How to Grow Impatiens in Australia

Impatiens covers two frost-tender plants of the balsam family, Balsaminaceae, both grown as annuals: busy Lizzie (Impatiens walleriana) and garden balsam (Impatiens balsamina). Busy Lizzie is grown for flat flowers that keep coming in shade, and balsam for cup-shaped blooms in sun or part shade. Their ripe seed pods burst at a touch, which gives the genus its name. Most failures happen in the seed tray, because busy Lizzie seed needs light and real warmth to come up.

Three mistakes that matter

1. Burying busy Lizzie seed. The seed needs light to germinate, so seed covered with mix, or kept much below 22°C, often never comes up. Press it onto the surface of a warm tray, as set out in Sowing Seeds.
2. Hot afternoon sun on busy Lizzie. Too much sun scorches the leaves, and plants wilt quickly in hot, dry spells. Give busy Lizzie bright shade or morning sun, and keep the sunnier spots for balsam (see Site, soil and setup).
3. Planting out too early. Both species are frost tender, and soft seedlings set out into cold nights stall or die. Harden them off and plant out once the last frost has passed, around Melbourne Cup weekend in Melbourne and cooler districts.

When to plant

Warmth decides it: both species germinate at 22 to 24°C. Southern gardeners start trays indoors or on a seedling heat mat weeks before the weather warms. Busy Lizzie is slow, with about 9 to 12 weeks in trays and pots before planting out, and balsam is quicker.

Where a window opens before the last frost, keep seedlings under cover until it passes. Late sowings in the south flower for only a few weeks before cold nights stop them.

Site, soil and setup

Busy Lizzie does best in part to full shade, and copes with some sun only where the soil stays moist. Balsam wants full sun or part shade, with at least 3 hours of direct sun a day. Both need moist, free-draining soil rich in organic matter, slightly acidic to neutral.

Busy Lizzie has jumped garden fences in south-eastern Queensland and coastal New South Wales, and grows wild along creeks and forest edges there. Brisbane City Council lists it as pest vegetation, so check with your council before planting it. Do not replant impatiens where downy mildew struck (see Pests and diseases).

Container growing

Both varieties stay compact, about 25 to 30 cm tall, and suit pots, window boxes and hanging baskets. Choose a pot of at least 10 L with drainage holes, such as one 30 cm across, which holds about 13.5 L. Legionella bacteria live in bagged potting mix, so wear a mask and gloves when handling it and wash your hands afterwards.

• Watering: check pots daily in warm weather and soak them once the top few centimetres feel dry.
• Feeding: from the first flowers, water on fish and seaweed blend at 25 mL per 9 L each fortnight.
• Position: bright shade or morning sun for busy Lizzie; a sunnier spot for balsam, out of strong wind.

Sowing Seeds

Start both species in trays or punnets under cover, then transplant them, because the seed needs steady warmth that garden soil seldom gives.

Starting under cover

• Fill a clean tray with fine seed raising mix and water it well before sowing.
• Busy Lizzie: press the tiny seed onto the surface and leave it uncovered, as fine seed needs light.
• Balsam: cover the larger seed with fine mix, no deeper than 6 mm.
• Keep the mix at 22 to 24°C and damp, never wet; seedlings usually show in 7 to 10 days, balsam sometimes in 14 to 21.
• Move the tray off any heat mat once most seedlings are up, into strong light.

Growing on and planting out

• Pot each seedling into its own cell once its first true leaves open.
• Grow them on at 18 to 22°C by day and 16 to 18°C at night.
• Harden off the young plants (a week or two of lengthening daily spells outdoors, until they cope with sun and wind).
• Plant out at 5 to 10 cm tall, busy Lizzie 25 to 30 cm apart and balsam 30 to 35 cm apart.
• Settle each one in with half-strength seaweed solution, 15 mL per 9 L.

The two varieties differ in light and in how their seed is sown.

Care by growth stage

Impatiens are light feeders, and steady moisture decides how well they flower. Mulch the bed with 5 cm of compost after planting to keep the roots cool and damp.

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

Deadheading

Removing faded flowers and young pods stops seed forming, which keeps plants flowering and stops self-sown seedlings spreading.

• Balsam: every few days, snip each faded flower and swelling pod just above a leaf.
• Busy Lizzie: pick off spent flowers and any young pods as you water.
• Leggy busy Lizzie in late summer: cut the whole plant back by a third to bring on fresh flowers.
• Seed for next year: leave a few pods on the best balsam plants, as Harvesting Blooms describes.

Companion planting

Good partners share the steady moisture impatiens need.

Grows well with

• Violas: they like the same evenly moist soil and afternoon shade, and fill the bed through the cool months after impatiens finish.
• Marigolds: compact types manage part shade, so they suit a sunny edge beside balsam.
• Petunias: they take the full-sun end of a bed or basket, with balsam in the part shade.

Keep apart

• Lavender: the steady water impatiens need keeps its soil too wet.
• Thyme: it wants lean soil and dry roots, the opposite of an impatiens bed.

Harvesting Blooms

Balsam often flowers 8 to 12 weeks from sowing and busy Lizzie at about 12 weeks, and both keep flowering until frost. The main harvest after the flowers is balsam seed.

• Leave a few pods on the strongest balsam plants.
• Pick pods as they turn from green to yellow.
• Slip a paper bag over each pod before touching it, because ripe pods burst.
• Collect on a dry day and tip the seed onto a paper towel.
• Before autumn frost, take 10 to 15 cm busy Lizzie tip cuttings and root them in water.

Dry the seed on the paper towel overnight, then store it in a paper bag inside a labelled glass jar in a cool, dark place. Sow saved balsam seed the following spring, and keep rooted busy Lizzie cuttings as pot plants in a bright, frost-free spot through winter. Balsam is not a food plant, because its leaves hold calcium oxalate.

Common problems

Bare trays after sowing. Buried busy Lizzie seed or cold mix is the usual cause; the first of the Three mistakes that matter covers the fix. Read more

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

Long, pale, floppy seedlings. They are stretching for light, often because the tray stayed on the heat after the seedlings came up. Read more

Plants wilt every afternoon. Busy Lizzie in too much sun or drying soil flags in the heat; the second of the Three mistakes that matter covers the fix.

Stems soften and collapse at the base. Waterlogged soil rots the fleshy stems, so let the surface dry a little between waterings.

Pests and diseases

Downy mildew is the serious threat to busy Lizzie; the rest trouble most soft, leafy plants.

Impatiens downy mildew (Plasmopara obducens). Leaves turn pale, mottled and yellow, with white growth underneath, then drop until plants collapse. Pull and bin affected plants rather than composting them, and plant other flowers in that bed for at least a year. Read more

Two-spotted mite (Tetranychus urticae). Leaves show fine yellow stippling, and numbers climb fast in hot, dry weather. Hose the leaf undersides with a firm jet three mornings running, and keep plants well watered. Read more

Aphids (family Aphididae). These small sap-suckers gather on new shoots and under leaves, leaving sticky honeydew. Hose them off, or spray insecticidal soap. Read more

Garden snail (Cornu aspersum) and slugs. They chew seedlings and soft leaves at night, leaving silvery trails. Collect them by torchlight about two hours after sunset, and clear boards and debris where they shelter. Read more

Prevention first

• Sow in fresh seed raising mix in a scrubbed tray.
• Water at the base in the morning so leaves dry quickly.
• Keep the full spacing from Sowing Seeds for airflow.
• Check leaf undersides weekly once plants are flowering.

Tips

1. Never tip old busy Lizzie plants or prunings into bushland or over the back fence: stem pieces take root and seed travels in water.
2. Balsam is also called touch-me-not, and children love popping the ripe pods; it makes a good first flower for growing from seed with kids.
3. Mix a few begonias into shady beds of busy Lizzie, because downy mildew attacks only impatiens and the begonias keep flowering if it strikes.