Gadenin日本語Get the appWhat a blown sprout actually tells you
A good sprout is a tight bud, hard when you squeeze it, with leaves wrapped so closely you cannot see between them. A blown sprout has opened out into a small loose cabbage with visible gaps, and it will not tighten again. Once a sprout has blown, that sprout is finished, though you can still eat it and the ones above it may yet be fine.
Blowing is not a disease and it is not bad luck. It has three causes and each of them is something you did or did not do months earlier. Diagnosing which one applies to your plants is the whole of sprout growing.
| Cause | What you see | The fix, applied next season |
|---|---|---|
| Loose or unsettled ground | The whole plant leans, sprouts open from the bottom up | Settle the bed three weeks before planting and tread hard |
| Wind rock | A funnel-shaped gap in the soil at the base of the stem | Stake at midsummer, before the plant gets top heavy |
| Too much nitrogen, applied late | Huge dark leaves, soft open sprouts, weak stem | Feed in early summer only, then stop |
| Warm autumn weather | Sprouts stay loose and leafy on an otherwise good plant | Little you can do; pick earlier and smaller |
| Plants too close together | Small sprouts, thin stems, only the top of the stem is worth picking | Space 24-30 inches (60-75 cm) apart |
If only the bottom four or five sprouts have blown and the rest of the stem is tight, that is normal and not a fault. The lowest sprouts form first and often open before you get to them, which is why picking from the bottom up matters.
Staking, and when to do it
By late summer the plant is carrying a heavy head of leaves three feet or more above the ground on a single stem. Every gust levers that stem back and forth, and the movement opens a cone-shaped hole in the soil around the base. Rain fills the hole, the roots sit in water, the plant leans further, and the sprouts open.
Stake before this starts rather than after. The right moment is when the plant reaches about knee height, usually mid to late summer. Staking a plant that has already begun to lean means you are trying to hold up something whose root plate is already broken.
- Drive a cane in early Use a stout cane or stake four to five feet (120-150 cm) long, driven at least a foot (30 cm) into the soil, placed a few inches from the stem so you do not go through the root ball.
- Tie loosely in two places Tie with soft string in a figure of eight, once low down and once near the top of the current growth. The stem still thickens considerably, so leave slack and check the ties again in autumn.
- Earth up the base Draw four to six inches (10-15 cm) of soil up around the base of the stem. This buries part of the stem, encourages more roots, and closes any hole that has already formed.
- Re-firm after autumn gales After any storm, walk the row and tread the soil around each stem again. This takes two minutes and saves the last third of the crop.
Feeding: early and generous, then nothing
Sprouts are hungry plants, but the timing of the feed decides whether that hunger turns into a tall leafy plant or into tight buttons. Nitrogen builds leaf. You want plenty of leaf built early, because the leaves are the factory that fills the sprouts, and then you want that nitrogen to run out before the buds start closing.
Give a balanced feed about three to four weeks after planting and again a month later, then stop nitrogen entirely by late summer. A high potash feed in late summer is useful and will not cause blowing. Fresh manure dug in shortly before planting is the classic mistake: it keeps releasing nitrogen into autumn and gives you a magnificent plant covered in loose sprouts.
| Timing | Feed | Effect |
|---|---|---|
| At planting | Nothing beyond compost dug in earlier | Encourages roots to go looking for food |
| Three to four weeks after planting | Balanced general feed | Builds the leaf canopy that fills the sprouts |
| Midsummer | Second balanced feed, or a nitrogen top dressing | Carries the plant to full height |
| Late summer onward | Potash only, or nothing | Firms the buds; nitrogen now causes blowing |
If you inherit a plant that is already all soft leaf and loose sprouts, stop feeding, remove the yellowing lower leaves to get air in, and accept a smaller but firmer crop from the upper half of the stem.
Water, and where the water goes
Sprouts need steady moisture through the summer, when the plant is building its frame, more than they need it in autumn. A plant that runs dry in midsummer stays short, and a short stem carries fewer sprouts, which is a loss you cannot recover.
Water heavily and infrequently rather than lightly and often: a thorough soak once or twice a week in dry weather, delivered at the base, is worth far more than a daily sprinkle over the leaves. In autumn, ease off. Wet soil and cool weather combine to loosen the plant and encourage rots in the lower sprouts.
What to write down this season
Sprouts give you one attempt a year, and the mistakes take eight months to show, so memory is not enough. Keep a short record and next year's decisions make themselves.
Note the date you planted out, the spacing you used, the date and type of each feed, the date you staked, and the date you first picked a sprout that was genuinely tight. Then note how far up the stem the blown sprouts went. If the blowing started low, the problem was the ground or the wind; if it started high, it was late nitrogen or warm weather. That one comparison is worth more than any amount of general advice.