How to Grow Foxgloves in Australia

Foxglove (Digitalis purpurea) is a biennial or short-lived perennial in the plantain family (Plantaginaceae), grown for its tall spires of spotted bells. It lights up moist, part-shaded beds in spring and early summer, but every part of the plant is poisonous. The usual mistake starts on day one: burying the dust-fine seed, which needs light to germinate.

Three mistakes that matter

1. Covering the seed. Foxglove seed needs light to germinate, so seed buried under mix or soil often never comes up. Press it onto the surface of moist mix, leave it uncovered and keep it in bright light out of direct sun.
2. Planting in hot sun and dry soil. Foxgloves are woodland plants, and drought stress cuts flowering. Give them morning sun and afternoon shade, soil rich in organic matter, and a deep drink whenever the top few centimetres dry.
3. Sowing once and expecting flowers every year. The tall mixes flower in their second season, set seed and usually die. Sow a fresh batch every autumn, or leave a few spikes to self-seed where that is safe, so there are flowering plants each spring.

When to plant

Sow from late summer through autumn, once the worst heat has passed, so seedlings grow on in cool weather. Seed germinates best at 18 to 21°C. Each plant spends its first months as a flat, leafy rosette, lives through winter, and sends up its flower spike from spring.

In hot inland and western districts, wait for the first cool change of autumn, which Anzac Day often marks. Sown under cover in late winter, 'Foxy' can flower the same summer, about five months later.

Site, soil and setup

A spot that stays cool and moist at the root, with shelter from hot, drying wind, suits foxglove best. Choose it with the grown height in mind.

The three mixes in the foxglove seed range differ mainly in height and in how soon they flower, which decides where each one goes.

Container growing

'Foxy' is the natural choice for a pot, which also keeps seed out of the garden. Give one plant a pot at least 30 cm across, about 15 L, of good-quality potting mix. Tall mixes need 40 cm across, about 30 L, and a stake.

• Watering: keep the mix slightly moist but never waterlogged, checking daily in summer; see watering pots in summer.
• Feeding: fish and seaweed blend at 25 mL per 9 L every fortnight, from the first sign of a spike until flowering ends.
• Position: a sheltered spot in light shade, out of hot afternoon sun and wind.
• Winter: stand the pot on feet so it drains freely while the rosette waits for spring.

Sowing Seeds

Raise foxgloves in a tray under cover, where the tiny seed is easy to watch, or scatter it straight onto a prepared bed.

Preparation

The seed needs no soaking, chilling or scratching before sowing. It is as fine as dust, so mix a pinch with dry sand and sprinkle the mixture, as in sowing tiny seeds. Wear gloves to handle seed and seedlings, and wash your hands afterwards.

Starting under cover

• Fill a tray or cells with fresh seed raising mix and water it well before sowing.
• Scatter the seed thinly over the surface and press it in gently. Do not cover it.
• Lay clear plastic with a few holes over the tray to hold moisture, and stand it in bright light out of direct sun.
• Mist the surface whenever it starts to dry. Seedlings usually appear in 14 to 21 days, though some seed lots take several weeks longer.
• Prick out (lift each seedling by a leaf into its own cell) once the first true leaves show.

Sowing direct

Rake the soil to a fine tilth and water it. Scatter the seed and sand thinly and press it in with the back of the rake. Keep the surface moist with a fine spray until seedlings show. Thin them in stages to 30 to 45 cm apart.

Transplanting

Plant out when seedlings are 5 to 10 cm tall with true leaves. Harden them off first (a week or so of gradually longer spells outdoors that toughens soft growth), as in hardening off seedlings. Set each plant 30 to 45 cm apart with the crown level with the soil. Water in with seaweed solution at 30 mL per 9 L.

Care by growth stage

Even moisture decides how big the rosette grows, and a big rosette decides the spike. Plants usually flower once the rosette is more than 15 to 20 cm across.

Weeks count from an autumn sowing. Rosettes that are still small in spring repeat the rosette rows for another year before flowering. Mulch with a 5 cm layer of compost, clear of the crown. If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched in as the spike appears can help.

Sheltered plants rarely need support, but the tall mixes can snap in exposed spots. Push in a stake at planting, so no roots are speared later. Tie the spike loosely with soft twine as it grows.

Deadheading

Deadheading decides whether foxglove flowers again, lives on or spreads.

• Cut each spent spike off at its base as soon as the flowers finish.
• Side spikes often follow, smaller than the first.
• Cutting before seed sets can help a plant live and flower for another year.
• Leave one or two spikes to ripen only where self-sown seedlings are welcome and no bushland is nearby.
• Put spent spikes in the general waste bin, not the compost, so seed does not travel.

A single plant can produce 1 to 2 million seeds. Garden escapes have invaded wet forest in Victoria, including Kinglake National Park. In Tasmania foxglove is a declared weed and sowing it is prohibited, so check your state or council weed list elsewhere.

Companion planting

Foxglove belongs at the middle or back of a shaded cottage border, well away from anything that goes into the kitchen.

Grows well with

• Delphinium, another tall, cool-season spire that likes the same rich, moist soil.
• Violas along the front edge, which flower in the cool months and hide the base of the spikes.
• Cornflowers, an autumn-sown cottage annual that flowers alongside it in spring.

Keep apart

• Vegetable and herb beds, especially comfrey and borage, whose leaves the foxglove rosette has been mistaken for.
• Chook runs and paddocks, because every part is poisonous to animals.
• Bushland edges and creek lines, where escaped seed becomes a weed.

Harvesting Blooms

Cut a spike for the vase when the lowest third of its flowers are open and the rest are still in bud.

• Pick early in the morning, when stems are full of water.
• Use sharp, clean secateurs.
• Carry a bucket of water and stand each spike in it straight after cutting.
• Strip any leaves that would sit below the waterline.
• Arrange the spikes upright, because a spike laid at an angle curves its tip upwards.

Spikes often last a week or more in a vase. Change the water whenever it turns cloudy. Stems waiting to be arranged keep best somewhere cool, about 4 to 15°C.

Stand tall spikes alone in a heavy jug, out of reach of children and pets.

Common problems

Seeds did not come up. Buried seed, a dry surface or a hot spell during germination are the usual causes; see Three mistakes that matter. Read more

No flower spike in the first year. The tall mixes spend their first season as a rosette and flower in the second, once it has passed through winter.

Rosettes stayed small. Crowded or dry plants often wait an extra year to flower. Thin or move them while they are small.

The plant died after flowering. That is the normal end of a biennial, as plant life cycles explains; see Three mistakes that matter.

Seedlings everywhere. Spikes left to ripen shed seed freely; see Deadheading.

Pests and diseases

Foxglove has few serious troubles, and most strike seedlings or plants in the wrong spot.

Slugs and snails (Gastropoda). They chew young seedlings, and plants become less tasty as their leaves grow hairier. Check under leaves and around rocks where they shelter by day, and set shallow beer traps dug slightly into the soil. Read more

Aphids (Aphididae). These soft green, black or brown insects, about 2.5 mm long, can colonise the developing flower spike. Hose them off gently without snapping the stem, and for repeat outbreaks spray soapy water or horticultural oil, never in hot weather. Read more

Powdery mildew (Oidium and related fungi). Fine white patches spread across the leaves, usually late in the season, and plants often recover without treatment. Water at the base in the morning, remove the worst leaves, and try a spray of 1 part full-cream milk to 10 parts water. Read more

Crown rot (soil-borne fungi and water moulds). Dense crowns can rot in soggy, poorly drained soil, and the rosette collapses. Lift and bin the plant with its roots, then fix the drainage before replanting; see waterlogged soil.

Prevention first

• Plant in free-draining, humus-rich soil and water at the base, not over the leaves.
• Keep seedlings in pots or behind a barrier until their leaves turn hairy and tough.
• Keep the full spacing between plants so air moves around the rosettes.
• Clear spent spikes and dead leaves promptly, as in garden hygiene.

Tips

1. Self-sown seedlings move easily while small: lift each with all its roots and replant it where you want it.
2. Label trays and rosettes as poisonous, so nobody mistakes the soft leaves for a weed to pull barehanded or a herb to pick.
3. Bees work the flowers for nectar, so keep sprays off open spikes.