Extreme Perennials – Late Season


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.

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