Endless Summer
Beard Tongues Keep On Giving.
By Rachel Foster 5/11/06

There are few perennials as generous with bloom as the hybrid penstemons that are known as "border" or "garden" penstemons. If you have a sunny garden with a limited amount of space, you can hardly afford not to grow them. These showy garden varieties of mixed parentage grow to two feet or more, with foxglove-like flowers as much as two inches long in shades of white, pink, crimson, lavender and purple. (A hairy structure in the flower's throat gives penstemons the common name of beard tongue.) These hybrids tend to be easier to grow in ordinary garden soil than wild penstemon species, which are best suited for rock gardens, gravel gardens or impeccably drained slopes. Border penstemons are not especially long-lived, but they develop fast from inexpensive 4-inch plants and bloom until frost.
In suitable conditions, border penstemons will live for several years. They are easy to propagate if you get tired of buying new ones. Books suggest taking stem-tip cuttings in late summer or early autumn. The cuttings should root in two weeks at 59òF. Protect cuttings through their first winter in a cool greenhouse or cold frame (winter wet is a greater threat than cold). If you are not set up to over-winter late summer cuttings, you can try my simple method: Cut rooted pieces, with small leafy shoots attached, from the base of the plants in early spring and pot them up. Mulching plants lightly in fall with a mixture of grit and compost ensures that these basal "cuttings" will have well-developed roots.
Established border penstemons have relatively low water requirements, so you can mix them with artemisia, catnip, phormium and other drought-tolerant plants. Full sun yields best flowering and a more compact habit. Some gardeners complain that penstemons are floppy. It helps to give them only moderate amounts of fertilizer and water and snip off exhausted flowering stems throughout the summer. You can also support plants early in the season with twiggy sticks stuck in the ground, or those horizontal grid supports that vertical stems will grow through. I don't have very high standards of neatness and simply count on neighboring plants to hold up my penstemons.
Some favorite, hardy varieties include Apple Blossom, Thorne (both white with pink highlights), deep red Garnet, Holly's White and purple Sour Grapes. Like some other plants that remain evergreen through an average winter, maintenance of penstemons provides a bit of a conundrum: to cut or not to cut? My rule of thumb is to trim away any dead stems tips no earlier than early or mid-March. Then, when the weather really warms up and the plants appear to be growing actively, I cut off all of last year's stems just above the new shoots emerging near the base.
Most of the roughly 250 species of penstemon occur in western North America. Those from mountainous or arid parts can be difficult to grow in western Oregon unless you can provide perfectly drained soil. If you have the right conditions, try tall, scarlet-flowered Penstemon barbatus and P. eatonii. Both are elegant hummingbird magnets that bloom and bloom. Low-growing P. pinifolius, with needle-like foliage and bright red or yellow tubular flowers, is almost continuously in bloom. Rock-hugging species from the Cascade mountains, such as P. rupicola and P. newberryi, have short but spectacular flower displays. I grow them both with dwarf evergreens in big bowls of gritty soil.
Penstemon heterophyllus, Catherine de la Mare, has been a happy surprise. This is a low, semi-shrubby plant with spikes of small blue flowers. It has a rock-garden look to it, but I have found it easy to grow in ordinary garden soil and quite long-lived and vigorous. It's a perfect plant to drape over a rock border or the edge of a retaining wall.