Name: foxglove, Digitalis purpurea, Digitalis grandiflora, Digiplexus “Illumination Flame” and “Ruby Glow”
Plant type: biennial or true perennial. Grows the first year and dies in the second (biennial). Some species are perennial, though usually short-lived.
Height: usually 0.5–2m tall; some may require stakes
Foliage: forms a rosette of foliage with oval, oblong or lance-shaped leaves.
Climate: grows naturally in woodland area conditions and tolerates very low temperatures, thus requiring a cool, or warm temperate climate.
Soil: a well-drained, humus-rich soil is preferred.
Position: can grow in many different positions, including full sun, but the best growing environments consist of partial shade with protection from hot drying winds under trees.
Flowering and fruiting: colourful spikes of single, two-lipped, trumpet-shaped flowers arise from the foliage rosettes in spring.
Feeding: use a controlled-release organic fertiliser specifically for flowering plants in early spring. Liquid feed after flowering and again in late summer/early autumn if required.
Watering: regular watering 2–3 times per week is required throughout the hotter summer months.
Foxglove is derived from the genus Digitalis, which encompasses varieties considered to be evergreen perennials or biennials, depending on the species. Growing from seed, the foliage will form from a tight rosette with no stem, generally growing the first year and then blooming the following spring with a mass of colourful, bell-shaped spikes of two-lipped tubular flowers.
Colours range from pink, purple, magenta, white, lavender and orange, often with spotted throats, to a plethora of bi-colour varieties. Foxglove’s final height can vary from as little as 50cm to around 1.8m, with taller varieties sometimes requiring staking to increase vertical stability.
Foxglove originates from the European region, including Great Britain, Spain and Norway, alongside areas of Central Asia and northwest Africa. Due to its widespread origins, foxglove has proved to be an adaptable plant, capable of flourishing in multiple climates. Temperatures as low as –25°C with harsh frosts are tolerable. In Australia’s warm temperate climate, foxglove generally requires partial shade and protection from hot drying winds to ensure the soil does not become overly dry.
New hybrid perennial varieties such as Digiplexis were developed in England, crossing Digitalis (the common foxglove plant) with the Mediterranean Isoplexis genus or Canary Island foxglove. Unlike the Digitalis variety, which produces a single spike of flowers, Digiplexus “Illumination Flame” has several further simultaneous blooms, and flowers from spring through to autumn, thriving in cool temperate conditions with high light intensities (not heat).
All foxglove varieties can be successfully grown in pots, but due to their height and need for spacing, larger pots are required. They suit both formal and cottage-style planting, and are at their best in mixed borders with roses and other perennials, or planted in groups en masse.
The best time to plant foxglove in Australia is from spring to early summer.
Foxglove requires a slightly acidic environment within humus-rich soil. There should be a balance between good drainage and water retention so that the soil is not overly wet. The best growing conditions consist of a pH around 6.5–7, which can be easily monitored with a soil pH kit. Apply compost around the plant during spring, and ensure that it is kept well-watered throughout summer.
In pots and containers always use a premium potting mix, and keep well-watered throughout summer.
Depending on the quality of the soil, little to no fertiliser is required. However, controlled-release organic fertiliser pellets are ideal to scatter around the growing plant at the beginning of spring. Ensure the fertiliser is not directly in contact with the foliage, to avoid chemical burns to the leaves.
Major problems encountered with foxglove are related to the soil conditions and watering. Over-watering and a build-up of moisture can cause crown rot and mildew, killing the plant at its roots before it has the chance to flower. To avoid this, ensure adequate spacing between plants to allow proper air circulation. Other issues include the risk of Anthracnose, a fungal disease causing brown spots on the leaves, which transform to black, targeting weaker plants. Prevention includes sufficient fertilising to allow the plant to grow healthy and strong, so it’s not vulnerable to the disease, or treatment through the use of a copper-based fungicide. Aphids can weaken the health of a foxglove—their presence can be identified from yellow wilted patches. This issue can be easily controlled with the introduction of predators such as ladybugs, or the use of insecticides.
Perennial types can either be divided or propagated through basal cuttings. when using this cutting technique, select a plant 10–12cm tall, so that the base is strong and will root, rather than hollow out and rot. Biennial and perennial species will seed naturally, and the seed can be collected and sown during late summer/early autumn or early spring. The gathered seeds need light to germinate, so it is important to sow them on the surface of well-composted soil in the garden, or on the surface of a seed-raising mix under glass. Spacing is important to avoid overcrowding and fungal diseases.
Delphinium: statuesque perennial for the back of the herbaceous border, flowering in summer in tones of blue, white, pink and purple.
Penstemon: small perennial with showy flower spikes in blues, reds, pinks, white and bi-colours from spring through to summer.
Poppies (Papaver): annuals, biennials and perennials with cupped petals and vibrant red, white, purple or pink blooms in spring.
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