Foxglove penstemon

Sun

Full sun; tolerates light afternoon shade, especially in hot climates.

Water

Water regularly while establishing; afterward, water during prolonged drought rather than keeping the soil consistently moist.

Soil

Well-drained sandy, gravelly or rocky soil of low to moderate fertility; tolerates limestone soils but dislikes waterlogged ground.

Height

1-3 ft (0.3-0.9 m)

Spread

1-2 ft (0.3-0.6 m)

Flowers

Late spring to early summer; large white, pale pink, lavender or violet flowers, often with darker purple markings inside.

Foliage

Green, opposite, lance-shaped leaves with toothed edges; basal leaves may persist through mild winters.

Growth

Moderate

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.3 ft (0.4 m)

3. After 2 years

   1.6 ft (0.5 m)

4. After 3 years

   2 ft (0.6 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the US

Growth rate

Moderate

• Plant with the crown at soil level in a sunny position with excellent drainage.
• Water deeply during establishment, allowing the surface soil to dry between waterings.
• Avoid rich manure and routine high-nitrogen feeding, which encourage weak, leafy growth.
• Keep damp organic mulch away from the crown; use a thin gravel mulch if needed.
• Leave a few seed stalks to ripen so seedlings can replace aging plants.

Pruning. After flowering, cut spent flower stalks back to the basal foliage unless you want seed. Remove dead stems and damaged leaves in early spring without cutting into the crown.

Late winter

If sowing indoors, give seed a cold, moist treatment before moving it into warmth; germination can be uneven.

Early spring

Remove dead stems and check that winter moisture has not left the crown sitting in wet soil.

Spring

Plant young plants after the soil becomes workable, spacing them about 1-2 ft (0.3-0.6 m) apart.

Late spring

Water new plants during dry spells and watch for slugs around emerging growth.

Early summer

Remove faded flower stalks, or retain a few for seed.

Autumn

Collect dry seed capsules or sow seed outdoors so it receives natural winter chilling.

• Plant in small groups near the front or middle of a sunny perennial border, where the large flowers can be seen closely.
• Combine with prairie grasses and other central US wildflowers for a loose, naturalistic planting.
• Use in a gravel garden or raised bed where sharp drainage protects the crown.
• Place beside paths in a pollinator garden to watch bumblebees entering the flowers.

Garden styles it suits: Native meadow, Midwest prairie, Texas Hill Country, Pollinator garden, Dry gravel garden and Cottage garden.

Plant it with: Little bluestem, Prairie dropseed, Butterfly weed, Lanceleaf coreopsis, Purple prairie clover and Winecup.

Wildlife: The large tubular flowers provide nectar and pollen for bumblebees and other bees. Bumblebees are particularly well suited to entering and pollinating the flowers.

• Crown and root rot in wet soil: improve drainage or move plants to a raised or gravelly bed; avoid frequent watering.
• Slugs and snails damaging young growth: inspect at dusk, remove hiding places and use suitable slug controls if necessary.
• Powdery mildew in crowded, poorly ventilated planting: increase spacing and avoid excessive nitrogen feeding.
• Plants disappearing after a few seasons: this species can be short-lived, so retain seedlings or raise replacements from seed.

Not known to be toxic to people, cats, dogs or horses, although species-specific toxicity information is limited. No part is recognized as a serious poisoning hazard, but it is not an edible plant. Despite its common name, it is not a true foxglove (Digitalis), which is highly poisonous.

• Common foxglove (Digitalis purpurea)

  True foxglove has alternate leaves and usually taller spikes with flowers hanging mainly along one side. Foxglove penstemon has opposite stem leaves and a conspicuous sterile fifth stamen inside the flower.

• Foxglove beardtongue (Penstemon digitalis)

  This similarly named species has smaller, narrower, usually white flowers in more branched clusters; P. cobaea has much larger, broad-mouthed flowers.

• Large-flowered beardtongue (Penstemon grandiflorus)

  It has smooth, waxy blue-green leaves with largely untoothed edges and upper leaves that clasp the stem. P. cobaea has greener, toothed leaves and usually noticeably hairy stems.

Foxglove penstemon refers to the resemblance of its large tubular flowers to those of true foxgloves, while beardtongue describes the hairy sterile stamen inside the flower.

Propagation. Grow from seed sown outdoors in autumn, or cold-moist stratify seed for about 4-8 weeks before spring sowing. Germination requirements vary between seed lots, and plants may not flower until their second year. Take softwood cuttings from healthy, nonflowering shoots in late spring or early summer.

Accepted botanical name

Penstemon cobaea

In the US and Canada

Native in the lower 48 states.

Native range

Arkansas, Iowa, Kansas, Missouri, Nebraska, Oklahoma and Texas.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.