How to Grow Ashwagandha in Australia

Ashwagandha (Withania somnifera), a grey-leaved shrub of the nightshade family (Solanaceae), is grown for its fleshy root and its orange-red berries in papery husks. It is frost-tender and short lived, so outside the tropics it is grown from Ashwagandha Vedic seed as a summer annual. The seed needs warmth rather than any treatment, and it often fails in cold or soggy mix.

Three mistakes that matter

1. Sowing into cold mix. Cool mix slows and thins germination, and seed sown in open ground often fails, with heavy seedling losses. Raise seed warm under cover, as Germinating the seed describes.
2. Keeping the soil wet. Ashwagandha comes from dry country, and too much water harms it, rotting stems and roots. Plant it in free-draining ground or a raised bed, and water only once the top few centimetres have dried.
3. Lifting the root too early. A root dug before the plant matures is thin and small. Leave the plant in the ground until it shows the signs of maturity that Harvesting Roots describes.

When to plant

Warmth governs sowing: the seed wants 20 to 30°C, with about 25°C best. Start seed under cover about five weeks before planting out, and plant out after the last frost. In frost-free districts, sow direct or plant out once nights stay above 15°C. One sowing a year is enough, because a plant needs five to six months to make a root worth lifting.

In the cool south, Melbourne Cup weekend in early November is the usual marker for planting out frost-tender crops. Sow early in the window wherever autumn frost comes early, so the root has its full season before the first cold night.

Site, soil and setup

Dig a 5 cm layer of compost into the bed before planting. Where a pH test reads below 6.5, dig in garden lime at 100 to 200 g per square metre 4 weeks before planting. Do not plant where tomatoes, eggplant, capsicum or potatoes grew last season, because root-knot nematodes build up when susceptible crops follow one another.

Container growing

A pot suits cool districts, where the plant can go under cover before frost. It also suits wet ones, keeping the root out of soggy ground. Use a pot at least 30 cm wide, which holds about 13.5 L; a 40 cm pot, about 28 L, gives the root more room. Fill it with free-draining potting mix, with a few handfuls of coarse sand mixed through.

• Water: only once the top few centimetres of mix are dry, then water until it drains from the base.
• Feed: worm casting liquid diluted to weak tea colour, fortnightly from potting up until the first flowers.
• Position: full sun, sheltered from strong wind; move the pot under cover before the first frost.
• Saucers: empty them after rain, so the mix never sits in water.

Germinating the seed

Ashwagandha seed has no dormancy that a chill or a nick must break: it needs warmth. In a trial of two Indian seed lots, seed germinated best at 25°C and poorly at 20°C. Light helped a little, so cover the seed thinly. In that trial a three-hour rinse or a light scuffing lifted germination a little at 25°C, but no treatment helped much at 20°C. Ordinary stored seed stays viable for about a year, and then germination falls away; seed banks keep it far longer dried and frozen.

Rates vary between seed lots. Untreated seed in the Kew seed bank's tests gave 58 to 100 per cent, including lots tested at 20°C. The Indian seed lots gave 40 to 55 per cent at 25°C, with the first seedlings after about eight days and most within two weeks. Sow two or three seeds for each plant wanted.

In the same trial, gibberellic acid lifted germination further, but it is a laboratory treatment that home seed does not need. More on these methods is in Soaking, Scarification and Cold Stratification.

When nothing comes up

• Too cold. In one trial, seed at 20°C came up later and far less well than at 25°C, though some seed bank lots did well at 20°C. Move the tray onto a seedling heat mat and hold it near 25°C.
• Mix kept too wet. Soggy mix rots seed and invites damping off (seedlings rotting before or just after they emerge); let the surface dry slightly between waterings.
• Old or warm-stored seed. Germination drops after about a year; store packets sealed, cool and dry, and sow fresh seed first.
• Home-saved seed still damp. Seed that stays moist after harvest can be slow to germinate for months, so dry the berries fully before taking the seed out.
• Given up too soon. Seed bank tests run for four to six weeks or more; wait four weeks in warm mix before sowing again.

Sowing Seeds

Start ashwagandha in trays or cells as Germinating the seed sets out; sowing direct suits only warm, frost-free districts.

Starting under cover

• Fill cells or a tray with seed raising mix and water it before sowing.
• Sow two or three seeds per cell, 5 mm deep, and firm the mix gently. A 15-seed packet sown this way fills five to seven cells.
• Keep the mix at the warmth When to plant gives, moist but not wet, under a clear cover.
• Lift the cover once seedlings show and give them full light, so they do not stretch.
• Thin to the strongest seedling in each cell once the first true leaves open.

Sowing direct

In the tropics and the warm subtropics, sow direct once the soil holds the warmth When to plant gives. Cover the seed thinly and mark the row. Thin the seedlings to 45 to 60 cm apart about four weeks after sowing.

Transplanting

Seedlings reach planting size at about five weeks old. Harden them off first (get them used to outdoor sun and wind over about a week), as hardening off seedlings describes. Plant them 45 to 60 cm apart at the depth they grew in the pot, and water them in with seaweed solution at half strength.

Care by growth stage

Water decides this crop more than feeding: steady moisture while young, then restraint once plants are established.

If growth stalls in poor soil, a light application of all-purpose controlled release granular (NPK around 14-5-10) scratched into the soil can help.

Companion planting

Grow it among plants that like the same hot, lean, dry conditions, and away from its nightshade relatives.

Grows well with

• Thyme, which wants the same full sun, free-draining soil and little water.
• Lavender, which suits the same dry, sunny bed and lean soil.
• Oregano, a low spreader that shares the dry end of the garden.

Keep apart

• Tomato, eggplant and capsicum, which share the 28-spotted ladybird and two-spotted mite.
• Mint, which wants moist soil and runs through the bed.

Harvesting Roots

Lift the roots 150 to 180 days after sowing, once the lower leaves dry and the berries turn from green to orange-red.

• Water the bed the day before if it is dry, so the soil is moist for digging.
• Cut the stems off 1 to 2 cm above the ground.
• Loosen the soil wide of the plant with a garden fork and ease the taproot out whole, side roots included.
• Wash the soil off and cut the roots into pieces 7 to 10 cm long.
• Spread the pieces in one layer in an airy, shaded spot until they are hard and dry right through.
• Pick ripe berries separately if you want seed.

Store the dried root pieces in airtight tins or jars, labelled, in a cool, dark cupboard, to keep out damp and mould. For seed, dry the picked berries completely, then crush them and sift out the pale, flat seed.

Traditional use and history

The Sanskrit name ashwagandha means horse smell, after the strong smell of the root. The Ayurvedic Pharmacopoeia of India records two other Sanskrit names, Hayagandha and Vajigandha. In English the plant has been called winter cherry, Indian winter cherry and poison gooseberry.

In Ayurveda, the traditional medicine of India, the root holds a prominent place among the rasayana herbs. The Unani tradition also used the root, the seeds and the leaves. The English name Indian ginseng came from comparing it with the ginseng of Chinese tradition.

Linnaeus first described the plant in the eighteenth century as Physalis somnifera, placing it with the cape gooseberries, and the Latin somnifera means sleep-bearing. The genus name Withania honours Henry Witham, an English palaeobotanist of the early nineteenth century.

In India the roots were traditionally collected in winter, washed and cut into short pieces, much as Harvesting Roots describes for the garden.

Safety

Ashwagandha is sold as seed for growing, and nothing here is advice to eat or take any part of the plant. Anyone thinking of using a plant should first seek advice from a qualified health practitioner.

The name winter cherry also belongs to Jerusalem cherry (Solanum pseudocapsicum), a naturalised garden escape in every mainland state. All its parts are poisonous to people, especially the unripe fruit. Its bright orange-red berries, 10 to 15 mm across, hang bare below white, star-shaped flowers. Ashwagandha's smaller berries sit inside a papery husk, as on a cape gooseberry, and its flowers are small and yellow-green. A related species, Withania coagulans, is a different plant from the one in the packet.

Common problems

Plants blacken after a cold night. Ashwagandha is frost-tender, so lift the roots before the first frost, or move potted plants under cover. Read more

Tall, sparse plants with few berries. The plant cannot grow well in shade, so move it to the sunniest bed next season.

Pale, stretched seedlings. Too little light after germination stretches seedlings, so move the tray into bright light at once. Read more

Pests and diseases

No serious pest is recorded on the field crop; those below attack it overseas, or its nightshade relatives in Australia.

Two-spotted mite (Tetranychus urticae). Tiny mites feed under the leaves, leaving pale stippling and fine webbing, and are worst in hot, dry weather. Hose the undersides of the leaves, and avoid broad-spectrum sprays, which kill the tiny black ladybirds that eat mites. Read more

Aphids (Aphididae). Small green or yellow sap-suckers cluster on soft tips, leaving distorted growth and sticky honeydew. Knock them off with a strong jet of water, or spray insecticidal soap on the undersides of the leaves. Read more

28-spotted ladybird (Epilachna vigintioctopunctata). Downy, dull orange beetles and spiny, pale yellow larvae graze the leaf surface, leaving lacy patches. Hand-pick both, checking for the downy hairs that set them apart from aphid-eating ladybirds. Read more

Root-knot nematode (Meloidogyne species). Microscopic worms form galls 1 to 10 mm across on the roots, so plants look stunted and wilt. Bin galled roots, and rotate beds as Site, soil and setup describes. Read more

Damping off (Pythium species and Rhizoctonia solani). Seedlings rot before they emerge or collapse at soil level soon after, worst in hot, humid weather. Use fresh mix and clean trays, avoid overwatering and thin crowded seedlings. Read more

Prevention first

• Plant in full sun and free-draining soil, so plants are not stressed.
• Check the undersides of leaves weekly in hot, dry weather for mites and ladybird larvae.
• Water at the base in the morning, so leaves dry before night.
• Clear nightshade weeds near the bed, which carry pests and nematodes between crops.

Tips

1. Write the sowing date on each tray label, so the days to harvest in Harvesting Roots are easy to count.
2. Pick ripe berries before birds do, to keep self-sown seedlings out of nearby bushland.
3. In frost-free gardens, leave one plant in the ground for a second year, since it grows there as a short-lived perennial.