One of my long-term projects is to find out which penstemons will do well in Kansas. I’ve got around twenty species planted in various parts of the yard, many of which are coming into bloom now. The Kansas natives such as Penstemon cobaea, above, have done very well. In general, most species I’ve tried have been easy and haven’t needed attention beyond weeding and occasional watering during dry spells.
P. wrightii is native to west Texas, a place much drier than Kansas. Surprisingly, all the rain from last year’s freakishly wet summer didn’t bother it at all, nor did 0℉ in January or 12℉ in March. It’s been blooming for three weeks now, and it should continue for at least one and possibly two weeks more. Although the individual flowers aren’t large, there are a lot of them, and the color is vivid.
P. clutei is found near the Sunset Crater in Arizona, but it does well in many places, including Kansas.
P. pseudospectabilis is found throughout the southwest. Unfortunately, my plant is at the back of the garden and the flowers are facing into my neighbor’s yard, which makes taking pictures awkward.
Penstemon is a particularly good genus for blue. P. alpinus, or , or P. glaber var. alpinus, from Wyoming and Colorado, has been easy so far, but it tends to be floppy.
The color of blue penstemons varies from plant to plant, and can also vary from year to year on the same plant. Generally, the more sun a plant receives, the bluer its flowers. Last year P. azureus, above, was definitely blue, but this year it’s purple. P. heterophyllus, below, is supposed to be blue, but this one is mostly lavender. Perhaps next year it will be blue. Both species are from California; P. azureus ranges up to southern Oregon.
P. strictus, the “Rocky Mountain Penstemon,” grows throughout the Rocky Mountain states. It’s easy and tough, and will likely grow anywhere that the climate isn’t too extreme.
Notes on Penstemons
The genus Penstemon used to be in the Scrophulariaceae family, along with its relatives snapdragons and foxgloves. However, taxonomists couldn’t leave well enough alone, and it has recently been lumped into the Plantaginaceae. It’s the largest genus of flowering plants endemic to North America, with species found from Alaska to Guatemala and in every state of the USA except Hawaii. The most intensely red and blue species are generally from the western states. Utah has the greatest number of native species.
My experience has been that most of the available species aren’t difficult to grow as long as you avoid ones that come from radically different climates than your own. Here in Kansas, I’ve had good luck with genera from hot areas of the southwest and low elevations in the mountains. Alpine species are difficult. If your summers are cool and damp, your choices will be different.
While plants of some species are available1, most of the interesting penstemons need to be grown from seed2. With a few exceptions, the seeds won’t germinate without experiencing winter chilling. You can sow them outdoors in the fall if you have a secure, protected spot, or you can “stratify” them in your refrigerator. I use the “coffee filter” method described here. Germination rates vary, depending on the variety and the freshness of the seed, and there are always a few pots in which nothing sprouts. Once up, the seedlings grow steadily. Most species bloom in their second year.
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I was curious just how much botany AI understands, so I told Z-Image Turbo to make a picture of P. strictus. It gets partial credit; it’s reasonably close on the flower color and general habit of the plant, but the flower shape is wrong and the real plant is much more upright with narrower stems.
Notes
- High Country Gardens has been a reliable source
- My primary sources for penstemon seeds are Alplains and the American Penstemon Society‘s annual seed exchange.