Japanese Turnips

Start from seed: February-March and August-October

Optimum soil temperature for germination: 15-21°C

Plant spacing: 10-15 cm

Days to maturity: 35-50 days

Introduction

Japanese turnips (Brassica rapa var. rapa), also known as Tokyo or Hakurei turnips, are a specialty vegetable in the Brassicaceae family, which includes broccoli, cauliflower, kale, kohl rabi, Brussels sprouts, turnips, radish, rocket, collards and mustard greens. If you are thinking turnips, think again, Japanese turnips are crisp and almost juicy – prized for their delicate flavour, tender texture, and quick maturity.

Developed in Japan during the 1950s as a response to food shortages following World War II, Japanese turnips were bred specifically for their fast growth, mild flavour, and versatility. The Hakurei variety, often called a “salad turnip,” has become particularly popular among chefs and home gardeners alike for its sweet, fruity taste and crisp texture when eaten raw.

Japanese turnips are characterized by their smooth, globe-shaped roots with pure white skin and flesh. They generally grow to about 5-8 cm in diameter, though they can be harvested when smaller for the most tender texture. The roots grow just below the soil surface, with attractive dark green leaves that are also edible and nutritious. Unlike some traditional turnip varieties, Japanese turnips are mild enough to eat raw in salads, as well as cooked in various ways, including steaming, roasting, or stir-frying.

Site and soil

Japanese turnips thrive in Canberra’s climate, particularly during the cooler seasons of spring and autumn. The best time to grow them is in early Spring. Since the tops and roots are eaten, they help fill “the hungry gap”.

They prefer full sun but will tolerate partial shade, especially during the warmer months when too much heat can cause bolting or lead to the roots becoming woody.

Prepare the soil well before planting by incorporating compost or well-rotted manure to improve fertility and drainage. Japanese turnips prefer a loose, well-draining soil with a pH between 6.0 and 7.0. Sandy loam is ideal, but they will grow in most soil types as long as the ground isn’t waterlogged. The soil should be worked to a fine tilth before sowing, as lumpy soil can cause misshapen roots.

For container growing, choose pots at least 20 cm deep with good drainage holes. Use a premium potting mix and consider adding extra compost for better nutrition. Containers work well for Japanese turnips due to their compact size and quick growth, making them suitable for small gardens or balconies. One advantage of container growing is the ability to move plants to more favourable conditions as the season progresses.

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

In Canberra, Japanese turnips can be sown during two main periods: February-March for autumn/early winter harvest, and August to October for spring/early summer harvest. Direct sowing is preferred over transplanting, as root vegetables generally don’t transplant well.

Sow seeds directly into prepared soil to a depth twice the size of the seed or sprinkle them in a shallow drill and lightly cover with soil. Rows can be 25-30cm apart, with seeds spaced about 2-3 cm apart within the row. After germination, thin seedlings to 10-15 cm apart to allow proper root development. You can use the thinnings in salads or stir-fries.

For a continuous harvest, consider succession planting every 2-3 weeks within the optimal sowing windows. This ensures a steady supply of fresh turnips rather than having them all mature at once.

After sowing, water the area gently but thoroughly and apply a light organic mulch to retain soil moisture and suppress weeds. Keep the soil consistently moist until germination, which typically occurs within 5-10 days depending on soil temperature.

Cultivation

Japanese turnips grow quickly and require little maintenance, making them ideal for beginner gardeners or those looking for a fast crop. However, paying attention to a few key aspects will ensure the best quality harvest.

Consistent moisture is essential for developing sweet, tender roots. Water regularly to maintain even soil moisture, especially during dry periods. Irregular watering can lead to splitting roots or woody texture. Avoid overwatering, as this can lead to disease problems.

If your soil was properly prepared before planting, additional fertilizer is unnecessary. A foliar spray early on 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. Avoid soluble nitrogen fertilizers, which can promote excessive leaf growth at the expense of root development.

Weed control is important, especially during the early growth stages when turnips can be overwhelmed by more aggressive plants. Hand weed carefully to avoid disturbing the developing roots, and maintain mulch to suppress weed growth.

Japanese turnips are cool-season crops that perform best when temperatures are between 15-20°C. In Canberra, they can withstand light frosts once established, which can actually improve their flavour by converting starches to sugars. During warmer weather, providing afternoon shade can help prevent bolting.

Harvesting

One of the advantages of Japanese turnips is their quick maturity. They can be harvested as early as 35 days after sowing, with most varieties ready to harvest within 40-50 days.

Harvest when the roots are about 5-8 cm in diameter, though they can be harvested smaller for a more delicate texture and flavour. Avoid leaving them in the ground too long, especially in warm weather, as they can become woody or develop a stronger flavour.

To harvest, gently loosen the soil around the root with a garden fork and pull the plant by grasping the base of the leaves. For a cleaner harvest, you can brush away the soil at the top of the root to assess its size before deciding to pull it.

Both the roots and the greens are edible. The tender greens can be harvested even before the roots are mature and used like spinach or other cooking greens. For the best flavour and texture, use freshly harvested turnips immediately, though they can be stored in the refrigerator for up to two weeks. Remove the leaves if storing for more than a few days, as they will draw moisture from the root.

Problems

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.

While Japanese turnips are generally trouble-free, they can face several challenges in Canberra gardens:

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.

Flea Beetles: These tiny black insects jump when disturbed and create small holes in the leaves, giving them a shot-hole appearance. They are particularly problematic during warm, dry weather. Control methods include floating row covers placed immediately after sowing, regular watering to discourage beetles, and organic insecticidal soaps for severe infestations.

Root Maggots: The larvae of the cabbage root fly can tunnel into the developing roots, causing damage and opening pathways for disease. Prevent infestations by using floating row covers secured at the edges to prevent the flies from laying eggs near the plants.

Slugs and Snails: These pests can damage young seedlings and create holes in leaves and roots. Control using beer traps, copper tape barriers, or organic (Iron EDTA) snail baits.

Bolting: Heat or water stress can trigger premature flowering. Plant during cooler seasons and ensure consistent watering during warm weather to reduce this risk.

Recommended Varieties

Several Japanese turnip varieties perform well in Canberra’s climate:

Hakurei: The most popular Japanese turnip variety, prized for its sweet flavour and crisp texture. Dark green, hairless tops. It matures quickly (35-40 days) and produces smooth, white roots that are excellent raw or cooked. This F1 hybrid sets the standard for salad turnips.

Tokyo Market (Tokyo Cross): An open-pollinated variety with a slightly flattened root shape. It has a mild flavour and matures in about 35-45 days. Good resistance to bolting makes it suitable for Canberra’s variable climate.

Hirosaki Red: Adds colour to the garden with its bright red skin and white flesh. It has a slightly spicier flavour than white varieties but is still milder than Western turnips. Matures in 40-45 days.

Shogoin: A larger Japanese turnip that grows up to 10 cm in diameter while maintaining tenderness. The roots are slightly flattened with a good storage life. Matures in 50-60 days.

For Canberra gardens, Hakurei or Tokyo Cross are recommended as the most reliable variety with the best flavour profile, especially for those new to growing Japanese turnips. For a continuous harvest, consider planting both early-maturing varieties like Hakurei and slightly later ones like Shogoin.

References

Johnny’s Selected Seeds. (2024). Hakurei – Salad Turnip Seed. https://www.johnnyseeds.com/vegetables/turnips/hakurei-f1-turnip-seed-706.html
West Coast Seeds. (2024). Hakurei Turnip Seeds. https://www.westcoastseeds.com/products/hakurei
Yates Australia. (2024). Japanese Turnip Hakurei. https://www.yates.com.au/seeds/vegetables/japanese-turnip-hakurei/