Yellow foxglove (Digitalis grandiflora)

Synonyms: Digitalis ambigua, Digitalis orientalis

Description:

Yellow foxglove (Digitalis grandiflora) is a tall, showy perennial garden flower native to Europe and southwestern Siberia, grown for its spires of pale yellow, tubular blooms [1][2]. It escapes cultivation into meadows, fields, and other disturbed ground, where it has become naturalized in parts of North America [1]. MISIN tracks it because, like all foxgloves, every part of the plant contains natural chemicals (cardiac glycosides) that are toxic if eaten [3].

Habit:

Yellow foxglove is an upright perennial, typically 2.5 to 4 feet tall, with lance-shaped to oval leaves that are hairy on the underside [1]. It is easiest to identify in May and June, when it sends up a tall flowering spike lined with pale yellow, tubular, bell-like flowers, each about 1.5 to 2 inches long [1]. Cutting the main flower stalk back to the base of the plant before it sets seed can sometimes coax a second, smaller bloom later in the season [1].

At-a-glance cues:

1. Upright perennial, 2.5 to 4 feet tall, with a tall flowering spike [1]
2. Lance-shaped to oval leaves, hairy on the underside [1]
3. Pale yellow, tubular, bell-shaped flowers about 1.5 to 2 inches long, blooming May?June [1]
4. Stem is noticeably hairy, unlike the smooth (hairless) stem of the related Grecian foxglove [1]

Leaves:

1. Arrangement: simple, alternate [1]
2. Shape: lance-shaped to egg-shaped [1]
3. Margin: smooth, untoothed [1]
4. Surface: hairy or fuzzy on the underside [1]
5. Size: about 2.75 to 10 inches (70 to 250 mm) long and 0.8 to 2.4 inches (20 to 60 mm) wide [1]

Stems:

1. Habit: an upright, self-supporting herbaceous perennial (sometimes behaving as a biennial), 2.5 to 4 feet (70 to 120 cm) tall [1]
2. Surface: hairy, unlike the smooth stem of the closely related Grecian foxglove [1]

Flowers:

1. Color: pale yellow [1]
2. Shape: bell- to tube-shaped, five petals fused into a tube, with bilateral (not radial) symmetry [1]
3. Size: corolla about 1.6 to 2 inches (40 to 50 mm) long ? notably longer than Grecian foxglove's roughly 0.8 to 1.2 inches (20 to 30 mm) [1]
4. Arrangement: many flowers along a single tall spike [1]
5. Bloom time: May and June [1]
6. Four stamens per flower [1]

Fruit and seeds:

1. Fruit type: a dry capsule that splits open along seams or pores to release seed when ripe [1]
2. Seeds: many small seeds per capsule, released as the dried capsule splits [1]
3. Ripening: after the May?June bloom
4. Dispersal: tiny, lightweight seeds scatter with wind and can travel in soil, on shoes, and in dumped garden waste

Habitat:

Yellow foxglove is native to Europe and southwestern Siberia and was brought to North America as a garden ornamental, where it has since naturalized in parts of the region, including New England [1][2]. It grows in disturbed ground, meadows, and fields, often persisting near old plantings [1].

Reproduction:

Yellow foxglove spreads mostly by seed [1]. It most often arrives on a property as a garden planting, and its tiny, wind-blown seeds can scatter into nearby meadows and disturbed ground, or travel in soil, on shoes, and in dumped garden waste. As a longer-lived perennial (sometimes behaving as a biennial), an established plant can flower and reseed for several years.

It flowers in May and June and sets seed soon after [1]. Cutting the main flower spike back to the base before seeds form can sometimes trigger a smaller second bloom later in the season ? a trait gardeners use, but one that also means a single plant can produce two rounds of seed in a year if left unmanaged [1].

Impact and Damage:

Every part of a foxglove plant ? leaves, flowers, seeds, and roots ? contains natural chemicals called cardiac glycosides, which are toxic if eaten and can seriously disrupt heart rhythm [3]. This is a genus-wide trait shared with foxglove relatives that MISIN also tracks: in one documented case, a person mistook purple foxglove leaves for the leafy herb borage and cooked them into a pie, leading to dangerously high glycoside levels in her blood and abnormal heart rhythms that required hospital care [3]. Yellow foxglove itself has not been the subject of a similar published poisoning report, but it shares the same class of toxic compounds as its better-studied relatives, so the same caution applies [1][3]. Pets and grazing animals can also be poisoned if they eat the plant.

In gardens, this mainly means keeping curious children and pets away from the plant and never mistaking its leaves for an edible green. In natural areas, yellow foxglove's main concern is that it can establish in meadows and disturbed ground outside where it was planted, adding a toxic plant to habitat used by grazing wildlife.

Similar species:

Yellow foxglove's closest look-alikes are two sibling foxgloves MISIN also tracks.

Grecian foxglove (Digitalis lanata) looks very similar, but its flowers are noticeably smaller ? about 0.8 to 1.2 inches (20 to 30 mm) long, versus yellow foxglove's 1.6 to 2 inches (40 to 50 mm) ? and its stem and leaf undersides are smooth (hairless), unlike yellow foxglove's hairy stem and leaf undersides.

Purple foxglove (Digitalis purpurea) is the most widely recognized foxglove, but its flowers are purple, pink, or white rather than pale yellow, making bloom color the easiest way to tell the two apart.

Monitoring and rapid response:

Signs to watch for:

1. A tall flowering spike, 2.5 to 4 feet, lined with pale yellow, tubular, bell-shaped flowers in May and June, in a garden bed, meadow, or disturbed field [1]
2. A hairy stem and leaves that stay green in a rosette before the flower spike rises

What you can do:

1. Wear gloves when handling the plant, since all parts contain toxic compounds [3]
2. Dig out unwanted plants by hand, roots included, before they flower in May
3. Cut off flower spikes before seed capsules form to prevent self-seeding into nearby ground
4. Bag and trash pulled plants and cut flower spikes rather than composting them
5. Keep young children and pets away from the plant, and never mistake its leaves for an edible garden green
6. Natural-area crews: remove any naturalized plants found in meadows or disturbed ground away from garden settings, prioritizing removal before the May?June bloom to prevent seed spread

When to call a professional:

1. Suspected ingestion by a person, pet, or livestock ? this is a medical or veterinary emergency, not a plant-management question, so contact poison control or a veterinarian immediately
2. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Native Plant Trust Go Botany. Digitalis grandiflora (yellow foxglove). gobotany.nativeplanttrust.org
2. Integrated Taxonomic Information System (ITIS). Digitalis grandiflora Mill. itis.gov
3. Negroni MS, Marengo A, Caruso D, et al. (2019). "A Case Report of Accidental Intoxication following Ingestion of Foxglove Confused with Borage: High Digoxinemia without Major Complications." Case Reports in Cardiology 2019:9707428. pmc.ncbi.nlm.nih.gov

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