown or yellow-brown there, and that comes away in your hand when touched. By the time that is visible the damage is already in the stem, so the plant needs lifting the same day rather than at the weekend.

1. Pull off every soft leaf Take each affected leaf near its base and pull it straight off. Smell the base as it comes away: a sour, sewage-like smell confirms rot rather than ordinary ageing of an outer leaf.
2. Lift the whole plant out and bare the roots Tip it out and crumble all the compost off. Healthy roots are firm, thick and pale. Rotted ones are brown or black, hollow, and slide apart between finger and thumb.
3. Cut back to firm white tissue With a sterilized blade, remove every soft root, then slice up through the base of the stem until the cut face is uniformly white and firm. Any brown streak left in it will carry on rotting after replanting.
4. Dry the plant bare for three to five days Lay it on newspaper in bright shade with air moving until the cut faces are hard and corky. This cannot be shortened, and it is the step people skip.
5. Replant dry into fresh gritty potting mix Use a small pot and fresh cactus mix. Never reuse the old compost, and wash the pot before it goes back into service.
6. No water for ten days Leave it completely dry, then water once, thoroughly, and go back to long intervals. Expect the plant to sit still for a month before it does anything.

If the rot has reached the center of the rosette rather than just the outer leaves, the plant will not recover. Cut off any healthy pups at the base, treat them as cuttings, and discard the parent.

Mealybugs, scale and aloe mite

Only a handful of insects bother an aloe indoors, and all of them hide. Wiping the leaves with a dry cloth every few weeks doubles as an inspection, and it is how most people catch an infestation while it is still on one or two leaves.

Aloe mite is the exception here, because there is no treatment. This microscopic mite makes the plant grow lumpy, warty tissue, usually under leaves or along a flower stem. Cutting well into clean tissue sometimes holds it back, but an infested plant should be kept away from other aloes and is usually best discarded.

Cold damage and sunburn: the two that look alarming and are not urgent

Cold damage is unmistakable once you have seen it. A soft, water-soaked, almost transparent patch appears on a leaf a day or two after a cold night, and over the following fortnight it dries into a papery brown scar. That leaf will never look right again, but the plant itself is usually fine if you move it somewhere warmer and stop watering.

Sunburn is the same story from the opposite direction: a plant moved suddenly into full sun bleaches to white or pale straw on the side facing it, sometimes within one afternoon. The marks are permanent and the plant survives. Neither needs cutting, and cutting in a panic loses leaves you could have kept.

1. Move the plant, then wait a fortnight Get a cold-damaged plant above 50F (10C) and stop watering. Get a scorched plant back into bright shade. Then leave both alone for two weeks and see what dries out and what stays soft.
2. Remove a leaf only if the damage reaches the base Damage in the middle or at the tip of a leaf is cosmetic and the leaf still works. Damage running into the leaf base, or a patch still soft and wet after a week, will turn into rot: pull that leaf off cleanly.
3. Reintroduce sun gradually afterwards A scorched plant has lost its acclimatisation. Give it two or three weeks in bright shade, then a couple of hours of morning sun, before returning it to a full sun position.

Red or bronze coloring along the leaf edges of a plant in strong light or cool nights is not damage. It is pigment the plant produces as a sunscreen, and it usually indicates a plant growing hard and well.

When a plant is past saving

Knowing when to stop saves weeks spent nursing something that will not come back. The test is straightforward: is there any firm, white, undamaged stem left with at least one healthy leaf attached?

If there is, cut everything else away, dry it and treat it as a fresh cutting. If not, the parent is finished, but any pup with its own roots can be saved, so you rarely lose the line entirely.

What to write down

Note the date of the last watering before any soft leaf appeared, the room the plant was standing in, and the date you first saw the symptom. Aloe problems repeat on an annual cycle, so a few lines turn a recurring loss into something you can head off.

After a single year the pattern is usually obvious. Rot almost always follows a full watering given as the weather turned cold, and mealybugs almost always appear a few weeks after plants come in from outside. Both are easy to avoid with a date in front of you, and impossible to avoid from memory.