How to Grow Lavender in Australia

English lavender (Lavandula angustifolia) is a small evergreen shrub in the mint family, Lamiaceae, grown for its scented flower spikes and grey, aromatic leaves. It suits the dry summers of southern Australia, from Tasmanian farms to the hills around Daylesford in Victoria. Its flowers bring bees to the garden. Plants most often die for one reason: their roots sit in soil that stays wet.

Three mistakes that matter

1. Planting where water lies. Lavender roots rot in heavy soil that stays wet, and a plant can decline for a season or two before it dies. Plant on a mound or raised bed (see Site, soil and setup) or in a pot.
2. Sowing without a chill, or too deep. Seed sown straight from the packet, or buried, often comes up thin and patchy. Sow it on the surface, then give the pot a spell in the fridge, as Sowing Seeds shows.
3. Cutting into bare wood. Old, leafless stems seldom reshoot, so a hard cut can leave a bare, split bush. Trim every year after flowering, keeping to green growth, as Trimming and Shaping describes.

When to plant

Lavender seed sprouts best at about 21°C, so sow in the mild weather of autumn or spring, once the seed has had its cold chill. A well-kept plant can live 10 to 15 years, so one sowing lasts a long time.

In frosty gardens, keep autumn sowings under cover and plant them out in spring, because young plants rot in cold, wet soil.

Site, soil and setup

Give lavender the sunniest, most open spot you have, with air moving freely around it. Lean, gravelly ground suits it better than rich vegie-bed soil.

Container growing

A pot lets you control drainage, which makes it the safest choice in humid or heavy-soil gardens. Use one with drainage holes, at least 30 cm wide, about 14 L. True lavender suits a 40 cm pot, about 28 L. 'Munstead' is the compact choice; Sowing Seeds gives its size. Fill the pot with quality potting mix and add coarse grit, up to a quarter of the volume.

• Water: deeply once or twice a week in hot, dry spells, and keep the mix fairly dry in winter.
• Feed: seaweed solution at half strength, 15 mL per 9 L, fortnightly in spring only.
• Position: full sun, moved against a wall or under eaves to keep off long spells of rain.
• Repotting: move up a size each spring, into fresh mix.

Sowing Seeds

Start lavender in small pots or trays, because the seed is slow and direct sowing seldom succeeds.

Preparing the seed

Lavender seed needs cold stratification (a spell of cold, moist conditions that breaks dormancy) before it sprouts well. Sow it as below, then seal the pot in a plastic bag and keep it in the fridge for 2 to 4 weeks. Then open the bag and let the pot warm to room temperature for a few days. The article on seed treatments compares the methods.

Starting in pots

• Press the seed onto moist seed raising mix in a small pot. Barely cover it, 3 mm at most, because it germinates better close to the light.
• After chilling, keep the pot in a bright spot at the temperature in When to plant, using a seedling heat mat if needed. Water from below.
• Expect seedlings in 14 to 28 days, with stragglers appearing for weeks after.
• Prick out (lift and move) each seedling into its own small pot once it is large enough to handle.
• Grow them on in bright light for three months or more, until roots fill the pot.

Seed-grown English lavender does not come true, so plants vary in height, colour and flowering time. That is why commercial growers raise their plants from cuttings. French lavender (Lavandula dentata) and Italian or Spanish lavender (Lavandula stoechas) are separate species outside this seed range. L. stoechas is a declared noxious weed in Victoria and can turn weedy elsewhere, so check your council's weed list before planting it.

Planting out

• Harden off (gradually accustom seedlings to sun and wind) over a week or so, as hardening off seedlings describes.
• Plant at the depth the seedling grew in its pot, on a mound in heavy soil, at the spacing in the table above.
• Water in well, then water regularly through the first summer.

Care by growth stage

Restraint decides the crop: too much water or fertiliser gives soft, leafy plants with fewer flowers and a higher risk of rot.

Keep weeds out of the root zone in the first year, because young lavender competes poorly with them. If growth stalls in very poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched in each spring can help.

Trimming and Shaping

A trim every year, straight after flowering, keeps the bush dense and slows the centre turning woody.

• Young plants: pinch off flower spikes in the first year so the plant branches.
• After flowering: cut back by about a third, taking the spent stalks and a little leafy growth.
• Where to cut: just below a pair of leafy side shoots, with secateurs, or with shears for a hedge.
• Green wood only: leave at least 4 cm of green leaves on every stem.
• Spring tidy: clip off frost-damaged or untidy tips once new growth starts.
• Old plants: replace straggly, woody bushes with young plants rather than cutting them hard.

Companion planting

Lavender belongs with plants that like the same dry, lean conditions.

Grows well with

• Salvias, gaillardia and echinacea, which share its low water needs.
• Fruit trees and the vegie patch, where bees drawn to the lavender also work the crop flowers.

Keep apart

• Mint, which needs constant moisture and sends runners through its neighbours.
• Beds on frequent sprinklers, such as lawns and leafy vegies, which keep the soil too wet.
• Tall shrubs that shade it, since lavender leans and sprawls toward the light.

Harvesting Flower Stems

Pick when about half the flowers on a spike are open, or when the first flowers open if the stems are for drying.

• Cut in the morning, once the dew has dried and before the heat.
• Skip picking after rain or after watering overhead the night before.
• Cut the stems as long as possible, above the leafy growth.
• Gather bunches of 50 to 100 stems with a rubber band, which tightens as the stems shrink.
• Hang the bunches upside down in a dark, dry, airy place.

Once dry, strip the buds and keep them in a sealed, dark container somewhere cool, because light and air shorten their life. Dried flower heads keep their scent for months.

English lavender is the type used in cooking, and its buds flavour baking and teas. Dried flowers also fill sachets for drawers and the linen cupboard.

Common problems

Seedlings keep appearing for weeks. Lavender germinates slowly and unevenly, so keep the pot moist; if nothing more comes up, chill it again for 2 to 4 weeks. Read more

Plants differ in height or colour. Seed-grown English lavender varies from plant to plant, and Tips shows how to make a matching row.

Lanky, open plants with few flowers. Shade, rich soil or too much fertiliser pushes leaf at the expense of flowers.

Sections dying back in humid summers. Heat with humidity kills parts of English lavender bushes in subtropical gardens, where a pot is the safest choice; see Container growing.

Pests and diseases

In dry conditions lavender has few pest or disease problems.

Root rot (Phytophthora species). These soil-borne water moulds attack roots in wet, heavy ground, and a plant may die a section at a time over a year or two. Infected plants cannot be saved, so remove them, clean tools and boots afterwards, and fix the drainage.

Damping off (Pythium water moulds and soil fungi). Seedlings collapse at the base, one after another, most often in overwatered mix. Read more

Two-spotted mite (Tetranychus urticae). These mites, under 0.5 mm long, feed under the leaves and leave yellow stippling, and numbers climb fast in hot, dry weather. Read more

Prevention first

• Grow on a mound, raised bed or pot, and water the soil rather than the leaves.
• Sow into fresh seed raising mix in clean pots, and water seedlings in the morning.
• Space plants so air moves between them, and trim them after flowering.
• Check leaf undersides in hot, dry spells, and avoid broad sprays that kill the ladybirds and predatory mites that eat mites.

Tips

1. For a matching hedge, choose the best seedling and grow more from it by cuttings, which copy the parent exactly; taking cuttings shows how.
2. Plant 'Munstead' beside a path, where brushing past the leaves releases their scent.
3. Keep the prunings: once dry, their oil makes them handy firelighters.
4. In Tasmanian gardens, wallabies and pademelons generally leave lavender alone, although they may shelter under large bushes.