How to Grow Moldavian Dragonhead in Australia

Moldavian dragonhead (Dracocephalum moldavica) is grown for its lemon-scented leaves and whorls of violet-blue flowers, an annual herb of the mint family, Lamiaceae. Unlike most traditional herbs it is an easy seed. The one step to get right comes first: the seed needs light, so seed buried like a bean often fails.

Three mistakes that matter

1. Burying the seed. Dragonhead seed needs light to germinate, so seed raked in or covered with mix can sit in the dark and fail. Press it onto moist soil and leave it uncovered, as Germinating the seed explains.
2. Sowing late into the heat. Plants sown early reach flowering before hot weather, while late sowings run up and finish early once the heat arrives. Sow at the cooler end of your zone's window, as When to plant sets out.
3. Cutting too late. Stems left long after the first flowers open turn coarse, with fewer good leaves. Cut the tops in early flower and again as new spikes form, as Harvesting Sprigs describes.

When to plant

Mild weather suits this seed: in the Kew seed bank's test it germinated well with 12-hour days at 21°C and nights at 11°C. Sow direct from about two weeks before the last frost, or start seed under cover and plant out once frosts are over. One sowing can give two or three cuts over the season, because cutting brings on fresh flowering stems.

Site, soil and setup

Dragonhead grows best in full sun and takes part shade. It has a mild appetite for compost and water, so a moderately fertile bed that drains freely suits it better than a heavily manured one. Plants usually reach 20 to 60 cm tall, so they suit the front of a bed or a pot.

Container growing

Choose a pot about 30 cm across, which holds 10 to 15 L of mix, with good drainage holes. Fill it with quality potting mix and sow three or four seeds on the surface, then thin to the strongest one or two plants. The store sells a single, unnamed seed line, and its plants stay small enough for a pot on a sunny balcony.

• Water: check the mix daily in warm weather and keep it evenly moist, never soggy.
• Feed: seaweed solution at half strength, 15 mL per 9 L, once a fortnight while you are cutting.
• Position: full sun, or morning sun and afternoon shade where summers are hot.

Germinating the seed

Moldavian dragonhead seed has no dormancy to break. It needs only moisture, mild temperatures and light. Seed farms in North America advise surface sowing, and the Kew seed bank tested it under 12 hours of light a day. The seed is small, around 450 to 650 to the gram, so a pinch sows a row.

Kew recorded 90 per cent germination with no treatment, and a seed farm that grows it describes germination as easy. In a warm, bright room, seed can sprout within three days. Sow two or three seeds for each plant you want, then thin to the strongest.

No soaking, chilling or scarifying is needed; the guide to seed treatments explains which seeds do need them. Stored seed keeps well: one storage trial recorded better than 98 per cent germination after three years at 5°C to 10°C. A collection in the Kew seed bank still gave 83 per cent after 15 years.

When nothing comes up

• Covered too deep: seed buried in the dark often fails, so resow on the surface and press it in.
• Surface dried out: uncovered seed dries fast, so mist it daily or cover the tray until seedlings show.
• Washed away: a hard jet scatters fine seed, so water with a fine rose, as watering seeds and seedlings shows.
• Too cold: seed sown into cold, wet soil sits still, so wait for milder days or start it indoors.
• Old or warm-stored seed: seed keeps for years cool and dry, but loses life stored warm or damp.
• Given up too soon: allow three weeks before resowing, then check the causes in why seeds fail to germinate.

Sowing Seeds

Sow Moldavian Dragonhead seeds untreated, direct where they will flower, or in trays for an earlier start where frost lingers.

Sowing direct

• Rake the bed to a fine, level surface and water it the day before sowing.
• Scatter seed thinly and press it onto the moist soil without covering it, as sowing tiny seeds shows.
• Keep the surface damp with a fine spray until seedlings appear, usually in 10 to 15 days.
• Thin to 15 to 30 cm apart once seedlings carry their first true leaves.

Starting under cover

• Sow two or three seeds onto each cell of moist seed raising mix, pressed in and uncovered.
• Keep the tray bright and damp; seedlings that stretch are short of light, as leggy seedlings explains.
• Thin to one seedling per cell, snipping the extras at soil level.
• Harden off (gradually accustom seedlings to sun and wind over a week), as hardening off seedlings describes.
• Plant out 15 to 30 cm apart once frosts are over.

Care by growth stage

Steady moisture in free-draining soil, and cutting on time, decide this crop.

If growth stalls in poor soil, a light application of all-purpose controlled release granular (NPK around 14-5-10) scratched in around the plants can help. Mulch lightly once seedlings are established, to hold moisture and keep weeds down.

Pinching and Harvesting

Pinch young plants early so they branch, and keep cutting through the season.

• Growing tips: pinch them out on young plants once they carry several pairs of leaves, so each stem branches.
• Flowering tops: cut them in early flower, just above a pair of leaves, leaving leafy stems below to regrow.
• Spent spikes: cut them off as the flowers fade, which encourages more blooms.
• Single leaves: pick a few at any time once plants are bushy, spreading the picking across the plant.
• Seed plants: leave a few plants uncut late in the season to ripen seed for next year.

Companion planting

Dragonhead earns a place near crops that need bees, and it suits a sunny spot with other herbs of the same size.

Grows well with

• Pumpkins and zucchini, whose flowers need bees to set fruit, and dragonhead flowers draw bees in numbers.
• Basil, which is of similar size and wants the same sun, soil and water.

Keep apart

• Mint, whose vigorous runners spread through a bed and crowd out a small annual.
• Tall corn and sunflowers, which shade a sun-loving herb planted to their south; grow dragonhead on their northern side.

Harvesting Sprigs

Cut sprigs when the first flowers open on the spikes, usually 11 to 13 weeks after sowing.

• Cut the leafy flowering tops with secateurs, as Pinching and Harvesting describes.
• Tie the stems in small, loose bunches for drying.
• Strip the leaves and flowers from the stalks once they are dry and crisp.

Hang the bunches in shade at room temperature, where they dry in about a week. Heat changes the scented oils, and one drying trial rated leaves dried at 20°C the best, so avoid an oven or hot shed. Store the dried leaves and flowers in a sealed jar out of the light, where they keep their aroma well.

Use fresh leaves and flowers as a lemon-scented flavouring in cold drinks, fruit desserts and syrups.

Traditional use and history

The genus name joins the Greek words for dragon and head, after the shape of the flower. Linnaeus named the species in the mid eighteenth century and recorded its home as Moldavia, the region behind the common name. It is native to temperate Asia, from Siberia and Central Asia to northern China, and has become naturalised across much of Eurasia.

Beekeepers value it as a honey plant, because its flowers make large amounts of sugary nectar, and Swedish gardeners know it as Turkish dragon flower.

It is also grown as an ornamental and for its scented oil. The national plant census lists it as doubtfully naturalised in New South Wales, from a record near Barraba on the North West Slopes.

Safety

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

Keep the name straight when buying seed. False dragonhead, or obedient plant (Physostegia virginiana), is a different plant of another genus that shares the common name. Moldavian dragonhead is also sold as Moldavian balm, so check the botanical name on the packet.

Common problems

Bare patches in the row. Seed covered too deeply or allowed to dry out on the surface are the usual causes; Germinating the seed sets out each fix.

Plants yellow and collapse. Waterlogged soil rots the roots, so plants on heavy, wet ground fail first; follow the advice on waterlogged soil.

Plants finish early in summer. Heat after a late sowing is the likely cause, as Three mistakes that matter explains.

Pests and diseases

No pest or disease specific to dragonhead is recorded in Australia, so the risks below are general garden ones.

Two-spotted mite (Tetranychus urticae). Found throughout Australia on a very wide range of plants, it feeds under the leaves and leaves pale stippling and fine webbing. It is worst in hot, dry weather. Hose the undersides of the leaves, and avoid broad-spectrum sprays, which kill the predators that eat mites. Read more

Common garden snail (Cornu aspersum). Snails feed at night, early in the morning and in rainy, overcast weather, and they can damage seedlings. Hand-pick them after dark in cool, wet spells. Read more

Damping off (Pythium species and Rhizoctonia solani). These soil fungi and water moulds rot seedlings of almost every crop, which collapse at soil level. Use fresh seed raising mix and clean trays, and keep the mix moist rather than wet. Read more

Prevention first

• Sow thinly and thin on time, so air moves between seedlings.
• Water at the base in the morning so leaves and soil surface dry by night.
• Check the undersides of leaves weekly in hot, dry spells.
• Clear boards, pots and weeds where snails shelter near seedlings.

Tips

1. Save seed from the few plants left uncut. Once their spikes turn brown and dry, cut them, rub the seed out and shake it over a sieve, which holds back the chaff.
2. Store the clean seed in a paper bag labelled with its name and date, somewhere cool and dry, ready for the next spring sowing.
3. Use spare seedlings to fill gaps in a summer flower border, where the violet-blue spikes last for weeks.