Gadenin日本語Get the appMost problems are cultural before they are biological
A cyclamen in a cool, bright, airy place, watered from below, with dead material twisted out weekly, is remarkably trouble free. The pests and diseases below almost all take hold on a plant that is already stressed by warmth or by damp still air in a crowded crown. Before reaching for any treatment, check the position and the watering, because a treatment applied to a plant left in the same wrong place simply buys a few weeks.
The one structural weakness of the plant is the crown itself. Dozens of soft stems emerging from one point, packed tightly, at the top of a tuber, in a cool moist pot, is close to ideal conditions for fungal rot. That is why almost every serious cyclamen disease starts in the same square inch, and why weekly clearing of dead stalks is the most effective preventive measure there is.
Catch things early by looking into the plant, not at it. Part the leaves once a week and look down at the tuber surface. Everything below is visible there before it is visible from above.
Gray mold and crown rot: the two that kill
Gray mold shows as fuzzy gray growth on faded petals, fallen leaf fragments and the base of stalks, and it spreads from dead tissue into living tissue. It needs damp still air, which is exactly what a plant standing in a foil wrap, packed against its neighbors, or misted regularly provides. Remove every affected part by twisting it out, clear all debris off the compost surface, space the plants out, and increase air movement. Do not mist. Cutting stems rather than twisting them is a direct invitation to it.
Crown and tuber rot is the more sudden of the two. Stalk bases go water soaked and translucent, then brown, and a whole side of the plant collapses over a couple of days with a sour smell. The usual cause is water poured into the crown, a tuber buried too deep so the crown sits below the compost line, or a pot left standing in water. Stop watering immediately, strip out every soft stalk, and move the plant somewhere cool and airy. If the tuber is still hard the plant may rebuild from the undamaged side; if it yields to a thumb it is finished and should be thrown out rather than nursed.
Neither is worth chemical treatment on a houseplant. Both respond to air, space and dryness at the crown, and both come straight back if the conditions that caused them are unchanged.
A plant that has lost half its crown to rot but still has a firm tuber is worth keeping. Let the compost dry right out, remove all damaged tissue, keep it cool and barely damp, and treat the rest of the season as an early dormancy. It will often come back normally the following autumn.
The pests, and which ones matter
Three pests turn up on cyclamen with any regularity. They differ enormously in how serious they are: aphids are a nuisance, vine weevil is fatal but visible in time if you look, and cyclamen mite is the one that quietly ruins a plant while you are looking for something bigger.
| Pest | What you see | Seriousness | What to do |
|---|---|---|---|
| Aphids | Green or gray clusters on flower stems and young leaf stalks, sticky leaves below | Low | Wipe off or rinse the stems under a tap holding the pot sideways so nothing enters the crown |
| Cyclamen mite | New leaves puckered, curled and stunted, flower buds distorted or failing to open; mites too small to see | High | No practical home cure; isolate at once and usually discard, as it spreads to other plants |
| Vine weevil grubs | Plant wilts and does not respond to watering; tuber loose in the pot, roots eaten away | Fatal | Tip out the pot, pick out the white C shaped grubs, repot in fresh compost if the tuber is firm |
| Adult vine weevils | Notched semicircular bites out of leaf margins, active at night | Low directly, high as a warning | Notching means eggs are being laid; check the compost for grubs before autumn |
| Fungus gnats | Small dark flies running over the compost surface | Very low | A sign the compost is being kept too wet; let it dry more between waterings |
Distortion, yellowing and other symptoms that are not pests
Distorted new growth is the symptom worth taking seriously, because cyclamen mite is invisible without magnification and is diagnosed entirely from the damage. If new leaves emerge puckered and cupped with rough thickened surfaces, buds abort or open lopsided, and the problem is confined to the newest growth while older leaves look normal, treat it as mite. Separate the plant from every other plant in the house immediately. There is no reliable domestic treatment and infested plants are usually best destroyed.
Yellowing leaves are far more often not a disease. Even yellowing from the oldest outer leaves inward in spring is dormancy. Yellowing across the whole plant with soft growth in midwinter is heat. Yellowing with a heavy wet pot is overwatering and the beginning of root damage. Yellowing with a bone dry light pot is drought. Check the pot weight and the room temperature before assuming anything is attacking the plant.
Leaf edges going brown and crisp while the plant is otherwise fine is scorch from direct sun through glass or dry heat from a radiator, not disease. Flowers that open and then turn papery and brown within a day or two are heat as well. In both cases move the plant somewhere colder and the next flush is normal.
Knowing when to give up, and what to note
Cyclamen are worth saving when the tuber is firm, because the tuber is the plant and leaves are replaceable. Press it with a thumb. Hard means keep going, whatever the top of the plant looks like: dry it off, clear the damage, keep it cool, and wait for the next season. Soft, hollow or foul smelling means the plant is gone, and keeping it only risks spreading rot spores or mite to healthy plants nearby.
The one situation where a firm tuber is still not worth keeping is confirmed cyclamen mite, because it moves onto other houseplants readily and is close to impossible to clear at home. Isolation and disposal is the right decision, unpleasant as it is.
Record what went wrong and where the plant was standing when it did. Note the date you first saw the symptom, the room, and the watering method you had been using. Problems on cyclamen repeat themselves in the same positions year after year, so a note saying that the plants on one particular shelf always get gray mold in midwinter is a note that saves the next two plants you buy.