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How to Grow Brussels Sprouts: The Long Season Explained

Brussels sprouts need 80 to 130 days, firm ground and frost to taste right. Sowing dates, why sprouts blow open, and when to stop feeding.

By Zakaria 5 min read Save to Pinterest — opens Pinterest in a new tab
Sprouts forming in the leaf axils up a brussels sprout stem, with pale pink-tinged leaf stalks
Photo: Tony Alter from Newport News, USA, CC BY 2.0, via Wikimedia Commons
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The longest season of any common vegetable — 80 to 130 days — and it ends in the cold on purpose. Sprouts picked before a frost taste harsh; the same plant in November tastes sweet.

Timing

When to sow where
RegionSowTransplantHarvest
Northern US / UKMid–late spring indoorsEarly summerOct–Dec
Zones 8–10Late summerEarly autumnWinter
Short-season areasEarly spring indoorsLate springSept–Oct

The rule is that sprouts should form in cool weather. Ones that mature in summer heat are loose, bitter and disappointing, which is the single most common reason a first attempt fails.

Working it out: find your first frost date, subtract the days-to-maturity on the packet, then subtract another two to three weeks for raising the transplants. That is your sowing date.

Sowing and planting out

  1. Sow indoors ½ inch deep in modules, or in a nursery bed outdoors
  2. Germination takes 5 to 10 days at around 70°F
  3. Grow on to 4 to 6 inches with 4 or 5 true leaves — about 4 to 6 weeks
  4. Harden off over a week before planting out
  5. Space 24 to 30 inches apart, in rows 30 inches apart. They get big, and crowding costs you sprout size
  6. Plant deeply, up to the lowest leaves — this buries some stem and steadies the plant
  7. Firm hard. Tread the soil down around each plant with your heel

Firm ground is the point most guides skip

Brussels sprouts are unusual in genuinely wanting compacted soil. On loose, freshly dug or heavily composted ground the plant rocks, and a rocking plant produces open leafy rosettes instead of tight buttons.

Tread the bed down before planting, tread each plant in, and firm again after any windy spell. If you have just double-dug a bed, plant something else in it and put the sprouts somewhere that has settled.

Soil and feeding

Conditions
SunFull — 6+ hours
SoilFirm, fertile, moisture-retentive, well drained
pH6.5–7.0. Lime acid soil — this is clubroot prevention
WaterSteady and deep. Irregular watering gives loose sprouts
FeedBalanced at planting, nitrogen stopped by late summer
MulchYes, but keep it off the stem base

Nitrogen timing matters more than nitrogen amount. Feeding into early autumn gives a large leafy plant carrying soft, open sprouts that will not store. A balanced feed early, then potassium-leaning or nothing from late summer, is what produces tight buttons.

Through the season

  • Stake with a cane once plants reach a foot or so. Autumn wind topples them and the rocking ruins the crop
  • Earth up soil around the base for extra support
  • Remove yellowing lower leaves as you go — better airflow, fewer aphid hideouts
  • Do not remove healthy leaves. The plant feeds the sprouts from them; stripping it to “let light in” reduces the crop
  • Water deeply in dry spells. Fluctuating moisture is a direct cause of blown sprouts
  • Top the plant in early autumn — pinch out the growing tip — if you want an earlier, more even crop. In a long mild autumn, leave it and pick over several weeks instead

Problems

What goes wrong
ProblemSignWhat to do
Blown sproutsLoose, leafy, openFirm soil, stake, less nitrogen, steady water
Cabbage whiteShredded leaves, green caterpillarsInsect mesh from day one; pick off
AphidsGrey colonies inside the sproutsMesh; squash early. Hard to wash out later
PigeonsSeedlings and leaves strippedNetting
ClubrootStunted, wilting, swollen rootsLime to pH 7, rotate. No cure
Cabbage root flyYoung plants wilt and collapseCollars at the stem base, or mesh
WhiteflyClouds of tiny white fliesMostly cosmetic on a big plant

Fine insect mesh handles most of it at once

One barrier — fine mesh or insect netting over hoops, sealed at the edges, from planting day — excludes cabbage whites, pigeons, cabbage root fly and most aphids simultaneously.

It is far more effective than anything you can spray onto a plant whose sprouts are packed tight enough to hide an entire aphid colony.

Harvesting

  • Start once the lowest sprouts are firm and about an inch across
  • Work up the stem, bottom first. The upper ones keep sizing for weeks
  • Snap or cut each sprout off, and remove the leaf below it
  • Wait for a frost or two if you can. Cold converts starch to sugar, and the difference in taste is not subtle
  • Leave the plant standing through winter in most climates and pick as needed — it stores better on the stem than in a fridge
  • The top rosette is edible too, cooked like cabbage, once you are done picking

A single good plant carries 50 to 100 sprouts over a season stretching from autumn into midwinter. That long picking window is the real reason to grow them, given the space they take.

Common questions

When should I plant brussels sprouts?

Count backwards from your first autumn frost. The crop needs 80 to 130 days from transplanting depending on variety, and the sprouts want to mature in cool weather, so most gardeners sow indoors in mid to late spring — April or May in much of the northern United States and the UK — and transplant out in early summer. In mild-winter regions of zones 8 to 10 the better timing is a late-summer sowing for a winter harvest, because sprouts maturing in summer heat are bitter and loose.

Why are my brussels sprouts loose and leafy instead of tight?

Blown sprouts come from loose soil, too much nitrogen, or heat. Brussels sprouts need firm ground — this is the one vegetable that genuinely wants the soil trodden down before planting — because a plant rocking in soft earth or wind produces open rosettes instead of tight buttons. Heavy nitrogen feeding late in the season does the same thing, as does a hot spell while the sprouts are forming. Stake tall plants, firm them in, and stop feeding nitrogen by late summer.

When do you harvest brussels sprouts?

Once the lower sprouts are firm and about an inch across, which is typically after the first frost or two. Pick from the bottom of the stem upward, snapping or cutting each sprout off and removing the yellowing leaf below it, and leave the rest to keep sizing up over several weeks. Frost genuinely improves the flavour: cold converts stored starch to sugar, which is why sprouts picked in November taste sweet and the same plant picked in September tastes harsh.

How tall do brussels sprouts grow and do they need staking?

Two to three feet for most varieties, and taller in a good season, on a single heavy stem carrying up to a hundred sprouts. That top weight plus autumn wind topples plants regularly, and a rocked plant makes loose sprouts, so staking with a cane is worth doing on any exposed site. Earthing up soil around the base helps as well, and both are easier done at planting than after the plant has grown.

What are the main problems with growing brussels sprouts?

Cabbage white caterpillars stripping the leaves, aphids packing into the sprouts themselves where they are almost impossible to wash out, pigeons taking seedlings and mature plants alike, clubroot in acid soil, and cabbage root fly in the roots of young transplants. Fine insect mesh over the bed from planting day handles the first three at once, which is why it is the single most useful thing to do. Clubroot is prevented by liming to pH 6.5 to 7.0 and by rotation, never cured.

Should I cut the top off brussels sprout plants?

Topping — removing the growing tip in early autumn — pushes the plant to finish the sprouts it has rather than keep growing, and it makes the crop mature more evenly and sooner. That is useful in a short season or if frost is coming before the sprouts have sized up. It is a trade-off, though: topping stops further growth, so a plant topped too early yields less overall. In a long mild autumn, leave the tops on and pick over several weeks instead.

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