How to Grow Aquilegia in Australia

Aquilegia (Aquilegia vulgaris and its hybrids), also called columbine or granny's bonnet, is a short-lived perennial in the buttercup family (Ranunculaceae). It is grown for its nodding, spurred flowers on wiry stems in spring, held above fern-like, blue-green leaves. It suits a part-shaded cottage bed, a pot and the vase, and the usual mistake is sowing the seed warm, straight from the packet.

Three mistakes that matter

1. Skipping the chill. Aquilegia seed holds a dormancy that a spell of moist cold breaks. Unchilled seed comes up slowly and patchily, or not at all. Give it 3 to 4 weeks in the fridge first, as under Sowing Seeds.
2. Burying the seed. Light helps the seed germinate, so a deep covering of mix can stop it coming up. Press it onto the surface of moist mix and cover it with no more than 3 mm of fine mix or vermiculite.
3. A hot, dry or soggy spot. Afternoon sun in warm districts scorches the leaves and cuts short an already short life, while wet, heavy soil rots the crown. Plant in part shade, in moist soil rich in organic matter that drains freely.

When to plant

Chilled seed germinates best in mild conditions, around 15 to 24°C. That makes aquilegia mainly an autumn sowing, started as the heat breaks, often around Anzac Day. Autumn sowings build a leafy clump through winter and usually flower the following spring. Cool gardens have a second window in early spring. Plants usually live two to four years.

Spring sowings that meet hot weather as small seedlings need shade and steady water, and many wait until their second spring to flower. In cool gardens such as Canberra and the tablelands, pots of seed sown in autumn and left outdoors get their chill from the winter itself.

Site, soil and setup

Columbines grow wild along woodland edges, and they do best in a spot that copies one: dappled light and a cool, moist root run. Choose it as a lasting home, because self-sown seedlings tend to appear around the parents for years.

A bed on the shady side of a house or fence, or under deciduous trees, gives winter light and summer shade. For more on testing and adjusting your ground, see soil pH.

Container growing

Aquilegia grows well in a pot, which can follow the shade through the year. Use a pot of at least 10 L, about 25 cm across and as deep, filled with a quality potting mix. The mixes differ mostly in height.

• Watering: keep the mix evenly moist but never soggy, and check it daily in hot weather; see watering pots in summer.
• Feeding: fish and seaweed blend at 25 mL per 9 L every fortnight, from late winter until the buds show colour.
• Position: morning sun and afternoon shade, moved into full shade during heatwaves.
• Renewal: replace potted plants with fresh seedlings every two or three years, as they tire.

Sowing Seeds

Chill the seed and raise it in pots under cover, or sow outdoors in autumn where winter does the chilling.

Preparing the seed

Cold stratification (a spell of moist cold that breaks the seed's dormancy) makes germination far more even. Fold the seed into a damp, not dripping, paper towel, or mix it with a spoonful of damp vermiculite. Seal it in a labelled bag in the fridge, at about 4°C, for 3 to 4 weeks. Sow it within a week of taking it out. The seed treatments article explains the method.

Starting under cover

• Fill small pots or cells with fresh seed raising mix and water it well before sowing.
• Scatter the chilled seed thinly, press it onto the surface and cover it with no more than 3 mm of fine mix or vermiculite.
• Keep the pots in bright light out of direct sun, at the temperature under When to plant, and mist to keep the surface moist.
• Seedlings usually appear in 3 to 4 weeks, and some seed takes longer.
• Prick out each seedling into its own 7 to 9 cm pot once it has its first true leaves, holding it by a leaf.

Sowing direct

In cool and alpine gardens, and inland where winter nights bring frost, seed can go straight into a finely raked bed in autumn. Winter cold does the chilling, and seedlings come up as the soil warms. Mark the spot and keep weeds and snails away from the seedlings.

Transplanting

Seedlings are usually ready to plant out 4 to 6 weeks after they come up, once roots fill the pot. Harden them off first (a week or so of gradually longer spells outdoors that toughens soft growth), as in hardening off seedlings. Set each crown level with the soil surface, 30 to 50 cm apart, with McKana Giants at the wider spacing. Water in with seaweed solution at 30 mL per 9 L and mulch around the plant, keeping mulch off the crown.

Care by growth stage

Even moisture and a cool root run decide how well aquilegia flowers and how long it lasts. Established plants need little feeding, so go lightly.

Weeks count from sowing chilled seed in autumn. From the second year, the clump repeats the last four rows each season. If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched in each late winter can help.

Deadheading

Removing spent flowers keeps a clump tidy, can lengthen flowering and limits self-sown seedlings.

• Cut each flower stem down to the leafy clump as its flowers fade.
• Once flowering ends, cut the whole plant back to the base and water it well; fresh leaves usually follow.
• To collect seed or let plants self-sow, leave a few stems until the pods turn brown.
• Near bushland, remove every spent stem before seed ripens. Columbine has escaped from gardens into moist forest in Victoria's Dandenong Ranges and alpine resorts.
• Trim off leaves that turn yellow or brown in autumn, leaving the newer rosette in the centre.
• Bin, rather than compost, any leaves carrying powdery mildew.

Companion planting

Aquilegia belongs in the front or middle of a part-shaded border, among plants that take over once its flowers finish.

Grows well with

• Delphinium, whose taller spires stand behind the clump in cool cottage borders.
• Violas along the front edge, which share the cool, moist, part-shaded conditions.
• Love-in-a-mist and hardy geraniums, which suit the same relaxed cottage planting.

Keep apart

• Mint and other spreading runners, which crowd the crown and compete for moisture.
• Dense, tall plantings that block air flow, which encourages powdery mildew.
• Annual beds dug over every season, where self-sown seedlings and the crown are easily speared.

Harvesting Blooms

Cut a stem for the vase when about half of its flowers are open.

• Pick early in the morning.
• Carry a bucket of water and stand each stem in it straight after cutting.
• Cut long stems right down to the leafy rosette, which can encourage more stems.
• Strip any leaves that would sit below the waterline.
• Re-cut the stems indoors and stand them in clean, cool water.

Cut columbines usually last 5 to 7 days in a vase. Stems that will not be displayed straight away keep for a day or two somewhere cool, between about 4 and 15°C.

Mix them loosely with other cottage flowers, where the nodding bonnets and blue-green leaves soften firmer blooms.

Common problems

Seeds did not come up. Unchilled seed, a deep covering or mix that dried out are the usual causes; see Three mistakes that matter. Read more

No flowers in the first spring. Spring sowings and small plants often wait a year; see When to plant.

Plants disappeared after a few years. Aquilegia is naturally short-lived; let a few pods self-sow or sow fresh seed every year or two.

Seedlings look different from the parents. Aquilegias cross freely with others nearby, so self-sown and saved seed rarely comes true. Sow fresh seed of a mix to keep its colours.

Pests and diseases

Aquilegia has few serious troubles, and most start with soft growth, crowding or wet soil.

Aphids (Aphididae). These soft green, black or brown insects, about 2.5 mm long, cluster on new growth and buds and distort the leaves. Hose them off or prune the worst tips, and for repeat outbreaks spray soapy water or horticultural oil, never in hot weather. Read more

Slugs and snails (Gastropoda). They chew seedlings and new spring growth. Check around rocks and pots where they shelter by day, and set shallow beer traps dug slightly into the soil. Read more

Thrips (Thysanoptera). These tiny insects, usually 1 to 2 mm long, leave silvery-brown speckling and streaks on leaves. Hang yellow sticky traps and spray insecticidal soap every week for four to six weeks. Read more

Powdery mildew (Erysiphe aquilegiae). White powdery patches spread across the leaves, most often on crowded plants. Thin congested growth, remove affected leaves and spray 1 part full-cream milk to 10 parts water. Read more

Crown rot (soil-borne fungi and water moulds). It strikes in heavy soil that stays wet, and the whole plant wilts and collapses. Lift and bin a dead plant with its roots, then fix drainage before replanting.

Prevention first

• Plant in free-draining soil and water at the base in the morning, not over the leaves.
• Space plants 30 to 50 cm apart so air moves freely between them.
• Check new growth at dusk in spring for snails, and the buds for aphids.
• Keep broad sprays off the bed so ladybirds, lacewings and hoverflies can keep aphids and thrips down.

Tips

1. To save seed, cut the stems once the pods dry and turn brown, and let the seed fall into a paper bag. Store it cool and dry, and chill it before sowing.
2. The nectar-rich flowers draw bees, butterflies and small birds, which makes a clump useful beside the vegie patch; see gardening for bees.
3. Self-sown seedlings move well while small but are delicate, so lift each one with a ball of soil.