Threadleaf Penstemon Plant Care
Penstemon filiformis (D.D.Keck) D.D.Keck
Updated · Sources · How we source care data
Penstemon filiformis is an uncommon species of Penstemon known by the common name threadleaf penstemon. It is endemic to the Klamath Mountains of northern California, where it grows in forest and woodland, often on serpentine soils.
Every 7–10 days
Full sun to part shade
50–80°F
40–70%
At a glance
How do you care for Threadleaf Penstemon?
Water Threadleaf 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.
Where Is the Threadleaf Penstemon Native To?
What Is the Threadleaf Penstemon?
Threadleaf Penstemon (Penstemon filiformis) belongs to the Plantaginaceae family within the Penstemon genus. Threadleaf Penstemon is native to the Klamath Mountains of northern California.
Threadleaf Penstemon displays an upright, clumping perennial growth habit, reaching up to 2 ft tall with a spread of approximately 1.5 ft. Threadleaf Penstemon produces tubular flowers in shades of red, pink, purple, or blue.
Leaf size: approximately 4 inches.
How Often Should You Water a Threadleaf Penstemon?
Penstemon filiformis 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 Threadleaf Penstemon Need?
Threadleaf Penstemon thrives in full sun to part shade.
Light Requirement
Full sun to part shade
What Temperature and Humidity Does the Threadleaf Penstemon Prefer?
Penstemon filiformis grows best at temperatures of 50–80°F. Threadleaf Penstemon prefers humidity levels of 40–70%.
Temperature
50–80°F
Humidity
40–70%
What Soil Mix Works Best for a Threadleaf Penstemon?
Well-draining sandy loam with added organic matter for moisture retention. Good drainage is essential for Threadleaf Penstemon to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Threadleaf Penstemon?
Feed Threadleaf 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 Threadleaf 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 Threadleaf Penstemon?
Threadleaf Penstemon can be propagated through seeds, stem cuttings. Similar propagation techniques also apply to foxglove beardtongue plant care, which shares the same genus.
Is the Threadleaf Penstemon Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Threadleaf 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 Threadleaf Penstemon?
Threadleaf 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 Threadleaf Penstemon Need?
Threadleaf Penstemon grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Threadleaf Penstemon is native to the Klamath Mountains of northern California. In cooler regions, grow Threadleaf Penstemon as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Threadleaf 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.
Threadleaf Penstemon thrives in bright light and direct sun — see other bright-light plants.
More Penstemon Species
Other Penstemon species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Penstemon filiformis (D.D.Keck) D.D.Keck, family Plantaginaceae (first published in Ill. Fl. Pacific States 3: 761 (1951)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Threadleaf 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.
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