Penstemon Flowers – Partly Evergreen Perennials or Deciduous
Penstemons, also called beardtongues, are a large group of flowering plants with bright, tube-shaped blossoms that hummingbirds and bees love. There are roughly 250 species, and almost all of them are native to North America, with just one species found in northeastern Asia.
Scientific Classification & Quick Facts
| Common name | Penstemon |
| Scientific name | Penstemon |
| Kingdom | Plantae |
| Phylum | Tracheophyta |
| Class | Magnoliopsida |
| Order | Lamiales |
| Family | Plantaginaceae |
| Type | Perennial, shrub or sub-shrub; also called beardtongue |
| Habitat | Moist forests, dry areas and alpine zones |
| Native range | North America |
| Flowering season | Late spring or late summer |
| Height | 10 cm to 3 m |
| Special feature | Sterile stamen sticks out like a tongue |
Where Penstemons Grow
Penstemons once belonged to the figwort family (Scrophulariaceae). Modern DNA studies moved them into the much larger plantain family, Plantaginaceae, which also includes snapdragons and foxgloves.
In the wild, penstemons grow in an amazing range of places across North America, from deserts and dry prairies to open woodlands, rocky slopes and high mountain meadows above the tree line. Many species are adapted to one particular area, so some are common while others are rare and hard to find.
What Penstemons Look Like
Photo by: Stan Shebs
Penstemon leaves grow in pairs, opposite each other on the stem. The flowers are tubular with two “lips”: two lobes on top and three on the bottom. After flowering, the plant forms small capsules full of tiny seeds.
The most unusual part of a penstemon flower is the staminode. This is a sterile stamen, which means it does not make pollen. It sits in the throat of the flower, and in many species it is covered in hairs. When you look into the open flower, it can look like a mouth with a fuzzy tongue sticking out, which is how the plant got the name “beardtongue.”
Flower colors include red, pink, purple, blue, lavender and white. Red, narrow-tubed flowers are usually pollinated by hummingbirds, while wider blue and purple flowers tend to attract bees.
Most penstemons are perennials, which means they live for several years. Some keep part of their leaves through winter (semi-evergreen), some die back to the ground (deciduous), and a few are small woody shrubs. Depending on the species, they can be just a few inches tall or reach several feet.
How to Grow Penstemons at Home
Choosing a Spot
Photo by: Kurt Stüber
Penstemons are fairly low-maintenance once they settle in. The two most important things they need are full sun and excellent drainage. Many species grow naturally in dry, rocky or sandy places, and soggy soil quickly rots their roots, especially in winter.
If your garden has heavy clay, plant penstemons in a raised bed, on a slope or in a rock garden, and mix in grit or coarse sand to help water drain away. Rich, heavily fertilized soil is not necessary and can make plants floppy and short-lived.
Planting
Plant penstemons in spring, after the danger of hard frost has passed. Here are some simple steps:
- Space plants about 1 to 3 feet apart, depending on how big the variety grows, so air can move between them.
- Loosen the soil to a depth of about 12 inches and, if it is heavy, mix in grit or a small amount of compost.
- Dig a hole about twice as wide as the pot.
- Set the plant in the hole so the top of the root ball is level with the soil surface, then fill in around it and firm the soil gently.
- Water well. A thin layer of gravel around the base of the plant helps keep the crown dry.
In colder areas, planting near a sunny wall can give penstemons a little extra warmth and shelter. A light sprinkle of slow-release or organic fertilizer in spring is plenty; many wild species need no feeding at all.
Watering
Water young plants regularly during their first summer so the roots can grow deep. Once established, most penstemons are quite drought tolerant and only need a drink during long dry spells. Overwatering is a far more common problem than underwatering.
Flowering and Care After Blooming
Depending on the species, penstemons bloom anywhere from late spring to late summer. Once the first flowers fade, cut the flower stems back to just above a pair of healthy leaves. This “deadheading” often encourages a second, smaller round of flowers later in the season.
Many penstemons are short-lived and may only last a few years in the garden. You can keep them going by taking cuttings in late summer or by letting a few flowers set seed.
Penstemons as Cut Flowers
Photo by: Stan Shebs
Penstemons are mostly grown to brighten gardens and to feed pollinators, but their tall flower spikes can also be cut for a vase. They do not last as long as some florist flowers, but cutting stems when only the lower flowers are open helps them look fresh for several days.
Planting penstemons is a great way to bring hummingbirds, bees and butterflies to a sunny garden. Native species are especially valuable, because local wildlife has evolved to use them.
Penstemon FAQs
Why is penstemon called beardtongue?
Penstemon flowers have a sterile stamen, called a staminode. In some kinds it is hairy and sticks out of the flower like a bearded tongue.
How tall does penstemon grow?
It depends on the kind. Penstemons range from just 10 centimetres tall to as much as 3 metres.
Where does penstemon grow?
Penstemon is widespread in North America. It grows in moist forests, dry areas and high alpine zones.
When does penstemon bloom?
It depends on the species, but penstemons bloom in late spring or late summer. If you snip the stems after flowering, you may get a second flush of flowers.
How much water and sun does penstemon need?
Penstemons like bright sun and quick-draining soil. They can handle dry weather once settled, so avoid overwatering.
Randi Jones is the owner and founder of the Nature Gift Store, an online retailer specializing in nature-themed gifts, educational science projects, live animal nature kits and real butterfly artwork. A biology graduate who fell in love with insects, she founded the company in 2001 to make active learning about nature fun, accessible and engaging for children and adults. Her store offers real butterfly frames, home and garden decor and educational live animal kits, including ant farms, worm farms, tadpoles, ladybugs and hermit crabs, and she runs a bug museum in Washington featuring live animals like Eddie the Iguana alongside other reptiles and insects.
