Gadenin日本語Get the appWhat actually goes wrong
Crassula is a tough plant with a short list of problems, which makes diagnosis unusually straightforward. Work down from the compost, since more than half of what looks like a pest or a disease turns out to be too much water.
Check the plant properly once a month, and do it when you clean the leaves. Tip the pot slightly, look at the drainage holes, run a finger round the base of the trunk, and look into the joints where the leaves meet the stems. That inspection takes a minute and catches nearly everything early.
| Problem | First sign | Where to look | Urgency |
|---|---|---|---|
| Mealybugs | White cottony specks in the leaf joints | Leaf axils, stem forks, the underside of the root ball | Deal with it this week |
| Root and stem rot | Soft leaves dropping from damp compost | The trunk at soil level, and the roots | Same day |
| Scale insects | Small brown limpet like bumps on stems | Older woody stems and leaf undersides | Within a fortnight |
| Spider mites | Fine stippling and faint webbing at shoot tips | New growth in hot dry conditions | Within a fortnight |
| Powdery white leaf spots | Round pale marks that do not rub off | Leaf surfaces after cold damp spells | Cosmetic, act on airflow |
| Sunburn | Bleached or brown dry patches on the sun side | Leaves facing the window or the sky | Move it, but the damage is done |
Mealybugs, the one pest you will meet
Mealybugs look like tiny scraps of cotton wool tucked into the angle between a leaf and the stem, and they hide in exactly the places you do not look. They breed slowly enough that a plant checked monthly never gets a serious infestation, and fast enough that one ignored for a season will be covered.
- Dab each one with alcohol on a cotton bud Isopropyl alcohol on a cotton bud kills a mealybug on contact and dissolves its waxy coat. Work through every leaf joint and stem fork. On a small plant this is the whole treatment.
- Check the roots as well Root mealybugs live in the compost and look like white powder on the root ball. If a plant keeps declining with no pests visible above the compost, tip it out and look.
- Isolate the plant and repeat weekly Move it away from other plants and repeat the alcohol treatment every seven days for three weeks. That covers the eggs that hatch after the first pass.
- Repot if the roots were infested Wash the roots clean, discard all the old compost, and repot into fresh gritty mix in a washed pot. Reusing that compost simply reinfests the plant.
Do not spray a jade plant all over with oil based products in strong sun. The leaves hold the film, the sun magnifies through it, and you can scorch far more leaf than the pest would have damaged. Spot treatment is both safer and more effective here.
Root rot, the one that kills
Rot is the only common problem on a jade plant that ends in a dead plant, and it moves fast once it reaches the trunk. The pattern is unmistakable: compost that has been damp for a week or more, lower leaves going soft and yellow rather than wrinkled, and a trunk base that gives slightly under a finger.
- Get it out of the wet compost immediately Do not wait to see if it improves. Tip the plant out, shake off everything wet, and look at the roots in daylight.
- Cut back to clean tissue Remove every black or hollow root. Slice across the trunk if the base looks discolored and keep going up in half inch steps until the cut face is pale and clean throughout.
- Save the top as a cutting If the rot has gone too far up the trunk, take the healthy top as a cutting, dry it for a week, and start again. This rescues most badly rotted plants.
- Dry, repot small, and wait Air dry the cut surfaces for three to seven days, repot into dry gritty potting mix in the smallest pot that fits, and give no water for a week.
Symptoms that are not a disease at all
A good half of what gets reported as a problem on a jade plant is either normal ageing or a response to a change in conditions. Knowing which is which saves you from treating a healthy plant.
| What you see | What it really is | Response |
|---|---|---|
| Plump leaves dropping after a move or a repot | Light adjustment, not disease | Stop watering and wait for new tip growth |
| One or two lowest leaves yellowing each month | Normal ageing on a growing plant | Pick them off and do nothing else |
| Leaf edges turning deep red | Sun, cold or drought stress color | Nothing. Many growers aim for it |
| Growth stopped in high summer heat | Heat pause, normal for the species | Water less, no feed, wait for cooler weather |
| Corky brown patches on old stems | The trunk becoming woody with age | Nothing. This is the bark you want |
| Fine surface wrinkles on the leaves | Thirst, if the compost is bone dry | One thorough watering restores them in days |
Keeping a record that pays off
Write down the date you first see anything unusual, what the compost was like at the time, and where the plant was standing. Pests and rot both recur in the same season and often on the same plant, and a note saying that mealybugs appeared in the leaf joints after bringing the plant in from outdoors two autumns running tells you exactly when to inspect this year.
The other thing worth recording is what you did and whether it worked. Three weekly alcohol treatments that cleared an infestation, or a cutting taken from a rotted plant that rooted successfully, are the notes you will actually reread.