How to Grow Catnip in Australia

Catnip (Nepeta cataria) is a short-lived perennial of the mint family, Lamiaceae. It is grown for its downy, grey-green leaves, which many cats respond to, and for white flower spikes that bees visit. It asks for little more than sun and free-draining soil, though humid tropical summers rarely suit it. The usual mistake is leaving seedlings where cats can reach them.

Three mistakes that matter

1. Leaving young plants open to cats. Cats roll on catnip, rub against it and chew it, and can snap the stems of a small plant or destroy it. Cover seedlings with a chicken wire cage or a mesh cloche until they are well established, or grow them in a hanging basket.
2. Keeping the soil wet. Catnip prefers dryish, fast-draining soil, and roots that stay wet can rot and kill the plant. Once plants are established, water only when the soil is dry about 5 cm down, and on clay, plant on a raised mound or bed.
3. Letting every flower spike set seed. Catnip self-seeds freely, can become invasive and may be an environmental weed in your area, so check with your council before planting near bushland. Cut the spikes as they fade, as Cutting Back describes.

When to plant

Catnip seed germinates best in soil at 20 to 25°C, though seedlings can appear from about 16°C. Most zones sow in spring and again in early autumn. One sowing gives plants for a few years, and self-sown seedlings often replace them.

In the tropics, the dry season is the only reliable window.

Site, soil and setup

In the wild, catnip grows on dry banks, roadsides and field edges, so it wants sun, free drainage and soil that is not too rich.

Because it stays put for years, catnip sits outside the vegetable rotation. See soil pH explained before liming.

Container growing

Catnip grows well in a pot, and a hanging basket keeps it out of reach of cats. Use a pot that holds at least 10 L: a standard 300 mm pot, 28 cm across inside, holds about 13.5 L. Fill it with a premium potting mix and do not stand the pot in a saucer. The store sells one catnip with no named compact form, so trim plants to keep them in scale.

• Water: often in hot weather, letting the mix dry a little between waterings but never dry out completely.
• 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

Raise catnip in trays and plant it out, or scatter the seed on a prepared bed. The store's Catnip seeds are true catnip, Nepeta cataria.

Starting in trays

• Press the seed onto seed-raising mix and barely cover it, 5 mm at most, as it needs light (see how deep to sow).
• Keep the mix moist but never wet; seedlings appear in 7 to 20 days at the soil temperature When to plant gives.
• Prick seedlings out into single cells once they can be handled.
• Harden off the young plants (set them outdoors a little longer each day so they adjust to sun and wind) for about a week.
• Plant them out at 5 to 10 cm tall, 40 to 60 cm apart.
• Water them in with seaweed solution at half strength, 15 mL per 9 L.

Sowing direct

• Rake the bed fine after the last frost, scatter the seed thinly and tamp it onto the surface.
• Keep the surface damp until seedlings appear.
• Thin the seedlings in stages to 40 to 60 cm apart.
• Lay chicken wire over the bed until the plants establish, as Three mistakes that matter explains.

Care by growth stage

Drainage decides how well catnip grows. Once established it is drought tolerant and needs water mainly in long dry spells. It grows in nutrient-poor soil and needs no regular feed in a garden bed, so keep any feeding at half strength.

Established catnip is frost hardy and may die back in a cold winter, then reshoot in spring. 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

Regular cutting keeps catnip bushy and leafy and, as Three mistakes that matter explains, stops it seeding through the garden.

• Pinch out the stem tips as young plants grow, so they branch.
• Cut flower spikes as they fade, just above a pair of leaves, before the seed ripens.
• Cut the whole plant back after its first flowering to bring on a second flush of leaves and flowers.
• Cut stems to just above the ground in late autumn, or clear dead growth when new leaves appear in spring.
• Divide a crowded clump in spring (see dividing perennials).
• Pull stray seedlings while they are small.

Companion planting

Catnip draws bees and butterflies and is said to repel some pests.

Grows well with

• Lavender, which wants the same full sun and free-draining soil.
• Thyme, another perennial for lean, sharply drained soil and little water.
• Cabbage and other brassicas, since catnip is said to repel aphids and to attract lacewings, which eat them.

Keep apart

• Mint, which wants rich, moist soil and spreads by runners.
• Freshly sown beds, where cats drawn to the catnip may dig in the soft soil.

Harvesting Leaves and Flowers

Start picking leaves once plants are established, usually 11 to 12 weeks after sowing, and take them before the flowers form.

• Pick in the morning, once the dew has dried.
• Snip single leaves or whole stem tips just above a pair of leaves.
• For drying, cut whole stems with their flowers close to the ground.
• Hang them upside down in small bunches somewhere dry, airy and out of the sun.
• Once crisp, strip the leaves and flowers into an airtight jar and keep it in the dark.

Dried leaves keep their fragrance, so they suit cat toys and pot-pourri. The store sells catnip as seed for garden growing, not as a food, a tea or a medicine.

Common problems

Seed slow or patchy to come up. Catnip seed can be slow and uneven to come up, so keep the mix moist for at least 20 days before resowing. Read more

Cats show no interest. Not every cat responds, and kittens under about six months usually do not. An unbruised plant gives off little scent, so crush a leaf to test.

Large, sprawling plants. Rich, moist soil grows a big, loose plant, so keep feeding light and pinch the tips as Cutting Back describes.

White powder on the leaves. Powdery mildew can appear in long spells of very humid weather, so give plants room and water at the base. Read more

Plants fading after a few years. Catnip is short-lived, so keep a few self-sown seedlings or divide the clump to replace old plants.

Pests and diseases

Sap-sucking pests cause most trouble on catnip in warm weather; before using any spray, read its label and use it only as directed.

Aphids (family Aphididae). Small green or yellow sap suckers cluster on new shoots and under the leaves, leaving sticky honeydew. Knock them off with a jet of water or spray insecticidal soap under the leaves. Read more

Two-spotted mite (Tetranychus urticae). Tiny mites under the leaves leave yellow, stippled patches and multiply fast in hot, dry weather. Hose the leaf undersides and avoid broad-spectrum sprays, which kill the mites' predators. Read more

Whitefly, greenhouse whitefly (Trialeurodes vaporariorum) or silverleaf whitefly (Bemisia tabaci). Tiny white insects rise in a cloud from the leaf undersides and can yellow and weaken the plant. Hose them off, hang yellow sticky traps and spray insecticidal soap under the leaves. Read more

Damping off (Pythium species and Rhizoctonia solani). Seedlings rot at soil level and fall over, most often in wet mix. Sow thinly in clean seed-raising mix and avoid overwatering. Read more

Prevention first

• Sow in fresh seed-raising mix, with clean trays and tools.
• Check shoot tips and leaf undersides weekly in warm weather.
• Encourage ladybirds and lacewings, which feed on aphids and mites.
• Water at the base, early in the day, so the leaves stay dry.

Tips

1. Sew a handful of dried leaves into a small cloth bag for a cat toy.
2. Take softwood cuttings early in the growing season; they strike well in propagating mix (see how to take cuttings).
3. Wear gloves when working soil that cats visit, because cat droppings can carry Toxoplasma.
4. To save seed, let a single spike ripen, rub out the seed and sow it in your zone's window in When to plant.