Lavender is one of the most requested plants in the country and one of the most frequently killed. The plant is not difficult; the problem is that most Australian gardens offer it the opposite of what it evolved for. Get the species right for your climate, give it sharp drainage and prune it before it goes woody, and you get silver foliage all year and flowers that hum with bees for months.
Quick facts
| Detail | Specification |
|---|---|
| Botanical name | Lavandula species and hybrids |
| Mature size | 40cm to 1.5m tall and wide, depending on species |
| Position | Full sun, at least six hours, open and airy |
| Soil | Sharply drained, gritty or sandy, pH 6.5 to 7.5 |
| Water | Weekly through the first summer, then rarely |
| Climate zones | English types in cool temperate; French and Allardii types in warm temperate and subtropical |
| Flowering | Spring into summer, with repeat flushes in warm districts |
Choosing the right lavender
The four groups sold in Australia are not interchangeable, and picking the wrong one is the most common reason lavender fails here.
English lavender (Lavandula angustifolia) is the perfumery species, growing 60 to 80cm with the classic narrow spikes and the strongest scent. It needs cool nights and low summer humidity, which makes it excellent in Melbourne, the Adelaide Hills, Canberra, Tasmania and the Southern Highlands, and unreliable in Brisbane. Asa Blue is a compact deep-violet form, and English Pink gives the same habit in soft pink.
French lavender (Lavandula dentata) has toothed grey-green leaves and softer mauve flowers topped by small bracts. It is far more tolerant of humidity and warmth than any other species, flowers almost year-round in warm districts, and reaches about 1 to 1.2m. If you garden north of Coffs Harbour, start with French lavender or the white-flowered French White.
Italian or Spanish lavender (Lavandula stoechas) carries the showy rabbit-ear bracts and flowers earliest of all, from late winter. Forms such as Avonview reach 80cm to 1m and cope with warmth better than English types. The species has naturalised in parts of Victoria and South Australia, so check your local council's declared plant list before planting in a rural setting.
Allardii types (Lavandula x allardii) are hybrids of dentata and latifolia, and they are the workhorses. Mt Lofty lavender grows to about 1.2 to 1.5m with long stems, tolerates both heat and humidity, and makes an informal low hedge where the smaller species would sulk.
How to plant
Position. Full sun and moving air. A lavender shaded by a shrub for half the day will be thin, leggy and prone to fungal problems. Slopes, driveway edges and raised beds all suit it.
Soil. Drainage matters more than fertility. On clay, do not dig a hole and fill it with compost, because that creates a sump. Build a mound 20 to 30cm high and 60cm across from a coarse gritty mix and plant into that. Lavender prefers neutral to slightly alkaline soil, so if your pH sits below 6, work in a handful of dolomite per plant.
Spacing. Allow 60 to 90cm between plants for the larger species and 40 to 50cm for a low informal hedge of English types. Crowding restricts airflow and invites the fungal problems below.
Mulch. Use gravel or crushed rock rather than bark or sugar cane. Organic mulch holds moisture against the crown, which is what kills lavender. Keep it 50mm clear of the stems.
Watering in. Soak once at planting, then water weekly for the first summer only. After that, established plants need no supplementary water except in extended drought, which is why lavender belongs with the picks in our guide to drought tolerant plants.
Ongoing care
Watering
Under-water rather than over-water. Once the plant has been in the ground a year, a deep soak once a month through a hot dry summer is generous. Overhead sprinklers are the enemy, because wet foliage in humid weather leads straight to botrytis. Use drippers at the base and water in the morning.
Feeding
Lavender flowers best on lean soil. One light application of complete fertiliser in early spring is all it needs, and even that is optional in reasonable ground. Heavy nitrogen produces soft, floppy growth, delays flowering and reduces the concentration of aromatic oils that make the plant worth growing.
Pruning
This is the rule that decides everything. Lavender will not reshoot from bare grey wood. Cut back by roughly a third as soon as each flush of flowers fades, always finishing above green leaves, and never cut into the leafless base. Two light prunes a year, typically after the main spring flush and again in early autumn, keep the bush dense and domed. A plant left unpruned for two seasons splits open in the middle and cannot be repaired, which is when most people conclude that lavender is short-lived.
Common problems and fixes
Sudden collapse in warm humid weather. Root and crown rot, usually Phytophthora, and it is fatal. Prevention is the only cure: mounded planting, gravel mulch, no summer irrigation and generous spacing.
Grey furry mould on flowers and stems. Botrytis after a wet spell. Cut out affected growth, thin the plant to open it up and stop overhead watering.
Frothy white spittle on stems. Spittlebug nymphs, cosmetic rather than damaging. Hose them off if they bother you.
Yellow mottled leaves and twisted growth. Alfalfa mosaic virus is common in lavender and has no treatment. Remove the plant and do not propagate from it.
Woody, open centre with flowers only at the tips. Age plus missed pruning. Take soft-tip cuttings in autumn and replace the parent plant rather than cutting it back hard.
Frequently asked questions
Which lavender grows best in humid climates?
Lavandula dentata, sold as French lavender, is by a wide margin the most humidity-tolerant species and the sensible default for Brisbane, the Gold Coast and coastal northern New South Wales. Lavandula x allardii is the next best. English lavender, Lavandula angustifolia, needs cool nights and rots quickly in a warm humid summer.
Why did my lavender die suddenly in summer?
Almost always root rot rather than heat. Lavender evolved on stony Mediterranean hillsides and cannot tolerate wet feet, so a single week of warm humid weather on heavy soil can kill an established plant. Raised mounds, coarse gravel mulch and no irrigation once established are the fixes, and our guide to understanding root rot explains what is happening below ground.
How do you prune lavender so it lasts?
Cut back by about one third immediately after each flowering flush, always leaving green leaves below the cut. Lavender will not reshoot from bare grey wood, so once you cut into the woody base that stem is finished. Two light prunes a year keep the plant tight for far longer than one hard one.
Does lavender need fertiliser?
Very little. Rich soil and heavy nitrogen produce soft leafy growth, fewer flowers and less aromatic oil. A light dressing of complete fertiliser in early spring is plenty, and on acid soils a handful of dolomite or garden lime to lift the pH towards neutral does more good than feeding.
How long does a lavender plant live?
Expect five to eight years from English and Italian types in a suitable climate, and three to five years from French lavender in the subtropics. They become woody and open in the middle with age. Rather than trying to rejuvenate a bare plant, take cuttings in autumn and replace it.
Can lavender grow in pots?
Yes, and pots are the best answer on heavy clay or in humid districts. Use a 30 to 40cm container with drainage holes, a free-draining mix rather than a moisture-retaining one, and terracotta if you can, because it dries the root ball between waterings. Never sit the pot in a saucer.
Ready to plant?
Lavender earns its place three times over: silver foliage through winter, months of flowers, and a scent that carries across the garden, which is why it appears so often in our roundup of the most fragrant plants for Australian gardens. It also holds a clipped line beautifully along a path, alongside the options in our guide to the perfect edging plants, and it sits happily among the low maintenance plants that thrive in full sun. Browse the full lavender range within our fragrant plants collection, or start with a hardy French lavender if humidity is your main obstacle.
