Slender Penstemon Plant Care
Penstemon tenuis Small
Updated · Sources · How we source care data
Penstemon tenuis is a species of flowering plant in the plantain family known by the common names sharpsepal beardtongue and gulf coast beardtongue. It is endemic to Texas, Louisiana, Mississippi, and Arkansas in the United States where it is found in open, damp areas in alluvial soil.
Every 7–10 days
Full sun to part shade
50–80°F
40–70%
At a glance
How do you care for Slender Penstemon?
Water Slender Penstemon every 7–10 days, letting the top layer of soil dry out between waterings, and give it full sun to part shade. It prefers temperatures of 50–80°F (10–27°C) and 40–70% humidity. Fertilize it every 6 months during the growing season.
What Is the Slender Penstemon?
Slender Penstemon (Penstemon tenuis) belongs to the Plantaginaceae family within the Penstemon genus. Slender Penstemon is native to open, damp areas in alluvial soil.
Slender Penstemon displays an upright, clumping perennial growth habit, reaching up to 2 ft tall with a spread of approximately 1.5 ft. Slender Penstemon produces tubular flowers in shades of red, pink, purple, or blue.
Leaf size: approximately 4 inches.
How Often Should You Water a Slender Penstemon?
Penstemon tenuis requires watering every 7–10 days. Allow the top layer of soil to dry between waterings to prevent root rot. Reduce watering frequency during winter when growth slows.
Watering Frequency
Every 7–10 days
Let soil partially dry between waterings
What Light Does the Slender Penstemon Need?
Slender Penstemon thrives in full sun to part shade.
Light Requirement
Full sun to part shade
What Temperature and Humidity Does the Slender Penstemon Prefer?
Penstemon tenuis grows best at temperatures of 50–80°F. Slender Penstemon prefers humidity levels of 40–70%.
Temperature
50–80°F
Humidity
40–70%
What Soil Mix Works Best for a Slender Penstemon?
Well-draining sandy loam with added organic matter for moisture retention. Good drainage is essential for Slender Penstemon to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Slender Penstemon?
Feed Slender Penstemon every 6 months during the growing season (spring and summer) with a balanced fertilizer diluted to the strength on the label.
Pause feeding in autumn and winter, when growth slows, and never fertilize dry soil — water first.
Fertilizing
Every 6 months
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
How Do You Repot a Slender Penstemon?
Repot every 2-3 years in early spring. Choose a pot one size larger than the current container, and ensure it has drainage holes to allow excess water to escape.
How Do You Propagate a Slender Penstemon?
Slender Penstemon can be propagated through seeds, stem cuttings. Similar propagation techniques also apply to rocky mountain penstemon plant care, which shares the same genus.
Is the Slender Penstemon Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Slender Penstemon, so we can't confirm whether it is safe for cats and dogs. Keep pets from chewing it as a precaution.
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Slender Penstemon?
Slender Penstemon is susceptible to aphids, spider mites, powdery mildew. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
What USDA Hardiness Zone Does the Slender Penstemon Need?
Slender Penstemon grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Slender Penstemon is native to open, damp areas in alluvial soil. In cooler regions, grow Slender Penstemon as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Slender Penstemon is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Penstemon genus — compare its care with other Penstemon species on PlantoScan.
Penstemon is part of the Plantaginaceae plant family — browse all Plantaginaceae genera and species.
Slender Penstemon thrives in bright light and direct sun — see other bright-light plants.
Related Plant Care Guides
Closely related plants with similar care requirements:
Sources
- Scientific name & taxonomy: Penstemon tenuis Small, family Plantaginaceae (first published in Fl. S.E. U.S. : 1061 (1903)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Slender Penstemon, so we can't confirm whether it is safe for cats and dogs. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Hardiness zone: USDA Zone 12a, calculated from the plant's minimum temperature.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
Identify Plants Like the
Slender Penstemon Instantly
Scan any plant with your phone camera and get instant ID, care tips, water and fertilizer reminders, and health checks — all in one app.
Free
to download
iOS & Android
platforms
Light & dark
mode
100,000+
species