How to Grow Echinacea in Australia

Echinacea, the coneflower, is a long-lived prairie daisy of the family Asteraceae, grown for pink to purple flowers that bees and butterflies work all summer. Two species grow from seed: purple coneflower (Echinacea purpurea), white 'White Swan' included, and narrow-leaved coneflower (Echinacea angustifolia). Both shrug off heat and dry spells once settled; most failures come at the seed, because narrow-leaved coneflower needs weeks of cold to germinate.

Three mistakes that matter

1. Sowing narrow-leaved seed straight from the packet. Untreated seed of this species often gives almost no seedlings, because the embryo waits for a spell of cold and damp. Poor, erratic germination is the main obstacle growers report, so chill the seed first, as Germinating the seed describes.
2. Rich, wet soil. Echinacea crowns rot in soggy ground, and generous feeding gives soft stems that flop. Plant in free-draining soil in full sun, water deeply but seldom once plants have settled, and feed sparingly.
3. Leaving seedlings too long in the tray. Narrow-leaved coneflower sends a taproot straight down, and seedlings held back in small cells sulk after transplanting. Sow into deep cells and plant out within about four weeks of sowing.

When to plant

Echinacea seed germinates best at about 18 to 25°C. Sow under cover as days warm in late winter, or outdoors once spring soil has warmed. Plant out after the last frost. One sowing gives clumps that flower for years, so there is no need to sow again each season.

In frosty districts, narrow-leaved seed can instead go into pots left outdoors over late autumn and winter. The weather chills it, and seedlings appear in spring.

Site, soil and setup

Narrow-leaved coneflower comes from dry, rocky Great Plains prairie and needs sharp drainage. Purple coneflower, from moister prairies and open woods, takes most soils that never stay waterlogged.

Container growing

A pot suits echinacea wherever the garden soil stays wet, because the gardener controls the drainage. Give one plant a pot at least 30 cm wide and about 27 cm deep, which holds about 13.5 L. Tall purple coneflower is happier in a 33 cm pot of about 18 L. The shorter types suit pots best: narrow-leaved coneflower at about 30 to 60 cm, and 'White Swan' at about 60 to 90 cm.

• Mix: a free-draining potting mix, with a few handfuls of coarse sand if it stays wet.
• Water: when the top few centimetres are dry, until water runs from the holes; never leave the pot in a full saucer.
• Feed: worm casting liquid diluted to weak tea colour, fortnightly in spring only.
• Position: full sun, out of strong wind; the plant dies back in winter, so keep the mix barely moist until shoots return.

Germinating the seed

Purple coneflower and 'White Swan' have little dormancy: fresh seed often germinates at 70 to 84 per cent with no treatment. A few weeks of cold speeds it up and evens it out. In one study, 1 to 4 weeks of chilling lifted a poor batch from under 40 per cent to over 90 per cent.

Narrow-leaved coneflower is the hard one: its embryo stays dormant until it has been through cold and damp. Fresh seed has given 0 to 6 per cent in trials. After cold moist stratification (weeks of damp storage in the cold), 60 to 80 per cent is realistic, with seedlings in 1 to 3 weeks.

Sow two seeds per cell of purple coneflower and two or three of narrow-leaved coneflower, then thin to the strongest. Leave the seed coat alone. Trimming it halved germination of chilled narrow-leaved seed in one trial, and the coat removal that helped in another was laboratory work.

The packet notes for narrow-leaved coneflower suggest a brief, dilute bleach soak before chilling. In germination trials, a similar soak serves only to sterilise the seed surface; the cold is what ends dormancy. Nurseries sometimes use plant growth regulators as well, but chilling alone does the job at home. For the principles, see Soaking, Scarification and Cold Stratification.

When nothing comes up

• Buried too deep: light helps narrow-leaved seed, so press it onto the surface and barely cover it.
• Bag dried out or went mouldy: check it weekly and add a few drops of water if it feels dry. Sow at once if roots or mould appear.
• Too cold or too hot: keep trays at the temperature When to plant gives, off cold windowsills and out of hot glasshouses.
• Not enough cold: narrow-leaved seed chilled for under 2 weeks often stays dormant; chill it again for 4 weeks.
• Old seed: seed kept cool, dry and dark stays viable for about three years; older or warm-stored seed fades.
• Given up too soon: wait 4 weeks in the warm before re-chilling and sowing again; seed sown outdoors in autumn may wait until spring.

Sowing Seeds

Start echinacea from seed treated as Germinating the seed describes, in deep cells under cover; purple coneflower can also be sown direct.

Starting under cover

• Fill cells or tubes at least 10 cm deep with seed-raising mix, so the taproot grows straight down.
• Cover purple coneflower with a light sifting of mix; press narrow-leaved seed onto the surface and barely cover it.
• Keep the mix at the temperature When to plant gives, and mist it so the surface never dries.
• Move trays into full light as soon as seedlings show, so they do not stretch.

Sowing direct

Purple coneflower can be sown into a prepared bed in spring once the soil has warmed. Trials report patchy stands from sowing in the open, though, so raising seedlings is more reliable. Scatter seed thinly, cover it lightly and keep the surface damp until seedlings appear.

Transplanting

• Plant out about 20 to 30 days after sowing, before narrow-leaved seedlings grow past their first true leaves.
• Harden off first (hardening off means giving seedlings a few hours outdoors each day, building up over about a week), as hardening off seedlings explains.
• Space narrow-leaved coneflower 30 cm apart, and purple coneflower and 'White Swan' 40 to 45 cm apart.
• Set each plant at the depth it grew, firm the soil gently and water in well.
• Weed by hand through the first year, because young plants cannot compete.

Care by growth stage

Drainage and sun decide the crop far more than feeding. Echinacea grows wild in lean prairie soil, and extra nitrogen weakens its roots and makes stems flop.

If growth stalls in very poor sand, a light application of all-purpose controlled release granular (NPK around 14-5-10) scratched in each spring can help. At Mingoola, in the Dumaresq River valley, one echinacea grower keeps nitrogen low because too much darkens the flowers when they are dried.

Cutting Back

Deadheading prolongs flowering, so snip spent flowers back to a leaf or side bud through summer. In autumn, leave the last heads standing for seed, self-sown seedlings and seed-eating birds.

• Cut dead stems and leaves to the ground in winter, before new shoots appear.
• Lift and divide crowded clumps every 3 to 4 years in autumn or early spring, as dividing perennials shows.
• Pull out and bin any plant with green, leafy flower heads or bunched shoots, rather than cutting it back.

Companion planting

Echinacea does best beside plants that want the same sun, lean soil and occasional water.

Grows well with

• Salvias, whose upright spikes contrast with the cones and share their dry conditions.
• Rudbeckia, a fellow prairie daisy for the same sunny border.
• Ornamental grasses, which fill gaps between clumps and let air move through.
• Lavender, which also wants full sun and free-draining soil.

Keep apart

• Mint, whose spreading runners invade the clump and want wetter soil.
• Leafy crops such as lettuce, whose frequent watering can rot echinacea crowns.

Harvesting Flowers and Roots

Cut flowers once the petals have opened, and gather seed heads when the cones are dark and dry in autumn. Lift roots only from plants three to four years old.

• Cut vase stems as the flowers open and stand them straight in water.
• For dried flowers, cut stems at or near full bloom and hang them in a dark, airy place.
• Gather ripe seed heads in autumn, before birds strip them, and dry them fully.
• Lift roots in late autumn or winter, once the leaves have turned brown.
• Wash the roots, then dry them on racks in an airy place for two to four days, kept below 43°C.
• Replant part of the crown with its fine roots spread out, so the clump carries on.

Store dried roots and flowers once fully dry, in bags kept dark, cool and dry, away from mice and insects, for a year at most.

Traditional use and history

The name comes from the Greek echinos, meaning hedgehog or sea urchin, for the spiny cone. In North America the plants also went by Kansas snakeroot, comb flower and black sampson. The ethnobotanist Melvin Gilmore wrote that the plant seems to have been used for more ailments than any other in the Missouri River region.

European settlers took up the root in the early nineteenth century. In the same years, at Fort Mandan, Meriwether Lewis sent root east with a letter for President Thomas Jefferson describing its uses. By the early twentieth century, echinacea preparations were among the best-selling medicines made from an American plant. Cultivation has since spread to nearly every continent, including farms in the Dumaresq River valley at Mingoola.

Wild stands have paid for that demand. Harvesters dug an estimated 700,000 narrow-leaved coneflower plants from northeastern Montana in a single year. The United States Department of Agriculture records wild populations dwindling from habitat loss and over-harvesting. A relative, smooth coneflower, is listed as threatened under United States federal law.

Safety

These seeds are sold for growing. 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.

Common problems

Stems flop or lean. Rich soil, heavy feeding or too much shade makes tall, soft growth, so move clumps into full sun and stop feeding.

No flowers in the first summer. Seed-grown plants often need a second year to size up, though purple coneflower sown early under cover often flowers in its first.

Seedlings keel over at the soil line. Damping off (a fungal rot of young stems) strikes in cold, wet, crowded trays, so sow thinly and water from below. Read more

Pale, stretched seedlings. Too little light makes seedlings stretch and topple, as Starting under cover warns. Read more

Scorched leaves near the sea. Salt spray burns echinacea, which tolerates it poorly, so plant it behind a windbreak or in a pot away from the spray.

Seedlings chewed or gone overnight. Snails and slugs graze young seedlings, so look for slime trails and check under leaves and nearby rocks, where they shelter by day. Read more

Pests and diseases

Echinacea is seldom badly troubled, and most trouble starts with crowding or wet soil.

Aphids (Aphididae). Colonies of small, soft-bodied bugs cluster on buds and soft stems in spring and distort new growth. Hose them off, or spray insecticidal soap as its label directs. Read more

Powdery mildew (Golovinomyces species). A white, dusty coating spreads over leaves in late summer, worst on crowded plants. Space clumps, water at the base and clear badly affected leaves. Read more

Tomato big bud phytoplasma (Candidatus Phytoplasma australasiaticum). Recorded on purple coneflower in Victoria, it turns flowers green and leafy, bunches shoots into a witches' broom and stunts the plant. Leafhoppers such as Orosius argentatus spread it, and nothing reverses it, so remove affected plants.

Sclerotinia rot (Sclerotinia sclerotiorum). A rot of more than 400 host plants, it has been recorded on coneflower in Canada. Stems darken and wilt at soil level, white fungal growth appears, and hard black bodies form on the crown. Lift and bin affected plants, and improve drainage before replanting.

Prevention first

• Grow in full sun and free-draining soil, with room between clumps for air to move.
• Water at the base in the morning, rather than over the leaves.
• Check buds and new stems weekly in spring for aphids.
• Keep weeds down around clumps, because weeds can harbour leafhoppers and the phytoplasmas they carry.

Tips

1. Test ten seeds on damp paper towel in a warm spot, chilling narrow-leaved seed first, to see how many to sow per cell.
2. Mark each clump with a stake, because the plants die back to the ground in winter and are easy to dig into.
3. Plant 'White Swan' and purple coneflower together in generous clumps for a mixed white and purple summer display.