Swede- American Purple Top

How to Grow Swede from Seed

Family: Brassicaceae
Binomial name: Brassica napus var. napobrassica
Life Cycle: Biennial (usually grown as an annual)

When to Sow Swede Seeds

Swede is a cool season crop. Use the table below to identify the best time of year to sow swede in your climate.

Preparation

Swede plants are best grown in full sun or part shade. Choose a location that will receive at least 3 hours of full sun each day.

Swede plants need a loose, well drained soil enriched with organic matter. Prepare soil by weeding it thoroughly, digging it over to at least a spade’s depth to loosen the soil, and adding aged animal manure or compost. Organic matter can be dug into heavy soil to lighten it so roots can grow freely. Keep the area free of weeds until planting.

How to Sow Swede Seeds

Swede seeds do not require any treatment (eg soaking, stratification) before sowing.

Swede 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

1. Sow seeds directly in the garden 10mm deep and 20cm apart, with rows 50cm apart.
2. Keep soil moist but never wet or dry.
3. Seeds should germinate in around 4-10 days at a soil temperature of 16-30°C.
4. Young seedlings will need protection from pests, pets and weather until they are established.

Raise Seedlings

1. Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
2. Sow seeds 10mm deep.
3. Keep soil moist but never wet or dry.
4. Seeds should germinate in around 4-10 days at a soil temperature of 16-30°C.
5. Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
6. Plant out, spacing plants 20cm apart, with rows 50cm apart.

How to Grow Swede

Swede plants need regular 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. Fertilising can result in excessive leaf growth at the expense of roots forming. In poor soil use a fertiliser low in nitrogen and high in phosphorus, such as blood and bone, applied at the recommended rate.

How to Harvest Swedes

Swedes should be ready to harvest in approximately 100 days.

Roots are ready to harvest when they are large enough to eat, and can be harvested as needed. Harvest individual roots by gently pulling at the base of the leaves, or use a garden fork to lift multiple roots from the soil. Shake off any excess soil and cut the foliage 1-2cm above the top of the root. Store swedes in a perforated plastic bag in the fridge. For longer term storage, swedes can be canned or fermented.

Common Problems when Growing Swedes

Like all plants, swede is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing swede plants:

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  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.
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  Boron deficiency causes yellow leaf tips, hollow discoloured stems or soft brown centres in the roots. Dissolve 1 tablespoon of household boron in 5 litres of water in a watering can and apply when seedlings are 5-10cm tall. Do not use as a general fertiliser as boron is toxic to some plants.
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  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.
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  Split roots are usually caused by inconsistent watering when roots are mature. Water deeply and evenly to keep soil moisture consistent and always take recent or expected rainfall into consideration before watering.
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  Tough roots usually indicate that the roots were harvested too late. Harvest roots when they are young and tender.
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  Small roots can be the result of sowing too thickly or over fertilising. Thin seedlings to give roots adequate space to grow. Do not fertilise plants as this may encourage the growth of foliage at the expense of roots.