How to Grow Catmint in Australia

Catmint (Nepeta racemosa, also listed as Nepeta mussinii) is a low, spreading perennial of the mint family, Lamiaceae, from the Caucasus, Turkey and northern Iran. It is grown for spikes of lavender-blue flowers over grey-green, scented leaves, from late spring into autumn, and bees work it all season. The usual mistake is leaving it to sprawl after the first flush of flowers, when a cut back can bring a second.

Three mistakes that matter

1. Burying the seed. Light helps catmint seed germinate, so seed sown at a normal depth can sit in the tray and never appear. Press it into the surface and cover it no deeper than Starting in trays gives.
2. Wet feet. Root rot thrives in wet soil and is often fatal to catmint. Heavy clay, soggy pots and daily watering kill more plants than dry spells. Plant into free-draining soil and water only when the soil is dry 5 cm down.
3. Skipping the haircut. After the first flush the stems flop open and flowering slows. Shear the plant back as Cutting Back describes, and new growth from the base usually gives a second round of flowers.

When to plant

Catmint seed germinates best with the soil at about 15 to 22°C, so most zones sow in spring and autumn and skip the frosty months. The plants live for several years, so one good sowing is usually enough.

Where frost is regular, start seed under cover about 6 weeks before the last frost and plant out once it has passed. In temperate and Mediterranean gardens, a sowing before Anzac Day gives plants time to settle in before winter.

Site, soil and setup

Catmint comes from dry, sunny, rocky country, so it wants sun and free drainage more than rich soil.

Because it stays put for years, catmint sits outside the vegetable rotation. Grown from this seed it forms a mound about 30 to 45 cm tall and up to about 60 cm wide.

Container growing

The store sells one catmint, and its low habit suits a pot on a sunny patio or courtyard. Use a pot of at least 10 L with drainage holes: a standard 300 mm pot, about 280 mm across inside, holds about 13.5 L. Fill it with a good quality potting mix. Potting and seed-raising mixes can carry Legionella bacteria, so wet them down, wear gloves and a P2 mask, and wash your hands afterwards.

• Water: deeply, by the 5 cm test in Three mistakes that matter.
• Feed: fish and seaweed blend at half strength, about 12.5 mL per 9 L, fortnightly in spring and summer.
• Position: as for a bed, as Site, soil and setup describes.

Sowing Seeds

Catmint does best raised in trays or punnets and planted out once established. The store's Catmint seeds are Nepeta racemosa, the seed-raised species.

Starting in trays

• Fill trays or punnets with moist seed-raising mix.
• Press the seed into the surface and leave it bare or cover it with up to 5 mm of mix (see how deep to sow).
• Keep the mix moist but never wet, in a warm, bright spot.
• Seedlings appear in 7 to 20 days at the soil temperature When to plant gives.
• Once true leaves show, thin crowded seedlings or prick them out into single cells.
• Pinch out the growing tips once seedlings reach 5 to 7 cm, for bushier plants.

Planting out

• Plant out once seedlings have their first true leaves and stand 5 to 10 cm tall.
• Harden them off first (set them outdoors a little longer each day so they adjust to sun and wind) for about a week. See hardening off.
• Space plants 30 to 45 cm apart for a continuous edge, or up to 60 cm for separate mounds.
• Set each plant at the depth it grew in the punnet. Water it in with seaweed solution at half strength, 15 mL per 9 L.
• In spring you can also scatter seed straight into a fine, weed-free bed, press it in and keep it damp. Thin the seedlings to the spacing above.

Care by growth stage

Drainage and restraint decide catmint. It grows in nutrient-poor soil and needs no extra feed in a bed, and over-feeding reduces the essential oils that give it its scent.

Established catmint is drought tolerant and very frost hardy, and it dies back to a low crown in cold winters. If growth stalls in very poor soil, a light scatter of all-purpose controlled release granular (NPK around 14-5-10) can help.

Cutting Back

Cut catmint back to keep the mound compact and to encourage more flowers, lightly through the season and harder as each flush ends.

• Through the season, cut fading spikes just above a set of leaves.
• When the first flush fades, shear the whole plant back by about a third, above the new growth at the base.
• At the end of flowering in autumn, give it a hard cut to keep it bushy.
• In frosty districts, cut the old stems to about 5 to 7 cm and mulch around the crown.
• Divide a crowded clump in spring or autumn (see dividing perennials).

Companion planting

Catmint belongs with other sun-lovers that like the same lean, well-drained soil, and its long flowering draws bees into nearby beds.

Grows well with

• Lavender, which wants the same full sun and lean, free-draining soil.
• Thyme, another low perennial kept compact by lean soil and a trim after flowering.
• Roses, whose bare lower stems catmint carpets with flowers.
• Fruiting vegetables and fruit trees, where the bees it draws help with pollination.

Keep apart

• Mint, whose runners crowd a low plant and which wants rich, moist soil.
• Thirsty leafy crops watered every day, where the wet soil invites root rot.

Harvesting Flowers and Foliage

Cut stems for drying once the spikes are in flower, from the first flowering and again after each cut back.

• Pick in the morning, once dew has dried.
• Cut the top third of flowering stems, taking up to a third of the plant at once.
• Tie small bunches and hang them in a shady, airy spot out of direct sun.
• They are dry, usually in about 10 days, when the leaves are brittle and the petals papery.

Strip the dry leaves and flowers into clear glass jars with tight lids, and keep them in a dark cupboard. If moisture beads inside a jar, dry the herbs a little longer. Home-dried herbs usually keep their quality for about 12 months.

Stuff dried flowers and leaves into cat toys, or add them to potpourri. Not every cat responds, and some become aggressive, so supervise cats around the plant and its toys.

Common problems

Seed does not come up. Seed buried too deep or sown into soil outside the range When to plant gives may never appear; see Three mistakes that matter. Read more

Leggy plants with few flowers. Too much shade stretches the stems and cuts flowering, so move plants into the full sun Site, soil and setup gives.

Plants flattened by cats. Cats chew catmint, lick it and roll in it, which can crush young plants; protect them with a low wire fence until they fill out. Read more

Pests and diseases

Sap-suckers and wet roots cause most trouble on catmint; before using any spray, read its label and use it only as directed.

Aphids (family Aphididae). Small sap-suckers cluster on new shoots and under leaves, leaving wilted, discoloured growth and sticky honeydew. Hose them off, use a soap spray, and encourage the predatory insects that eat them. Read more

Two-spotted mite (Tetranychus urticae). Leaves turn dry, mottled and pale, with a sandpapery feel underneath, and numbers build fastest in hot, dry weather. Prune for airflow and spray leaf undersides with a soap spray. Read more

Whitefly (family Aleyrodidae). Tiny white insects cluster under the leaves and rise in a cloud when disturbed, and leaves yellow. Hose them off, or spray insecticidal soap under the leaves. Read more

Root rot (soil-borne fungi). Plants yellow and wilt, and the stem base and roots turn soft and brown in wet soil. It is often fatal, so remove affected plants and fix the drainage before replanting. Read more

Prevention first

• Plant into free-draining soil, and keep mulch from touching the stems.
• Water at the base in the early morning or late afternoon, keeping the leaves dry.
• Make compost, mulch the soil and avoid broad insecticide sprays, so predatory mites and insects stay.
• Hang yellow sticky traps early in the season to catch the first winged aphids and whitefly.

Tips

1. Plant catmint beside a path or step, where brushing past releases its soft minty scent.
2. For a sea of blue on a sunny bank, plant several seedlings at the closer spacing Planting out gives.
3. To copy a favourite plant exactly, take softwood cuttings in early summer (see how to take cuttings).