How to Grow White Sage in Australia

White sage (Salvia apiana) is a shrubby perennial of the mint family (Lamiaceae), grown for its silver, aromatic leaves and tall spikes of pale flowers. It grows wild only on dry hillsides in southern California and northern Baja California. It thrives in Mediterranean and inland gardens and struggles in humid ones. It is a different plant from common garden sage (Salvia officinalis) and from clary sage, and its seed is listed as Sage White. Most failures come at germination, from seed buried away from light, and later from watering the plant too kindly.

Three mistakes that matter

1. Burying the seed in cold mix. White sage seed germinates better in light, and seed pushed deep into cool mix often never shows. Press it onto the surface of warm mix and cover it by 2 mm at most.
2. Rich soil and summer watering. Fertile soil that stays damp, or extra water through a hot summer, rots the roots of a plant built for dry hillsides. Plant into lean, sharply drained soil and stop regular watering once the first year is through.
3. A shaded, crowded or humid spot. Shade and still, humid air bring mildew and weak, floppy growth. Give each plant full sun and 1 to 1.5 m of space so air moves through it, and raise the bed in humid districts.

When to plant

The seed germinates at 20 to 30°C, so sow in trays in spring as the days warm, or earlier indoors on a heat mat. Seedlings take six months to a year to reach planting size. Set them in the garden in autumn, never in summer heat.

In the southern zones, plant out around Anzac Day so the roots settle in with the autumn and winter rain. Established plants in dry soil can take about -5°C; where frost is regular, keep young plants in pots under cover through their first winter.

Site, soil and setup

Copy a sunny, stony slope where rain drains away within minutes.

On heavy clay, build the mound or raised bed rather than digging sand into the clay. In cool districts, plant against a north-facing wall or among rocks, where stored warmth and quick drainage help young plants through winter.

Container growing

A pot suits white sage wherever winters are wet, humid or frosty, because the plant can move under cover. Use a pot at least 40 cm wide, which holds about 28 L. A full-sized shrub needs a 50 cm pot of about 52 L. Fill it with cactus and succulent mix, or potting mix with one part coarse sand or perlite to three parts mix.

• Water: deeply when the top 5 cm of mix is dry, and far less in winter; never leave the pot standing in a full saucer.
• Feed: fish and seaweed blend at half strength, 12.5 mL per 9 L, fortnightly through spring only.
• Position: full sun, with the pot raised on feet so it drains freely.

Germinating the seed

White sage seed has no hard coat to break. Part of each seed lot sprouts readily in warmth and light, while the rest stays dormant until a bushfire or time wakes it. Heat and, in some trials, smoke break that dormancy, and light helps too, so surface-sown seed does better than deep-sown seed. Fresh seed often sprouts less well than seed kept dry for a year, because it keeps ripening in storage.

Seed lots often test at about 50 per cent, and untreated seed has peaked at 40 to 70 per cent in different tests. One seed supplier reports only 20 per cent in many sowings. The first seedlings can appear in 4 days and most within 21 days at 20 to 30°C. Sow at least three seeds for every plant you want, which means the whole 15-seed packet for a handful of plants.

Smoke and sandpaper do different jobs. Smoke water carries karrikins, the germination chemicals in smoke that Western Australian scientists identified and named from the Noongar word for smoke. No trial found shows that a fridge chill helps white sage; the one trial that chilled seed after a smoke soak used black sage.

The methods themselves are set out in Soaking, Scarification and Cold Stratification.

When nothing comes up

• Sown too deep. Seed under more than 2 mm of mix sits in the dark; sow again on the surface and press it in.
• Too cold. Below about 18°C germination slows or stalls; move the tray somewhere warmer or onto a seedling heat mat.
• Mix kept wet. Soggy mix rots seed and seedlings; soak the tray once at sowing, then water sparingly.
• Seed too fresh, or stored badly. Fresh seed can hold back until it has dried for months, and seed kept warm and damp loses life, so store packets sealed and cool.
• Given up too soon. Wait six weeks before resowing, and keep the tray, because dormant seed can still come up months later.

Sowing Seeds

Start white sage in trays or cells from treated or untreated seed, because low and uneven germination makes open ground a gamble.

Starting under cover

• Fill cells or a tray with free-draining seed raising mix, adding perlite if it holds water.
• Press two or three seeds onto each cell, or cover them with 2 mm of mix at most, and firm them in.
• Soak the tray from below once after sowing, then water sparingly as the surface dries.
• Keep the tray warm (see When to plant) and bright, under a clear lid lifted daily and removed once seedlings are up.
• Snip extra seedlings at soil level, leaving the strongest one in each cell.
• Pot each seedling into a 5 to 10 cm pot once it has two to four true leaves beyond its seed leaves.

Sowing direct

Direct sowing only makes sense where autumn brings reliable rain and winters are mild, as around Perth and Adelaide. Scatter seed over a raked, weed-free bed just before the autumn rains, press it in with a board without covering it, and expect patchy results. Thin the survivors to 1 to 1.5 m apart.

Transplanting

Harden plants off first (get them used to outdoor sun and wind over about a week), as hardening off seedlings describes. Plant in autumn, 1 to 1.5 m apart, with the top of the root ball level with the soil, and water in well.

Care by growth stage

A young plant needs regular deep drinks to build its roots. An established plant needs almost none.

Over-feeding reduces the essential oils that give white sage its aroma. If growth stalls in very poor sand, a light application of all-purpose controlled release granular (NPK around 14-5-10) scratched in once in spring can help.

Trimming and Shaping

White sage grows new shoots from a woody base, and its tall flower spikes die once flowering is over. Light, regular trims keep it bushy, while hard cuts into bare wood leave gaps that are slow to fill.

• Cut spent flower spikes back to the leafy growth once the seed has dropped or been saved.
• Trim evenly across the top and sides in autumn to keep a rounded shape.
• Take harvest cuts from soft, leafy tips, which shapes the plant as you pick.
• Cut into green, leafy stems, never into bare wood with no leaves.
• Remove dead, broken or rotted stems at their base whenever you see them.
• Replace an old, sprawling plant with one raised from a spring cutting, as Tips describes.

Companion planting

Choose neighbours that want the same hot, dry, lean conditions, and keep thirsty or tender plants well away.

Grows well with

• Thyme, which shares the dry, sunny, free-draining ground and little water.
• Lavender, another dry-climate shrub that suits the same lean, unwatered bed.
• Oregano, which fills the front of a sunny, dry border without crowding the shrub.
• Californian poppy, from the same dry Californian slopes, which flowers between young shrubs.

Keep apart

• Vegetable seedlings, because volatile oils from white sage leaves slowed the root growth of cucumber and oat seedlings in trials.
• Mint and comfrey, which want moist, rich soil and regular water that would rot white sage.
• Other Californian sages, such as black sage, when you plan to save seed, because they cross with white sage.

Harvesting Leaves

Pick leaves once the plant is growing strongly: lightly in the first year, more freely from the second. Spring, before the flower spikes open, is the best time.

• Pick in the morning once the dew has dried, choosing mature, silver leaves.
• Cut whole leafy tips with sharp secateurs, just above a leaf joint.
• Take no more than a third of the plant in one session, and spread the cuts around it.
• Leave some flower spikes standing for the bees and for seed.

Single leaves also dry well spread on a rack until they crumble. Store the dry leaves in airtight, labelled jars in a cool, dark cupboard. The grey dried foliage also suits wreaths and dried arrangements.

Traditional use and history

The species name apiana refers to bees, which crowd the flowers, and the plant is also known as bee sage and sacred sage. Botanists once filed it under other names, among them Audibertia polystachya and Ramona polystachya.

For the Indigenous peoples of southern California and northern Baja California, white sage was food, a household material and a ceremonial plant.

Many Native people speak of white sage as a relative, and its ceremonial use is sacred to them. Traditional harvest took a few leaves at a time, with prayer and thanksgiving, and families who held seed-gathering grounds cared for them over generations.

Beekeepers valued it too: from the mid nineteenth century, American beekeeping guides advised setting hives near white sage. In the mid twentieth century, Native families who moved to cities shared the plant with Native people from other regions. Later, the counterculture of the late twentieth century took up burning it.

A plant under pressure

Demand has outrun the wild supply. Much of the white sage sold in bundles is taken from wild stands, and whole hillsides have been found stripped. Picking plants on public land in California is illegal. About half of its populations have been lost to urban growth, yet it is not listed as endangered or threatened. United Plant Savers places it on its Species At-Risk list, and the Chumash and other California peoples have spoken out against overharvesting. Conservation groups ask people to avoid wild-picked sage and to grow their own.

Safety

White sage 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.

Some relatives are another matter: mintweed (Salvia reflexa) is on NSW WeedWise, and Western Australia prohibits Salvia carduacea and Salvia virgata. Buy seed labelled Salvia apiana, and pull out any self-sown seedlings near bushland.

Common problems

Sudden wilting or winter death. Roots rotting in cold, wet soil are the usual cause (see Three mistakes that matter); move survivors into a raised, gravelly bed or a pot. In warm, wet soil it can be Phytophthora root rot (Phytophthora species), which spreads in soil and water, so replant somewhere better drained. Read more

Leaves greener than expected. New leaves open grey-green and turn white as they age, so a flush of greener growth on a young plant is normal.

Spindly, pale seedlings. Too little light after germination stretches seedlings, so move the tray into full sun or under bright light at once. Read more

No flowers in the first year. Most plants flower from their second year, though some flower in their first in a good season.

Pests and diseases

Established white sage has few serious pests, because its aromatic leaves deter most leaf eaters; trouble mostly comes to seedlings and young plants.

Aphids (Aphididae). Small green or yellow sap-suckers cluster on the soft spring tips of young plants and leave sticky honeydew. Knock them off with a strong jet of water, or spray insecticidal soap at the label rate under the leaves. Read more

Powdery mildew (Oidium and related fungi). A white powdery coating spreads over leaves in humid weather or shade. Water the soil rather than the leaves, remove the worst leaves, and spray 1 part full-cream milk to 10 parts water. Read more

Two-spotted mite (Tetranychus urticae). Tiny mites under the leaves cause fine pale stippling and webbing, worst in hot, dry weather. Hose the undersides, avoid broad-spectrum sprays that kill their predators, and release predatory mites in a bad outbreak. Read more

Damping off (Pythium species and Rhizoctonia solani). Seedlings rot before they emerge or collapse at soil level soon after. Use fresh seed raising mix and clean trays, and water only enough to keep the mix moist. Read more

Prevention first

• Plant in full sun with space around each plant, so leaves dry quickly after rain.
• Water young plants at the base in the morning, never over the leaves.
• Check spring tips for aphids, and leaf undersides for mites in hot spells.
• Ring young plants with a copper-taped collar against snails and slugs.

Tips

1. Save seed in late summer, when it ripens inside the papery flower cups. Rub dry spikes over a sieve and keep the seed sealed in the fridge.
2. Raise new plants from spring cuttings of soft, unflowered shoots, 8 to 10 cm long with the lowest leaves removed. See How to Take Plant Cuttings.
3. Sow a labelled half of the packet treated and half untreated, and note which tray does better with your seed.