Gadenin日本語Get the appTreat it as a brassica, because it is one
Stock belongs to the cabbage family, and that single fact predicts most of its troubles. Anything that attacks cabbages, kale, turnips, radishes, rocket or wallflowers will attack stock, and anything stock leaves behind in the soil will affect the vegetables that follow it. Gardeners who rotate their vegetables carefully and then plant stock into the brassica bed year after year are undoing their own work.
The practical rule is to include stock in your brassica rotation and keep at least three years, preferably four, between brassica crops of any kind on the same ground. Also pull out and remove flowering weeds of the same family, such as shepherd's purse and charlock, which host both club root and flea beetle over winter.
The other family habit worth knowing is that stock hates compacted, acidic, badly drained soil in exactly the way cabbages do. Lime to bring the pH nearer neutral, break up the ground, and add grit if it is heavy. Most of the disease pressure below drops away when the drainage is right.
| Problem | What you see first | When it strikes | What to do |
|---|---|---|---|
| Club root | Wilting in sun, recovering at night, stunted plants | Any time, worst in acid wet soil | Pull and bin, lime the ground, rotate four years, never compost the roots |
| Flea beetle | Pinprick round holes in seedling leaves | Warm dry spells, seedlings only | Row cover the bed, keep the soil damp, grow seedlings on fast |
| Cabbage caterpillars | Ragged holes, green droppings on leaves | Warm months | Net with fine mesh, pick off by hand, check leaf undersides |
| Aphids | Curled tips, sticky leaves, ants running the stems | Mild spells, worst on soft fed growth | Rub off with fingers, hose down, cut the nitrogen |
| Stem rot | Soft dark ring at soil level, sudden collapse | Cold wet ground after planting | No cure, pull it, improve drainage and water less |
| Downy mildew | Yellow blotches above, gray down below | Cool still damp air, crowded plants | Space wider, water at the base in the morning, remove leaves |
| Gray mold in the spike | Browning florets, fuzzy gray growth | Wet weather at flowering | Deadhead promptly, improve air movement, avoid overhead watering |
Club root is the one that stays
Club root is a soil-borne organism that swells the roots into distorted clubs so they cannot take up water. Above ground the plant wilts in the middle of the day, picks up overnight, and stays small. There is no treatment. Once it is in a bed it can persist for many years, so the aim is entirely to avoid introducing it and to slow it down where it already exists.
It arrives most often on bought plants and on soil carried on boots and tools from another garden or an allotment. Raise your own from seed where you can. If you must buy plants, knock one out of its pot and look at the roots before it goes anywhere near your ground.
Where it is already present, it can be lived with. Lime to raise the pH towards 7.0 or a little above, since the organism does far more damage in acid soil. Improve drainage, because it thrives in wet ground. Plant into a generous hole of clean bought compost so the young plant builds a good root system before it meets infected soil. And accept that stock in that bed will always be second best, and grow it in containers instead.
Flea beetle is a seedling problem only
Small dark beetles that jump when disturbed chew shallow round pits and holes through young stock leaves, and in a warm dry spell they can shred a tray of seedlings in a couple of days. On an established plant the same damage is cosmetic and irrelevant; the whole risk window is from emergence until the plants have six or eight true leaves.
The reliable answer is a physical barrier. Cover the seedbed or the freshly planted row with insect mesh or row cover from the day you sow, sealed at the edges with soil, and leave it on until the plants are past the vulnerable size. Beetles cannot fly in, and nothing else is needed.
Without a barrier, the second best approach is to make the seedlings unattractive and get them past the stage fast. The beetles prefer hot, dry, dusty conditions, so keeping the soil surface damp reduces attack noticeably. Watering and feeding to push rapid growth shortens the window. Sowing early, into cool conditions, avoids the worst of the beetles' activity altogether, which is another quiet argument for sowing sooner than feels natural.
Yellow sticky traps laid flat just above the seedlings catch a useful number of beetles as they jump, and more usefully tell you the moment an attack has started.
Rot, mildew and the things caused by watering
More stock is killed by water than by any pest. Stem rot appears as a soft, darkened band at soil level; the plant may look normal until the day it topples. It cannot be saved. It follows cold wet soil, planting too deeply, and mulch heaped against the stem, so plant into raised or grit-improved ground, keep the crown clear, and water thoroughly but infrequently rather than lightly and often.
Downy mildew shows as pale yellow patches on the upper leaf surface with a fine gray-white growth on the underside, and it takes hold in crowded plantings where the leaves stay damp overnight. Space at the recommended distance rather than squeezing plants in, water the soil rather than the foliage, and water in the morning so leaves dry before dark. Remove affected lower leaves as soon as you see them.
Gray mold gets into the flower spike in wet weather, working outward from florets that are already going over. Deadheading promptly and cutting for the house both remove the material it feeds on, which is the main reason a regularly cut bed of stock stays clean while a neglected one turns brown from the middle.
Keeping records that actually help
Write down which bed each batch of stock went into, and the date. Club root and flea beetle are both problems of repetition, and a two-line record of what grew where is what makes a four-year brassica rotation possible when the plants involved are flowers rather than vegetables and are easy to forget about.
Note the first date you saw each problem, not just that it occurred. Flea beetle arriving at the same point in two consecutive springs tells you exactly when the row cover needs to go on. A first sighting of wilting in one particular corner, repeated, tells you where the drainage is bad long before you would work it out any other way.