By Dr. Leonard Perry Extension Greenhouse and Nursery Crops Specialist University of Vermont
“Extremeophiles” is a term applied to microorganisms that tolerate some of the harshest conditions on earth. It’s an appropriate name for perennials that tolerate the extreme climate cycles in moisture and temperature that have been common in the north country in recent years. Let me give you some examples.
What I like to define as extreme perennials are those that aren’t fussy about temperature and survive just as well in moderate temperatures as they do in extreme heat. They prefer a sunny location, but will tolerate weeds. Most become established easily and are hardy between USDA zones 3 and 8. While not all are suitable for all conditions, you should be able to pick a few from this list that will work in your garden. All of these provide bloom later in the growing season.
First, let me suggest any of the perennial geraniums, which are quite variable in hardiness. The Siberian Cranesbill, Geranium wlassovianum (pronounce “vlass-so-vee-a’-num”) begins bloom later in summer and continues throughout the season. It is one of the larger leaved geraniums but doesn’t wilt readily during drought as do others such as the macrorrhizum cultivars. The purple flowers appear on the mound of leaves about three feet across. During drought and autumn the foliage turns purplish.
Hostas, also called Plantain Lily or Funkia, do quite well in shade, tolerating moist or dry conditions. Many can be grown in sun in the north if given sufficient moisture. There are hundreds of cultivars, from one to four feet across, with blue to green to gold or variegated leaves. Some even may have attractive or fragrant flower spikes later in the summer. This genus is one of the most foolproof and requires the least maintenance. The only real problem may be slugs chewing leaves if it is too wet and there is poor air circulation.
The other four selections I recommend are ornamental grasses, a group deserving wider use especially in the north. No, these aren’t the grasses you mow. No, they don’t have colorful flowers, but yes, they do have attractive foliage and some flowers. No, not all grasses are hardy, but yes, many are quite hardy in the north or south.
The sedges (Carex genus) aren’t really grasses, but since they look like short ones (usually one to two feet tall), they are grouped with them. Most tolerate hot or cool, dry or wet, and sun or shade. Some have variegated foliage and may be marginally hardy, like ‘Ice Dance.’ One of my favorites forms nice low clumps of waxy blue foliage (glauca species).
The Eulalia grass (Miscanthus), depending on species and location, may be invasive or not hardy. Another species (purpurascens) forms clumps about five feet high. It is hardy and, at least in the north, doesn’t have enough of a season to set seed. It doesn’t really have purple foliage but turns reddish in the fall. It’s another carefree perennial.
Another upright grass, which is generally quite hardy, is the Feather Reed Grass (Calamagrostis). It may get to be four to six feet high and gradually forms large clumps a foot or two across. From mid-season through winter it has tan spikes (the grass flowers). One selection, ‘Karl Foerster,’ is a Perennial Plant of the Year selection for 2002.
The Moor Grass (Molinia) is a bit different from most ornamental grasses, forming mounds of finely textured leaves about two feet high and two feet across. From these arise tall stalks from four to eight feet high, depending on cultivar, of finely textured “flowers.” It’s another carefree perennial grass, good in masses or for its fine texture in borders. It is hardy and tolerant of “extreme” conditions, making it an ideal choice for northern New England.