Penstemon gloxinioides 'Sour Grapes' (Beardtongue) — Bushy, upright, semi-woody at the base

Overview

Penstemon gloxinioides 'Sour Grapes' is a bushy, upright, semi-woody at the base perennial in the genus Penstemon, part of the Plantaginaceae family, with semi-evergreen or evergreen; narrow, glossy, mid to dark green foliage. Penstemon gloxinioides 'Sour Grapes' grows best in full sun, and tolerates most soils and neutral to alkaline pH. Its UK hardiness is rated H3-H5.

About

Penstemon gloxinioides 'Sour Grapes' is a perennial penstemon forming upright, well-branched growth with a semi-woody base. It carries narrow, glossy mid to dark green leaves that remain semi-evergreen in mild winters. Flowering runs from June to September. Position it in full sun on light, fertile, free-draining soil and protect from winter wet.

About the genus

Penstemon, the beardtongues, is a large genus of roughly 280 species of flowering plants native to North America from northern Canada to Central America. It is the largest genus of flowering plants endemic to North America. As well as being the scientific name, penstemon is also widely used as a common name for all Penstemon species alongside beardtongues.

Wikipedia contributors, "Penstemon", CC BY-SA 4.0 — Penstemon

In the garden

A cultivar of the North American genus Penstemon, Penstemon gloxinioides 'Sour Grapes' is a perennial valued for its upright, well-branched habit and narrow glossy foliage that stays semi-evergreen where winters are mild. The plant produces its main display from June to September. As a member of the Plantaginaceae, it shares the genus’s tubular flowers and a semi-woody base set on multiple stems. Grow it in full sun on light, fertile, free-draining loam or sand; neutral to alkaline ground suits it best. Sites should be south- or west-facing and sheltered from prevailing winds, because winter wet is the common cause of losses. The stated hardiness range H3–H5 translates to borderline to hardy in UK terms: give plants shelter in colder or exposed gardens and ensure soil does not remain waterlogged over winter. Use it where a sunny, sheltered accent is needed—rock or gravel banks, the front of a warm border, or in a container that can be moved to cover in poor winters. Give attention to drainage when planting; in marginal H3 sites consider container culture or lifting vulnerable specimens before prolonged wet spells so the crown can be kept dry through winter.

Growing conditions

Best soil and position for Penstemon

Sunlight: Full sun
Soil type: Light, fertile, free-draining loam or sand
Soil pH: Neutral to alkaline
Soil moisture: Well drained; winter wet causes most losses
Aspect: South or west facing
Exposure: Sheltered
UK hardiness: H3-H5

Plant details

Penstemon gloxinioides 'Sour Grapes' size, habit and characteristics

Plant type: Perennial
Habit: Bushy, upright, semi-woody at the base
Foliage: Semi-evergreen or evergreen; narrow, glossy, mid to dark green

Care notes

Pruning and caring for Penstemon gloxinioides 'Sour Grapes'

Cultivation: Drainage and shelter decide whether a penstemon is perennial or annual in your garden. Plant in spring rather than autumn so the roots establish before winter, and leave the top growth standing until spring as crown protection. Regular deadheading is what sustains the extraordinarily long season. Given the modest hardiness of most cultivars, taking cuttings every summer is sensible insurance.
Pruning: Leave stems intact over winter, then cut back to low healthy buds in mid-spring once frosts have passed. Deadhead continuously through summer, cutting spent spikes to a side shoot.
Propagation: Semi-ripe cuttings taken in late summer root quickly and are the standard method - and the usual replacement for winter losses. Species can be raised from seed.
Pest resistance: Slugs take young spring shoots; capsid bug and eelworm occur but are uncommon.
Disease resistance: Powdery mildew and leaf spot appear on crowded plants. Root rot follows winter waterlogging.

Frequently asked questions

How do I grow Penstemon gloxinioides 'Sour Grapes'?

Drainage and shelter decide whether a penstemon is perennial or annual in your garden. Plant in spring rather than autumn so the roots establish before winter, and leave the top growth standing until spring as crown protection. Regular deadheading is what sustains the extraordinarily long season. Given the modest hardiness of most cultivars, taking cuttings every summer is sensible insurance.

Where is the best place to plant Penstemon gloxinioides 'Sour Grapes'?

Penstemon gloxinioides 'Sour Grapes' prefers full sun. It suits sheltered positions.

What soil does Penstemon gloxinioides 'Sour Grapes' need?

Penstemon gloxinioides 'Sour Grapes' is adaptable and grows happily in most soil types, including light, fertile and free-draining loam or sand. It prefers neutral to alkaline soil. Aim for soil that stays well drained; winter wet causes most losses.

How do I prune Penstemon gloxinioides 'Sour Grapes'?

Leave stems intact over winter, then cut back to low healthy buds in mid-spring once frosts have passed. Deadhead continuously through summer, cutting spent spikes to a side shoot.

Is Penstemon gloxinioides 'Sour Grapes' hardy in the UK?

Penstemon gloxinioides 'Sour Grapes' has an RHS hardiness rating of H3, meaning it is half-hardy, tolerating -5 to 1°C, and may need winter protection in colder areas.

How do I propagate Penstemon gloxinioides 'Sour Grapes'?

Semi-ripe cuttings taken in late summer root quickly and are the standard method - and the usual replacement for winter losses. Species can be raised from seed.

More in the Penstemon genus

Browse all Penstemon →