Cabbage

Start from seed: November-February and September

Optimum soil temperature for germination: 7-35°C

Plant seedlings: November-February and September

Plant spacing: 30-40 cm

Days to maturity: 60-120 days

Introduction

Cabbage (Brassica oleracea) is a versatile vegetable that belongs to the Brassicaceae family, which also includes broccoli, cauliflower, kale, kohl rabi, Brussels sprouts, turnips, radish, rocket, collards and mustard greens.

Cabbage has been cultivated for more than 4,000 years and was likely domesticated in Europe before 1000 BCE. Ancient Romans and Greeks valued cabbage for both culinary and medicinal purposes. The vegetable spread throughout northern Europe, becoming a dietary staple, and was introduced to Australia with European settlement.

Cabbage plants have compact, round or conical heads formed by overlapping leaves around a short stem. Varieties include green, red, savoy (with crinkled leaves), and cone-shaped. The compact heads are packed with nutrients and can be eaten raw in coleslaws and salads, fermented into sauerkraut, or cooked in various dishes.

Site and soil

Cabbage can be successfully grown in Canberra, particularly with careful variety selection and timing. Being generally a cool-season crop, cabbage performs best with full sun in spring and autumn but can benefit from afternoon shade during summer.

Prior to planting, prepare the soil by incorporating compost and a balanced organic fertilizer. Cabbage prefers a fertile, well-drained soil with a pH between 6.0-6.5. It is commonly thought that they prefer alkaline soil. This is because clubroot disease can be problematic in acidic soils. If this is the case liming to raise the pH above 7.0, ideally to 7.8, is beneficial.

If growing in pots, use a premium potting mix boosted with compost and complete organic fertiliser. Containers should be at least 30 cm deep and wide.

For details on preparing soil and pots, including the use of lime, dolomite, gypsum and fertilizers, please refer to the COGS guide to garden bed preparation.

Planting Seeds and Seedlings

Cabbage can be grown easily from seeds or seedlings. For autumn/winter cabbage, start seeds in November-February and for late spring cabbage, start seeds in September. Consider staggering plantings and growing different varieties to extend your harvest period.

Sow seeds in trays or pots filled with seed-raising mix, planting at a depth of approximately twice the diameter of the seed. Germination rates for brassica seed are usually 100% so be prudent when sowing seed. Keep the soil consistently moist but not waterlogged. Germination typically occurs within 4-10 days at optimum soil temperatures of 7-35°C.

Once seedlings develop 4-5 true leaves, they can be transplanted into individual pots to grow on before planting outdoors. This usually takes about 4-6 weeks from sowing. To grow strong seedlings, it is best to hold your nerve and do not overwater or over feed. Ideally the roots should fill the cell trays or pots prior to planting out and seedlings should be a little hungry. Soft, sappy seedlings are prone to dying shortly after planting out.

Plant seedlings approximately 30-50 cm apart depending on the type of cabbage. Large savoy cabbages will need to be planted further apart than compact sugarloaf cabbages. After planting, water them in with a seaweed solution. Mulch the soil around plants with organic matter such as straw, sugar cane mulch or leaf mould to retain moisture and suppress weeds.

Cultivation

In Canberra, the ideal time to plant cabbage seedlings outdoors is in spring, summer and early autumn avoiding the coldest winter months and the heat of summer. Large heading cabbages, such as Savoys, need to be planted out in December to finish growing before the daylength falls below 10 hours in May.

Young cabbage plants benefit from regular, consistent watering. Water deeply once or twice a week, rather than frequent shallow waterings, to encourage deep root development. Aim to keep the soil moist but not waterlogged.

Cabbage is a heavy feeder and benefits from side dressing with a balanced organic fertilizer half way through the growing season. A monthly foliar spray with seaweed solution; a mix of worm juice, seaweed and compost tea; or trace elements will help boost growth and resilience to pests and diseases.

Weeds can compete with cabbage plants for nutrients and water, so keep the area around plants weed-free, especially when plants are young. Mulching will help suppress weeds and retain soil moisture.

In hot weather, cabbage heads may split if exposed to heavy rain or irrigation after a dry period. To prevent splitting, maintain consistent soil moisture and twist the plant slightly or cut a few roots by pushing a spade into the soil on one side of the plant when the head is firm but not fully mature. Some varieties seem more prone to splitting than others.

Harvesting

Cabbage is ready to harvest when the head is firm and has reached the expected size for the variety, usually 60-120 days after transplanting, depending on the variety and growing conditions.

To harvest, cut the head off at the base using a sharp knife, leaving the outer wrapper leaves on to protect the head. For spring-planted cabbage, harvest before hot summer weather causes the heads to split or bolt. For summer and autumn-planted cabbage, harvest before severe winter frosts. Savoy cabbages are the most frost hardy.

Some varieties, particularly green cabbage, store well for several weeks in a cool, humid place. Remove any damaged outer leaves before storage.

Problems

There are numerous pests and diseases that can affect cabbage. The best approach is to have a reliable Australian reference book to identify problems. Garden Pests, Disease and Good Bugs by Denis Crawford is recommended.

A general strategy to follow with any problem is to observe the plant carefully before taking action. Identify the problem then carefully consider the course of action. For example, with pest insects, you often can see a predator nearby. If you watch and wait the predator may deal with the problem for you. Beneficial predatory insects which feed on pest insects can be purchased from suppliers such as Bugs for Bugs. If the problem needs further action the above recommended book has suggestions.

Practicing good garden hygiene, crop rotation, and maintaining plant vigour by providing adequate nutrients are key strategies for prevention.

There are several pests and diseases that can affect cabbage in Canberra.

Cabbage White Butterfly (Pieris rapae): This common pest lays tiny white eggs on the undersides of leaves. The green caterpillars that hatch are perfectly camouflaged and feed on leaves, creating irregular holes and contaminating plants with their droppings. Exclusion netting is the most reliable method to prevent damage from cabbage white butterfly. Keep in mind that the netting also excludes beneficial insects and birds that glean plants cleaning up other pests. Thus, leaving the netting on for too long can result in populations of sap suckers such as aphids, thrips and white fly building up inside the netting.

Control methods include:

Covering plants with fine insect mesh or exclusion netting from the time of planting
Regularly inspecting and manually removing eggs and caterpillars
Using biological controls such as Bacillus thuringiensis (also known as Bt and sold as Dipel) for significant infestations
Creating butterfly decoys by placing white plastic pieces around plants
Avoiding brassica weeds that act as hosts

Clubroot (Plasmodiophora brassicae): This soil-borne disease causes swollen, deformed roots and stunted growth. Plants may wilt during warm weather and show yellowing leaves. The disease thrives in acidic soils (below pH 7.0) and can persist in soil for many years. Management includes:

Maintaining soil pH above 7.0, ideally 7.8, through liming
Practicing crop rotation (avoid planting brassicas in the same area for at least 4 years)
Improving drainage in wet areas
Removing and disposing of infected plants (do not compost)
Using disease-free transplants and clean tools

Aphids, thrips and white fly: These small sap-sucking insects can transmit celery mosaic virus. They often cluster on the undersides of leaves, causing distortion and stunting. Small populations can be controlled by washing them off with a strong stream of water or using insecticidal soap. Alternatively, neem oil or pyrethrin can be used. Beneficial predators like ladybugs and lacewings should be encouraged and can be purchased for release on the crop. Look for aphid mummies which are evidence that the aphid has been parasitised. Eggs can also be parasitised and will appear bronze in colour. Generally speaking, plants that are high in soluble nitrogen (nitrates and ammonia) are prone to attack by sap sucking insects. Ideally avoid using soluble nitrogen fertilisers and ensure plants have adequate trace elements. This can be achieved by using foliar sprays.

Recommended Varieties

For Canberra’s climate, select varieties that are suitable for cool temperate conditions. The following varieties have been grown successfully in Canberra.

Green Cabbage:

Teama or Jersey Wakefield– conical-shaped, early maturing and sweet
Golden Acre – compact heads, good for smaller spaces
Savoy King – crinkled leaves, frost tolerant

Red Cabbage:

Red Express – early maturing with compact heads
Kalibos – cone shaped, sweet heads, good flavour

References

Bubel, Nancy. The New Seed-Starters Handbook. Rodale Books, 2018.
Crawford D. Garden Pests, Disease and Good Bugs. Australia: ABC Books; 2015.
Department of Primary Industries and Regional Development. (n.d.). Managing clubroot in vegetable brassica crops. https://www.agric.wa.gov.au/broccoli/managing-clubroot-vegetable-brassica-crops
Dove, Helena. Botany of the Kitchen Garden, Kew Publishing, Royal Botanic Gardens Kew, UK, 2023.
Fanton, Michel and Jude. The Seed Savers Handbook. The Seed Savers Network, Australia, 1993.
Johnny’s Selected Seeds. (2022). Growing Cabbage From Seed. https://www.johnnyseeds.com/growers-library/vegetables/cabbage/cabbage-key-growing-information.html
Yates Australia. (2024). How to Grow Cabbage. https://www.yates.com.au/how-to-grow/cabbage/