An amazing genus of plants native to North America, penstemons make wonderful additions to the garden. The diversity of these plants is truly remarkable, with several hundred species available. From dwarf little alpine plants to prairie penstemons reaching up to 5 feet tall, there’s a height for every part of the garden. And that’s just the plant height—the leaves and blooms also come in many different shapes, colors, and sizes.
With a rainbow of colors to choose from, everyone can find a penstemon to love. The problem is narrowing down your choices! The beautiful spires of tubular blossoms add loads of color to the garden and are beloved by hummingbirds and butterflies alike. With such a wide variety of species and cultivars to choose from, you can have a penstemon blooming for almost the entire growing season. The blooms look stunning in a garden setting and make a wonderful addition to a cut flower arrangement.
Along with their bright blooms, many varieties of penstemon also have colorful foliage to add to the mix. Varieties like 'Husker Red' have burgundy foliage and add another level of interest to these already spectacular garden plants. Other varieties have glossy green or blue-gray foliage that looks good all season long.
Penstemon Care Must-Knows
Penstemons are tough perennials that can stand up to some pretty intense growing conditions. There are tiny alpine species that can grow in the cracks of rocks and stand up to extremely cold weather, while others grow in disturbed soils in prairie settings. No matter where they are growing, penstemons need extremely well-drained soils and will not tolerate wet soils, especially over the winter. The prairie-type penstemons are much more tolerant of standard garden soils, whereas the alpine types require very sharp drainage, similar to what is found in gravel gardens and even trough gardens. No matter what type of penstemon you plant, all perform well in fairly nutrient-poor soils. The plants tend to put out too much tender growth in rich soils.
Penstemons also need full sunlight to perform their best. Not only will this ensure that they put on quality blooms, but it will also prevent them from flopping. Full sun also prevents the possibility of powdery mildew from developing on the leaves of some of the tall varieties, especially in humid summers.
After the plants have bloomed, penstemons will produce copious amounts of seed. If you are hoping to have your penstemon plants freely seed around your garden, make sure to leave a few stalks on the plants so they can fully ripen and disperse. Otherwise, by removing spent blooms, you can sometimes encourage a second wave of flowers. In some types, the seedpods can also be ornamental and can be left on the plants for winter interest.
With hundreds of species available, there are constantly new penstemon varieties being produced. In many cases, new varieties tend to be improvements of older types, with larger blooms, more compact habits, or darker foliage. There is also work to create continuous-blooming annuals. There are already several on the market that boast extremely long blooming times, and a few that will bloom nonstop from spring until frost.
More Varieties of Penstemon
Penstemon barbatus has narrow spikes of two-lipped tubular flowers about 2 inches long in spring. The colors can be red, pink, carmine, or purple. The 8-inch lance-shape leaves have a whitish bloom. The plant can reach 3-6 feet tall. Zones 4-9
An even darker variety of the much loved 'Husker Red'. 'Dark Towers' holds on to the burgundy foliage throughout the summer, and blooms have more of a pink flush as well. Zones 3-8
Lavender blooms with white lips nod above dense green leaves on dwarf plants reaching 6 inches tall. Zones 3-9
Penstemon heterophyllus 'Electric Blue', just as its name implies, has flowers that glow with color. Notably drought-tolerant, the plant grows about 18 inches tall. Zones 6-9
Penstemon digitalis 'Husker Red' blooms in early to midsummer with loose spires of 1-inch tubular pink-flushed white flowers. The lance-shape deep maroon leaves are 4-5 inches long and arranged in a basal rosette. It grows about 2-1/2 feet tall. Zones 3-8
Penstemon Companion Plants
Lady's mantle looks great in the garden and in a vase. Its scalloped leaves catch rain or dewdrops, making them look dusted with jewels. The chartreuse flowers appear in playful, frothy clusters above the foliage. Lady's mantle is ideal for softening the edge of a shaded path or creating a groundcover in dappled shade.
Lamb's-ears is a top pick for a groundcover in a hot, baked spot. Its silver felted foliage quickly forms a dense, delightful mat. It also contrasts nicely with other foliage and most flowers, enhancing almost everything. Depending on the type and your growing conditions, it may self-sow freely to the point of becoming a bother. In hot, humid climates, lamb's-ears may "melt down" in summer, becoming brown and limp. A quite different but related plant, big betony is worth growing for its shade tolerance, dark green crumpled leaves, and bright purple spikes of whorled 1-inch flowers in late spring. Wood betony is similar but not as shade-tolerant.
Catmint is one of the toughest perennials you can grow. It's a proven performer during hot, dry weather, and the silvery foliage and blue flowers look great most of the season. Deadhead or cut back hard after the first flush of bloom to encourage more flowers. Average, well-drained soil is usually sufficient. Tall types may need gentle staking; it sometimes seeds freely. As you might guess from the common name, catmint is a favorite of cats. They'll often roll around in the plants in delight.