Gadenin日本語Get the appDamage matters more here than on a food crop
A kale grown for eating can lose a third of its leaf area and still be a perfectly good crop. An ornamental kale cannot, because the whole value of the plant is the appearance of an intact, symmetrical rosette. A single caterpillar working across the colored center for two nights can leave holes that stay visible for the entire winter, since the plant grows too slowly in cold weather to replace or hide them.
That changes the priority completely. The window that matters is late summer and early autumn, while the plant is still growing and while nearly all the chewing pests are still active. Damage done then is what you look at in midwinter. Check the plants twice a week through those weeks, and specifically look into the center and under the leaves rather than glancing at the tops.
| Problem | What you see | What to do |
|---|---|---|
| Caterpillars | Ragged holes, green or brown pellets in the center | Pick off by hand. Net the plants before moths arrive |
| Gray cabbage aphid | Waxy gray colonies packed into the center folds | Squash or wash out early. Whole plant if colonies persist |
| Pigeons | Leaves stripped to the ribs overnight | Netting held clear of the leaves. Nothing else works |
| Slugs and snails | Irregular holes, slime trails, damage worst after rain | Evening patrols. Clear dead leaves and hiding places |
| Flea beetle | Dozens of tiny round shot holes on young leaves | Only harms seedlings. Keep them watered and growing on |
| Crown rot | Soft brown collapse at the center or base | Remove the plant. Improve drainage before replanting |
| Clubroot | Stunted, wilting in sun, swollen distorted roots | Remove and destroy. Do not grow brassicas there for years |
Caterpillars and pigeons: net early or accept the damage
Cabbage white caterpillars and cabbage moth caterpillars are the main threat while the weather is still warm. The eggs are laid on the undersides of leaves, in neat clusters or singly depending on the species, and are far easier to deal with than the caterpillars they become. Turn over a dozen leaves each time you pass and rub off any eggs you find. The caterpillars themselves feed at the growing point, which is exactly where you least want holes, and the dark green or brown pellets of frass sitting in the center folds are usually the first thing you notice.
Netting is the reliable answer and it has to go on before the plants need it, from planting out. Use a fine mesh, and hold it clear of the foliage on hoops. Netting resting on leaves is useless because the moths lay through it and pigeons peck through it. In late autumn and winter, once the moths are gone, the netting is earning its keep against pigeons instead, and in a hard winter pigeons will strip an unprotected ornamental kale to bare ribs in a single day.
Gray cabbage aphid in the center
This one is specific to the cabbage family and it is worse on ornamental kale than on almost anything else, because its favorite site is the tight, sheltered center of a rosette. It forms dense colonies of small gray green insects coated in a mealy white wax, packed into the folds where you cannot easily see or reach them, and it stays active late into the cold season when other aphids have gone.
The wax coating repels water and sprays, so a colony that is well established in the center is genuinely difficult to shift. Catch it early instead. Part the central leaves and look every week from planting out. A small colony can be squashed between finger and thumb or blasted out with a jet of water on a mild day, dried off afterwards. A large one that has already distorted the young central leaves is not worth fighting: the color is spoiled, and the plant will keep on harboring the aphids all winter. Pull it out, bag it and remove it rather than composting it.
Note which plants and which part of the bed had aphid or caterpillar trouble, with dates. Both problems are strongly tied to position, shelter and the timing of the local moth flights, and a couple of seasons of notes will tell you the exact fortnight in which netting has to be on in your garden.
Rots, and cold wet soil
Ornamental kale is thoroughly hardy and frost does not damage it. What damages it is water sitting where it cannot drain, at a time of year when the plant is too cold to grow away from any injury. Gray mold gets in through dying lower leaves left lying against the stem and works upward. Soft brown rot at the very center almost always starts with water that collected in the cup of the rosette and then froze.
The preventive measures are all mechanical. Water at soil level, never over the top, and water in the morning. Pull dead lower leaves off as they go soft rather than leaving them. In containers, raise the pot on feet so it drains freely and never leave it standing in a saucer of water through winter. In heavy ground, plant on a slight mound so the crown sits above the surrounding soil. A plant that has gone soft in the middle will not recover and should be removed before the rot spreads to its neighbors.
Clubroot and where you plant next year
Clubroot is the one problem that outlasts the plant. It is a soil organism that infects the roots of the cabbage family, swelling them into distorted clubs, and the plant above ground is stunted, oddly purple and wilts in sunshine even when the soil is wet. There is no cure for an infected plant, and the spores persist in the ground for many years.
Because ornamental kale is grown for looks it often goes into a bed edge or a container rather than the vegetable plot, which is genuinely useful here. Rotate the position from year to year, never put it where any other brassica grew last season, and if you have found clubroot anywhere in the garden, grow it in containers of fresh compost instead. Lift and destroy any plant with swollen roots, do not compost it, and clean tools and boots afterwards.