How to Grow Lemon Mint in Australia

Lemon mint (Monarda citriodora) is an annual of the mint family, Lamiaceae. It is grown for its tiered whorls of pink to purple flowers and its lemon-scented leaves. It is also sold as lemon bee balm or lemon bergamot, but it is neither a true mint nor lemon balm. Bees work the flowers for weeks. It goes wrong most easily at sowing, when the tiny seed is buried too deep to see the light it needs.

Three mistakes that matter

1. Covering the seed. Lemon mint seed needs light to germinate, and seed buried under soil may never come up. Press it onto the surface of moist mix and leave it uncovered, as Sowing Seeds describes.
2. Sowing into cold soil. The plant is frost tender and the seed waits for warmth, so an early sowing sits idle or is lost to frost. Wait until frosts are over and the soil has warmed, as When to plant explains.
3. Growing it like a vegetable. Rich soil, heavy feeding and constant watering give soft, floppy stems, and wet ground rots the roots. Choose lean, well-drained soil, and water only as Care by growth stage sets out.

When to plant

Sow once the last frost has passed and the soil holds 16°C to 22°C. In that range seed usually emerges in 10 to 21 days. Under cover, start seed 6 to 9 weeks before the last frost is expected. One sowing a season is enough, and plants often self-sow for the next year.

At the early edge of a window, sow under cover rather than outdoors. At the late edge, sow promptly, because the first frost kills the plant and a late sowing has less time to flower.

Site, soil and setup

This is a wildflower of dry American prairies and roadsides, and it grows best on a little neglect.

Container growing

Lemon mint grows well in a pot on a sunny balcony or where frost comes early. Use a pot with drainage holes, at least 30 cm across and holding about 10 to 15 L of quality potting mix. Grow one plant in it. Sow lemon mint seed on the surface of the pot or plant a seedling. Allow for a plant of 60 to 90 cm.

• Water: when the surface of the mix feels dry, and check daily in hot weather. See watering pots in summer.
• Feed: fish and seaweed blend at half strength, about 12 mL per 9 L, fortnightly from first flowers.
• Position: full sun, with air moving around the pot.
• Handling mix: potting mix can carry Legionella bacteria, so dampen it first, wear gloves and a P2 mask, and wash your hands afterwards.

Sowing Seeds

Start lemon mint from seed, either in trays for an early start or direct into the bed once the soil is warm.

Starting under cover

• Fill a tray with moist seed-raising mix and firm it level.
• Scatter the seed thinly over the surface and press it in. At about 2,000 seeds to the gram, mixing it with dry sand helps spread it, as sowing tiny seeds shows.
• Do not cover it. Mist to keep the surface damp, and keep the tray bright and at the warmth When to plant gives.
• Prick out seedlings into small pots once they can be handled.

Sowing direct

Rake the bed fine, water it, then scatter the seed and press it into the surface with a board. Keep it damp until seedlings appear. Thin in stages to 30 to 45 cm apart, moving the spare seedlings elsewhere.

Planting out

Plant out after the last frost, when seedlings are 5 to 10 cm tall. Harden them off first (get them used to outdoor sun and wind a little more each day) for about a week. Hardening off seedlings covers the method. Set them 30 to 45 cm apart and water them in.

Care by growth stage

Restraint decides this crop: in the ground, water until plants are about 30 cm tall, then only in long dry spells.

If growth stalls in very poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched into the surface can help.

Deadheading

Cutting off fading whorls keeps new flowers coming for longer.

• Cut each stem back to the next pair of leaves as its top whorls fade.
• Cut flowers for the vase often, which does the same job.
• From late summer, leave a few stems in a spare corner to ripen seed. Plants self-sow freely, so cut the rest before seed drops.
• After the first frost, pull the plants and compost any free of mildew.

Companion planting

Lemon mint is a bee plant first, so it earns a place beside crops that need pollinating.

Grows well with

• Pumpkins and zucchini, which set fruit poorly when too few bees visit.
• Oregano, a mint-family herb that shares its need for sun and well-drained soil.
• Alyssum and yarrow, which draw in the predators of aphids.

Keep apart

• Mint, which spreads by creeping runners and wants moist soil.
• Tall crops such as sweet corn and sunflowers, which shade a plant that flowers best in full sun.

Harvesting Leaves and Flowers

Flowers usually open 12 to 17 weeks from sowing; cut them for the vase as the whorls colour and begin to open.

• Pick leaves as needed once plants are growing strongly, taking young leaves for the brightest lemon scent.
• Cut flower stems in the cool of the day and stand them in water straight away.
• Strip any leaves that would sit below the water line.
• For drying, cut stems with the whorls fully open and hang them in bunches somewhere dry and airy.
• For seed, cut heads once they are dry and brown, then shake the seed into a paper bag.

Chop fresh leaves into ice cube trays to keep them. Once dried leaves are brittle, store them and the seed in airtight jars away from light, and dry them longer if condensation forms.

The leaves flavour salads, fish and chicken dishes and herbal teas, and the flowers make an edible garnish.

Common problems

Seedlings collapse at soil level. Damping off (a seedling rot caused by soil fungi) strikes in wet, cold mix, so use fresh seed-raising mix and water less often. Read more

Flowering stops in midsummer. Dry soil and uncut seed heads both end flowering early, so water in long dry spells and deadhead as Deadheading describes.

Stems flop over. Rich soil, extra fertiliser or shade makes lanky, soft growth, so grow it lean and in full sun, as Three mistakes that matter explains.

Pests and diseases

Few pests trouble lemon mint, and before any spray, read its label and use it only as directed.

Powdery mildew (Golovinomyces and related fungi). A white, powdery film spreads over the leaves, often from late summer and in crowded, humid plantings. Remove affected leaves and spray 1 part full-cream milk to 10 parts water. Read more

Aphids (Aphididae). Clusters of small sap-sucking insects gather on soft new tips, which curl and distort. Squash them by hand or knock them off with a strong jet of water. Otherwise, late in the day once bees have left, spray insecticidal soap on leaf undersides, never onto open flowers. Read more

Slugs and snails (Gastropoda). They chew young seedlings to the ground overnight, most often after rain. Search with a torch after dark and remove them. Read more

Prevention first

• Keep plants at the spacing Sowing Seeds gives, so air moves between them.
• Water the soil rather than the leaves, and water in the morning so plants dry before night.
• Keep mulch pulled back from young seedlings, because snails hide in mulch and under pots.
• Grow flowering herbs nearby to keep aphid predators in the garden, as hoverflies explains.

Tips

1. Plant it in a drift rather than as a single plant. Massed flowers suit bees, butterflies and native bees, and make a better show in a border.
2. Pick leaves early in the season for cooking. Later in the season, older leaves often smell more of oregano than lemon.
3. Grow a few extra plants just for drying, because the flowers are excellent in dried arrangements.