How to Grow Linaria in Australia

Linaria (Linaria maroccana), also called annual toadflax or baby snapdragon, is a cool-season annual of the plantain family, Plantaginaceae. It is grown for slender spikes of tiny spurred flowers like miniature snapdragons, in yellow, pink, red, white and purple. It comes from Morocco, suits the mild months in every Australian zone and can flower 8 to 10 weeks from sowing. The usual mistake is burying its dust-fine seed.

Three mistakes that matter

1. Burying the seed. Each seed is under 1 mm long, and seed covered by more than a scant 2 mm of soil often fails to come up. Press it onto the surface or barely cover it, as set out in Sowing Seeds.
2. Sowing into summer heat. Linaria dislikes heat and humidity and usually stops flowering in hot weather, so late spring sowings in warm zones give a short show. Keep to your zone's autumn and winter window under When to plant.
3. Letting the seedbed dry out. Seed lying at the surface dries quickly and heavy rain can wash it away, leaving bare patches. Water with a fine spray or a watering can rose, keeping the surface damp until seedlings show.

When to plant

Seed germinates in cool to mild soil of about 10 to 18°C, and plants grow and flower best through the cool months. Autumn is the main sowing time in every zone, with Anzac Day inside the southern window. Temperate and cool gardens can sow again from late winter into spring.

Near the end of a window, sow only where plants can flower before the summer heat sets in. At the hot edge, a spot with afternoon shade helps plants keep flowering a little longer.

Site, soil and setup

Give linaria full sun, at least 6 hours a day, or light afternoon shade in hot inland and northern gardens. It likes light, free-draining, moderately fertile soil, and sandy ground suits it well. It grows in acid, neutral or alkaline soil, so pH rarely needs correcting.

Damping off fungi carry over between crops in the remains of old plants. If seedlings collapsed in a bed the year before, sow somewhere fresh.

Container growing

Both mixes grow in pots, hanging baskets and window boxes. Choose a pot at least 20 cm wide and 20 cm deep, which holds about 5 L of potting mix, with drainage holes. Fairy Bouquet, at 20 to 30 cm tall, suits pots best. Northern Lights reaches about 60 cm and needs a large tub out of strong wind. Bagged mix can carry Legionella bacteria, so dampen it before opening the bag, wear a mask and gloves, and wash your hands afterwards.

• Watering: once the top of the mix feels dry, water until it drips from the base.
• Feeding: pots run short of food sooner than beds. From the first buds, water on fish and seaweed blend at 25 mL per 9 L every two weeks.
• Position: full sun, or morning sun and afternoon shade in hot zones.

Sowing Seeds

Scatter linaria where it is to flower, or raise it in punnets and plant it out; both methods work.

Sowing direct

• Rake the soil fine and level, then water it before sowing.
• Mix the seed with a little dry sand so it spreads evenly, as described in sowing tiny seeds, and scatter it thinly.
• Press the seed onto the surface, or cover it with no more than 2 mm of fine soil.
• Keep the surface damp with a fine spray; seedlings usually show in 10 to 21 days.
• Thin when seedlings are about 5 cm tall, to the spacing for your mix in the table below.

Starting in trays

• Fill punnets with fresh seed raising mix, sow on the surface and press the seed in lightly.
• Stand them in bright light and never let the mix dry out.
• Harden off the seedlings (give them a little more time outdoors each day over about a week, until they cope with full sun and wind).
• Plant out at 5 to 10 cm tall, once true leaves show. Water each in with half-strength seaweed solution, 15 mL per 9 L.

The two mixes are sown and grown the same way; height sets their spacing and their place in the garden.

Care by growth stage

Linaria is a light feeder that lives mostly on the compost dug in before sowing. Even moisture at the roots, dry leaves and regular picking keep new spikes coming.

If growth stalls in thin, hungry soil, scratch a light dose of all-purpose controlled release granules (NPK around 14-5-10) into the soil beside the plants.

Deadheading

Every spike left to set seed slows the next flush of flowers and scatters seedlings through the bed.

• Every few days: snip faded spikes back to just above a set of leaves.
• Cutting for the vase: counts as deadheading, so pick often.
• After the first big flush: cut plants back to encourage another round of flowers.
• Near bushland or grassland: remove spent spikes before the pods ripen, as the tips below explain.
• End of flowering: pull out spent plants and compost them.

Companion planting

Linaria sits well among other cool-season annuals that share its sun, soil and autumn sowing time.

Grows well with

• Violas: low plants for edging and pots, sown in the same months.
• Calendula: an autumn-sown annual that flowers through the cool months in the same sunny, well-drained spot.
• Vegetable beds: the flowers bring bees and butterflies, part of a pollinator garden.

Keep apart

• Sunflowers on the sunny side: a tall row leaves linaria in shade for much of the day.
• Pumpkins and other sprawling vines: their big leaves smother low, slender plants.

Harvesting Blooms

Cut stems for the vase when the lowest two or three flowers on a spike have opened.

• Pick in the cool of the morning and take the longest stem you can.
• Strip any leaves that would sit under water, and stand the stems in a clean bucket of water as you go.
• Dip the cut ends in boiling water for about 10 seconds to help them last. Keep the flowers clear of the steam, then stand the stems in cool water.

In clean water, cut stems often last about a week, with buds higher on each spike opening as they go. Use the spikes in small jugs, posies and mixed jars, and leave some in the bed for the bees.

Common problems

Bare patches after sowing. Seed buried too deep, a dry surface or seed washed away by heavy rain is the usual cause. Three mistakes that matter covers each. Read more

Seedlings topple overnight. Damping off (a rot of young seedlings, mostly from Pythium species and Rhizoctonia solani) is worst where mix or soil stays wet. Read more

Plants yellow and rot at the base. Root rot fungi in waterlogged soil cause it; remove affected plants and improve drainage as set out in Site, soil and setup.

Flowering stops as summer arrives. Heat is the usual cause, as Three mistakes that matter explains. Cutting plants back, as in Deadheading, can bring a smaller flush if the weather cools.

Pests and diseases

Serious trouble is uncommon: snails go for seedlings, sap-suckers gather on soft growth and mildew finds crowded plants.

Garden snail (Cornu aspersum) and grey field slug (Deroceras reticulatum). They feed after dark, most of all on wet nights, chewing seedlings to the ground and leaving silvery trails. Hunt them with a torch about two hours after sunset, and set beer traps nearby. Read more

Aphids (family Aphididae). These small sap-suckers cluster on new tips and the undersides of leaves and leave sticky honeydew. Knock them off with a strong jet of water, or spray insecticidal soap under the leaves. Read more

Powdery mildew (fungi of the order Erysiphales). White powdery patches spread across the leaves, worst in crowded, sheltered plantings. Pick off the worst leaves and spray early outbreaks with 1 part full-cream milk to 10 parts water. Read more

Prevention first

• Thin to the full spacing in Sowing Seeds, so leaves dry quickly after rain.
• Water the soil, not the leaves, early in the day.
• Use fresh seed raising mix and a scrubbed tray for every sowing.
• Check tips and flower spikes once a week while plants are flowering.

Tips

1. For a meadow of colour, scatter Northern Lights thickly over a bare, sunny patch instead of sowing in rows.
2. Sow a second batch three or four weeks after the first for a longer run of flowers.
3. The short spikes of Fairy Bouquet suit small hands, which makes linaria a good first flower for growing from seed with kids.
4. Linaria self-seeds and is recorded as naturalised in Western Australia. Near bushland, deadhead before pods ripen and check your council's weed advice. It is a different plant from yellow toadflax (Linaria vulgaris), a perennial naturalised in Victoria and New South Wales.