How to Grow Clary Sage in Australia

Clary sage (Salvia sclarea) is a biennial herb of the mint family, Lamiaceae, grown for its large, hairy, aromatic leaves and its tall flower spikes. In its second year the spikes open in pink, lilac and white bracts that bees crowd around. It is far bigger than common sage, which has its own Sage guide. The usual mistake is burying the seed, which needs light to germinate.

Three mistakes that matter

1. Burying the seed. Seed sown deep under soil often fails to come up, because it needs light to germinate. Press it firmly onto moist mix and barely cover it, as Sowing Seeds describes, then keep the surface damp until seedlings show.
2. Growing it rich and wet. Rich, heavily fed soil gives tall, floppy plants with few flowers, and soil that stays wet through winter can rot the crown. Grow it lean, in full sun and free-draining soil, and feed with a light hand.
3. Giving up on it in the first year. A first-year plant is only a low rosette of leaves, and the flower spikes come in its second year. Pick leaves meanwhile, and leave the plant in place through winter so it can flower.

When to plant

Clary sage germinates best with the soil at about 19 to 21°C, so most zones sow in spring as the soil warms.

In Canberra, Ballarat and the tablelands, start seed in a tray under cover and plant out once frosts ease, around Melbourne Cup weekend. For an early start anywhere, a seedling heat mat warms the tray from below.

Site, soil and setup

Clary sage comes from the northern Mediterranean, and it does best on light, sandy or gravelly soil in full sun.

A plant holds its spot for two years, so keep it out of the vegetable rotation, at the back of a herb or flower bed. On heavy clay, read waterlogged soil before planting.

Container growing

A large pot suits clary sage where garden soil is heavy or stays wet. Choose a pot 40 cm or more across the rim; a standard 400 mm pot holds about 28 L of mix. Fill it with premium potting mix and add a few handfuls of coarse sand or grit. The store sells one clary sage, with no compact form.

• Water: when the top few centimetres of mix feel dry, then soak until water runs from the drainage holes.
• Feed: fish and seaweed blend at half strength, about 12.5 mL per 9 L, fortnightly from spring to late summer.
• Position: full sun, sheltered from strong wind, which can topple the flower stems of a top-heavy pot.

Sowing Seeds

Start the seed in a tray, where young seedlings can be guarded from snails, or sow direct once the soil is warm. The store's Clary Sage seeds are Salvia sclarea.

Starting in a tray

• Fill a tray or cell punnet with moist seed-raising mix and sow the seed thinly.
• Press the seed firmly onto the surface and barely cover it, so light still reaches it.
• Keep the mix damp and the tray in bright light out of direct sun, at the soil temperature When to plant gives.
• Seedlings usually emerge in 1 to 3 weeks.
• Move seedlings into their own pots once they can be handled.

Sowing direct

• Rake a sunny, weed-free spot to a fine surface.
• Sow thinly, press the seed in and barely cover it.
• Keep the surface damp with a fine spray until seedlings appear.
• Thin seedlings in stages to 60 to 90 cm apart.

Planting out

Plant tray-raised seedlings out when they are 5 to 10 cm tall. Harden them off first (set them outside a little longer each day, for a week or two, so they adjust to sun and wind). Water them in with seaweed solution at half strength, 15 mL per 9 L.

Care by growth stage

Once established, clary sage tolerates drought far better than wet soil or heavy feeding. Over-feeding reduces the essential oils that give clary sage its flavour and aroma.

If growth stalls in very poor soil, scratch in all-purpose controlled release granular (NPK around 14-5-10) once in spring, at half the label rate. Established plants are frost hardy.

Cutting Back

Cutting back keeps the plant tidy and decides whether it self-seeds. As a biennial, clary sage usually dies once it has flowered and set seed.

• In the first year, pick the outer leaves and leave the centre of the rosette to grow.
• Remove yellowing or damaged lower leaves so air moves around the crown.
• As the flowers fade, cut the stalks back to near the ground for a second flush of growth and flowers.
• Cut spent spikes before the seed drops wherever self-sown seedlings are not wanted.
• For seed, let one spike dry on the plant, cut it once the seed cases turn brown, and finish drying it in a paper bag.
• Store the seed only once it is fully dry, in a labelled jar in a cool, dark place.

Companion planting

Clary sage suits a sunny, dry herb or cottage bed, where its flowers bring bees to the plants around it.

Grows well with

• Thyme and Oregano, low herbs that want the same sun and sharp drainage.
• Rosemary and Lavender, which share its liking for dry, lean soil.
• Yarrow and Calendula, which also draw beneficial insects to the bed.

Keep apart

• Mint, which needs moist soil and can overrun a bed.
• Thirsty, heavily fed vegetables, whose watering and feeding keep its roots too wet and its growth soft.

Harvesting Leaves and Flowers

Pick leaves once the rosette is well formed, about 11 to 16 weeks after sowing. Cut flower stems in the second year once the spike is well formed and the bracts have coloured, before it starts to fade.

• Cut single leaves with scissors rather than tearing them.
• Pick sparingly, a few leaves from each plant at a time.
• Harvest in the morning, once any dew has dried.
• Keep watering steady through picking, as for the last care stage.

To dry leaves or flower stems, hang small bunches in a shaded, airy place; in good weather they dry in about 10 days. Leaves are ready when they are brittle but do not shatter. Store them in airtight glass jars in a dark cupboard, where they keep for about 12 months, and dry them longer if condensation forms inside.

Historically, cooks used the leaves in omelettes and fritters, the plant flavoured wine and beer, and the flowers went into salads and garnishes.

Common problems

No seedlings after three weeks. Seed buried too deeply, sown into cold soil or allowed to dry out often fails; see Three mistakes that matter. Read more

Tall, floppy seedlings. Seedlings stretch towards the light when a tray sits in shade, so move them into bright light as soon as they emerge. Read more

Plant collapses at the base. Wet soil rots the crown, as Three mistakes that matter warns. Replant on a mound or in a gritty pot, and keep mulch clear of the stem.

Plant dies after flowering. A plant that dies after setting seed in its second summer has finished its biennial life cycle, so let a spike self-seed or sow again. Read more

Pests and diseases

Clary sage has few serious problems, and most damage falls on young seedlings.

Slugs and snails, including garden snail (Cornu aspersum). They feed at night and after rain and can chew young seedlings to the ground. Search with a torch about two hours after sunset, or guard seedlings with an iron-based snail bait or a copper band around pots. Read more

Damping off (Pythium species and Rhizoctonia solani). Seedlings rot at soil level and topple over, most often in wet, crowded trays. Sow thinly into fresh mix and avoid overwatering. Read more

Aphids (Aphididae). Small green or yellow sap-suckers crowd onto soft new leaves and flower spikes and leave them sticky. Squash small groups or knock them off with a strong jet of water. Read more

Powdery mildew (Erysiphales). White, powdery patches spread over the leaves in humid weather, most often in crowded or shaded beds. At the first patches, spray 1 part full-cream milk to 10 parts water in the early morning, and repeat after rain. Read more

Prevention first

• Sow in fresh seed-raising mix, in clean trays.
• Set citrus rind halves near seedlings and collect the snails sheltering under them.
• Give plants their full spacing so air moves freely between them.
• Water the soil at the base of the plant, not the leaves.

Tips

1. Plant it beside a path, where brushing past the leaves releases their strong, musky scent.
2. Sow a few seeds in each of two years running, so one plant is usually in leaf while another flowers.
3. Clary sage is not a declared weed in any Australian state or in the Northern Territory. It does self-seed, so check your council's weed list before letting it spread near bushland.