University of Vermont Extension
Department of Plant and Soil Science
Anytime News
Article
SHADE IN THE GARDEN
Dr. Leonard Perry, Extension Professor
University of Vermont
Hostas, spurge (Pachysandra), and
rhododendron are some of great choices you have for shady gardens.
Before choosing any plants for shade, it’s
important to realize a few facts about this environmental habitat that
will
help you grow more plants there more successfully.
Shade is not all the same. Soil moisture levels can vary from moist to
dry. Ferns and astilbe like moist shade
and wont grow well in dry shade, while hostas and barren strawberry
(Waldsteinia)
will. A wet area, water seepage from the
ground, or a stream, can create a moist woodland. Areas under large
trees can be quite dry from
the tree roots taking up most available soil moisture. In my own
yard, soil moisture under a large
maple often begins the season around 70 percent, similar to my full sun
beds
away from any trees. By midsummer,
especially if little rain, the tree area can drop to 35 percent
moisture, with little
drop in the loamy sun beds.
Whether a plant “prefers” or merely
“tolerates” a certain soil moisture is another aspect you don’t usually
see
mentioned. Lungworts (Pulmonaria),
for instance, prefer a moist soil but will tolerate some dryness even
though
they wilt. Coralbells prefer a drier
soil, but will tolerate some moisture.
The third aspect relates to soil moisture as well, that being the age
of
the plant. A plant such as lungwort may
not tolerate much drought when young, but may when mature.
Of course light is the main factor with
shade, and you may see various terms to describe the amount of light a
plant
“needs”. As with soil moisture, the
terms “prefer” and “tolerate” apply
here too. Many sun plants may tolerate
some shade, just bloom less, and perhaps be more straggly
and need staking. On the other hand,
some shade plants (especially in the north with cooler summers) may
tolerate
full sun IF sufficient soil moisture is maintained.
Here are some terms you may see referring
to shade, from most dark to most light.
--
Full shade occurs when no direct sunlight reaches plants, and there
isn’t much
reflected light either. This is what you
find underneath dense tree canopies, such as under a large deciduous
(loses its
leaves in winter) maple or oak tree, or evergreen pine.
--
Summer shade is a variation of full shade, and occurs under deciduous
trees
that are bare in spring allowing light in, and fully leafed out in
summer
allowing no direct light. This is what you find in many northern mature
woodlands, and favors spring wildflowers whose lives are programmed to
maximize
on this fleeting spring sunlight.
--
Bright shade is a term you see less often, and occurs where little
direct light
reaches plants but where they do get much reflected or indirect light.
This might be found next to a bright,
south-facing wall of a building. You can
create bright shade by removing lower limbs of trees and shrubs, or
thinning
them out. Consider this approach if you
have too much dense shade.
--Dappled
shade occurs when spots of light appear for a short period, then
disappear as
the sun moves across the sky. It is what
you find if walking in a mixed woodland.
--
Part shade occurs when direct light reaches plants for perhaps half a
day, four
to five hours. This is what you find on
the edges of woodlands or in front of tree plantings. It may be
afternoon or morning sun, which may
make a difference with a few plants (afternoon sun being hotter).
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