Penstemons for the Cottage Garden

Penstemons are enjoying an increased visibility in American gardens.  With a little searching one can have penstemons in bloom almost any time of the growing season in most of the country.  Once the province of alpine & rock gardeners or European botanic gardens, they now show up with regularity in catalogs and garden centers.  Native only to the Americas, penstemons range from woody sub-shrubs to tough perennials and tender ones grown as annuals.  Penstemons evolved with bumblebees and hummingbirds as pollinators; adding these plants to your garden will increase your wildlife viewing as well.  Most states have native penstemons on their native plant lists, and most are adaptable far beyond their home range.  Favored for their blues, they also include candy pinks and bright reds.  Once thought of as short-lived and fussy, breeding & evaluation projects by Universities and individuals alike bring new garden worthy plants to market yearly.
 
I first noticed penstemons while hiking; teeny spikes of blue trumpets caught my eye and I had to find out what they were.  A little research showed me there were many kinds locally but they sounded difficult to please.  As an adult, I tried them anyway (that blue!) with fresh seed from exchanges and basic growing information from the Penstemon Society. Now I have beds full of different kinds and am delighted to report that they are not difficult to please if you keep in mind hardiness and soil preferences.

You're likely to encounter two main types at garden centers and in standard catalogs: named varieties of tender perennials such as 'Garnet' and 'Thorn', best wintered over indoors in areas with temps that go much below freezing, and barbatus hybrids ('Rondo', 'Cambridge', etc.) plus the foliage plant 'Husker Red' whose flowers are an afterthought.
The barbatus types are a very good place to start. Blooming in mid-summer in shades of red, pink, purple and blue, they are a bee's delight and good cut flowers. Cutting encourages side shoots to flower for a longer season. Given sun and good drainage, especially in winter, they will really add sparkle to the garden.
For blooms like those of the tender varieties, try growing gloxinioides/hyacinthoides hybrid annuals. These are actually tender perennials which reliably bloom as annuals from an early indoor sowing. At 2-3' in gorgeous hot colors & bicolors, they are a must in the cottage & cutting garden. Favorite colors can be easily propagated from cuttings which will root in a glass on the kitchen windowsill.

Once you have grown these, you'll want to experiment with more forms and colors. The Mexicali hybrids by Bruce Meyer of Washington State are infused with the hot color of the tender Mexican types but retain the hardiness of the Northern Rockies types. They are standout garden plants. Glossy slender foliage supports spikes of showy trumpets in pinks, reds, and purples with a very long bloom season, from mid-summer to early fall. Plants form short plump bushes, to 15-18" tall in flower. The foliage stays green nearly year-round here in Zone 4, and plants die back only to the snow-line here. Probably would be no die-back in Z5 or Z6.


Penstemons which switch easily from the alpine enthusiast's garden to the home garden include P. confertus (tender pale yellow flowers, colonizes in uncut lawns but also looks good with yellow foxgloves), P. procerus (mat-former with tiny flower spikes in electric blue, purples or white like a blue Thrift), P. fruticosus (small woody shrub to 8-12", large lavender flowers in early summer), P. ovatus (tall plants, big vase-like leaves centered on the stems and large spikes of blue to purple flowers: easy, good cut, and very showy); P. wilcoxii (slender plants with many spikes in lavender to light blue; winter foliage turns red.


Generally, penstemons want a toothy, somewhat rich soil with sharp drainage. Their winter crowns are subject to rot if too wet or neck-snapping if freeze-thawed too roughly. An autumn mulch of grit or small gravel around the necks will provide better drainage, protect from gnawing, and promote rooting of offsets. While many are drought-tolerant, especially the more southern-originating ones, they do need water when flowering. In the wild, they often have long root runs searching back up under the scree they are decorating, finding hidden water. Also generally they want full sun, though some will take a fair amount of shade: P. ovatus does, and so does P. 'Sharon', one of my own selections, with bright turquoise flowers.


Starting penstemons from seed can be a bit tricky though the annuals and barbatus need no special attention to germinate. To try the others, it is easiest to sow in pans with a light covering of grit, tag, water, and set out to germinate over the winter in a cold frame or with a window screen over them to moderate winter splash and restrain mice. Sprouting will begin in early spring and go through mid-summer, depending upon variety; prick out seedlings to small pots then move to blooming positions by late summer. Keep those seed pans a few years; what doesn't sprout the first year usually will the next, and some take longer. Penstemons hybridize easily in the open garden; keep your seed and soon you may have new treats to add to your next seed exchange.
Copyright 2001-2007 Judith Miller