How to Grow Brussels Sprouts from Seed
Family: Brassicaceae
Binomial name: Brassica oleracea gemmifera
Life Cycle: Biennial (usually grown as an annual)
When to Sow Brussels sprouts Seeds
Brussels sprouts is a cool season crop. Use the table below to identify the best time of year to sow Brussels sprouts in your climate.
| JAN | FEB | MAR | APR | MAY | JUN | JUL | AUG | SEP | OCT | NOV | DEC | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cool | ||||||||||||
| Temperate | ||||||||||||
| Sub-Tropical | ||||||||||||
| Tropical | ||||||||||||
| Arid |
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Preparation
Brussels sprouts plants are best grown in full sun. Choose a location that will receive at least 6 hours of full sun each day.
Brussels sprouts plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting.
How to Sow Brussels sprouts Seeds
Brussels sprouts seeds do not require any treatment (eg soaking, stratification) before sowing.
Brussels sprouts seeds can be sown directly into the garden OR seedlings can be raised in trays or other containers and transplanted to the garden once established.
Sow Direct
- Sow seeds directly in the garden 6mm deep and 50-75cm apart, with rows 90-100cm apart.
- Keep soil moist but never wet or dry.
- Seeds should germinate in around 7-14 days at a soil temperature of 7-25°C.
- Young seedlings will need protection from pests, pets and weather until they are established.
Raise Seedlings
- Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
- Sow seeds 6mm deep.
- Keep soil moist but never wet or dry.
- Seeds should germinate in around 7-14 days at a soil temperature of 7-25°C.
- Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
- Plant out, spacing plants 50-75cm apart, with rows 90-100cm apart.
Brussels sprouts is a cool season crop that will bolt in very hot weather. Do not transplant seedlings or sow seeds outside in very warm temperatures.
How to Grow Brussels sprouts
Brussels sprouts plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.
If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a balanced fertiliser or one formulated for fruit and vegetables can be beneficial:
- Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
- Apply liquid fertiliser at the recommended rate and frequency while plants are fruiting or flowering.
How to Harvest Brussels sprouts
Brussels sprouts should be ready to harvest in approximately 80-140 days.
Brussels sprouts is ready to harvest when the heads are firm, green and 4-5cm in diameter. Twist the heads until they separate from the plant, starting with the lower ones first. Harvest only what you need as new heads may form further up the stem after the initial harvest. Store Brussels sprouts in a perforated plastic bag in the fridge. For longer term storage Brussels sprouts can be blanched then frozen.
Common Problems when Growing Brussels sprouts
Like all plants, Brussels sprouts is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing Brussels sprouts plants:
Aphids are small (2-4mm long) sap-sucking insects that congregate on the new shoots or the undersides of leaves. They can cause leaves to wilt or become discoloured, and also excrete honeydew which can attract ants and other insect pests. To manage aphids, remove them by spraying with a garden hose, apply a soap or alcohol spray, or encourage predatory insects to your garden. Read more about aphids here.
Bitter taste can be caused by plants growing too slowly, suffering a setback in growth or being harvested too late. Enrich soil with aged manure before planting, ensure plants are watered deeply and regularly, and harvest when they are young and tender.
Bolting is when a plant prematurely flowers and goes to seed. Bolting can be caused by a period of extreme weather. Avoid sowing seed until after the danger of frosts has passed or in very hot weather. Water plants regularly and deeply in hot weather to prevent them suffering heat stress.
Cabbage moth and cabbage white butterfly have white or grey wings with distinctive markings. They lay their eggs on the underside of leaves. Their caterpillars feed on the leaves, creating large holes and sometimes skeletonising the leaves. Use netting to exclude butterflies and moths or decoys to deter them. Pick the caterpillars off the plants or use an appropriate spray in a selective and targeted way. Read more about cabbage moth and cabbage white butterfly here.
Cutworms are moth larvae that live in the soil, emerging at night to feed. The caterpillars are 3-4cm long and white, grey or brown in colour. They can chew through the stems of tender seedlings, felling them at ground level. Remove cutworms by hand at night or use cardboard collars to protect the stems of seedlings.-
Heads not forming is usually caused by warm weather or by growing plants too slowly, without adequate water or nutrients. In warm climates, grow Brussels sprouts in winter to avoid extreme temperatures. Water regularly and ensure adequate compost or fertiliser is applied. 
Possums, birds and other animals can ruin a large percentage of your harvest overnight. Physically exclude pests by using netting or cages, or try spraying plants with a pungent homemade spray made from garlic, fish oil or mustard..jpg)
Powdery mildew is caused by fungal spores reproducing on the leaves of plants. First showing as white spots on leaves, affected areas areas can spread quickly to cover the entire leaf surface. While rarely fatal, powdery mildew can reduce yields. Water plants at soil level (not on the leaves) to prevent spreading spores, allow good air flow between plants, remove affected leaves and if necessary spray with an appropriate fungicide or homemade spray. Read more here about powdery mildew here.
