Penstemon
Penstemon is a flower in the Plantaginaceae family. It grows best in full sun with dry moisture, and is listed for USDA zones 4-9. Plants reach maturity about 102–138 days after planting and sit about 12 inches apart.
Varieties
1 from True Leaf Market · sorted by days to maturity▸Palmer's102–138 days
Non-GMO; Container; Perennial
120 Days to maturity. Penstemon palmeri. Palmer's Penstemon Seeds. Non-GMO, open-pollinated, Premium Quality Seeds, perennial. Growing Palmer's penstemon seeds this season is an effortless and vibrant way to splash some familiar summer color and fragrance into your home or garden. Palmer's seeds grow elegant penstemons bursting with fragrant "snapdragon-like" flower stalks. Makes an eye-catching mid-level planting in any flower bed. Palmer's penstemon seeds grow bold and brilliant flowers, promising butterflies and important pollinators to the garden all season long. Palmer's penstemon is easy to grow from seed, and its hardy and robust stalks are an essential seasonal twist to traditional snapdragon arrangements and centerpieces.
View on True Leaf Market ↗
Plant spacing
In a square-foot bed, space penstemon about 12 in apart — that fits 1 plant in each 1-foot square (1×1). Wider rows or containers space the same.
Plan your penstemon planting
Add penstemon to a free GardenDraft plan and get sow, transplant, and harvest dates computed for your ZIP code — with a drag-and-drop bed layout and reminders when it’s time to plant.
Start your free plan →At a glance
Growing timeline
Care & troubleshooting— extension-sourced, with citations
When to feed, prune & water
Harden off seedlings
ProtectionUnusual this time of year.
- Routine careGradually expose plants to the outdoors· every 1 days · ~2 wksstrong evidence — extension confidence
Starting about two weeks before transplanting, set seedlings outside in a sheltered, shady spot for a few hours and lengthen their time and sun exposure each day, avoiding windy days, to prevent transplant shock.
- Routine careEase back on water and transplant on a mild daystrong evidence — extension confidence
Water a little less during hardening (without letting plants wilt) to toughen growth, then transplant in late afternoon or on a cool, cloudy, calm day.
Something looks wrong?
Describe what you see on your penstemonand we'll rank the likely causes — most likely first, least-invasive fix first.
Powdery mildew
Diseasemoderate- CulturalImprove airflow + remove worst leavesstrong evidence — extension confidence
Cut out the most heavily coated leaves and thin for airflow; avoid wetting foliage late in the day.
- OrganicPotassium-bicarbonate or sulfur - label use only· every 1 wk · ~4 wksmoderate evidence — extension confidence
Apply a labeled potassium-bicarbonate or sulfur fungicide weekly per the label. No sulfur within 2 weeks of oil or in high heat.
Slugs & snails
Pestmoderate- CulturalTrap, hand-pick at night, reduce cover· every 2 days · ~3 wksstrong evidence — extension confidence
Pick at night with a flashlight, set shallow beer traps, water in the morning so soil dries by dusk, and clear damp hiding spots.
- OrganicIron-phosphate bait - label use only· every 1 wk · ~3 wksmoderate evidence — extension confidence
Scatter a labeled iron-phosphate slug bait sparingly per the label; it's pet- and wildlife-safer than metaldehyde.
Spider mites
Pestmoderate- CulturalHose down and raise humidity· every 3 days · ~2 wksstrong evidence — extension confidence
Mites thrive in hot, dry, dusty conditions. Spray foliage (especially undersides) with water to dislodge them and reduce dust.
- OrganicInsecticidal soap or horticultural oil - label use only· every 5 days · ~2 wksmoderate evidence — extension confidence
Apply to undersides per label; mites resist many products, so soaps/oils are preferred. Not in extreme heat.
Aphids
Pestlow- CulturalBlast off with water· every 3 days · ~2 wksstrong evidence — extension confidence
Knock colonies off with a strong jet of water in the morning; repeat every few days. Light infestations rarely need more.
- OrganicInsecticidal soap - label use only· every 1 wk · ~3 wksmoderate evidence — extension confidence
For persistent colonies apply insecticidal soap to undersides per label. Avoid open flowers.