University of Vermont Extension
Department of Plant and Soil Science
Fall News
Article
Salt Tolerant Perennials
Dr. Leonard Perry
Extension Professor, University of Vermont
With winter in the north comes salt
applied to roads and walks to melt snow and ice. Such salt can damage
the roots of nearby
perennial plants. There are several
herbaceous perennials fairly tolerant of winter road salt.
If you’ve ever tried to get salt out of a
salt shaker during humid weather, you’ve seen the affinity of salt for
water
and moisture. The same principle applies
in soils, with the salt pulling moisture away from the roots. This
results in root “dessication” or drying
out.
Another way perennials can be injured is
from the sodium and chloride ions, which make up salt, separating.
Chloride ions are readily absorbed by the
roots, transported to the leaves, and accumulate there to toxic levels.
It is
these toxic levels that cause the characteristic marginal leaf scorch
seen
during the growing season.
If salts build up in pots, growers can flush
them out by heavy watering. This is not
so easily done in soils. Instead, if on
your own property, use “plant safe” products such as those deicing
materials
derived from magnesium or calcium chloride, or a mix of these with
kitty litter
(not the sawdust kind which doesn’t provide traction).
Another option, and perhaps the only one
along roads, is to plant perennials tolerant of high salt levels. At
least with perennials, that die back to
the ground each winter, you don’t need to be concerned with salt spray
to
foliage as you do with woody plants and evergreens.
Some of the hardy (generally USDA zone 5
or colder) perennials I’ve found listed as highly salt tolerant include
some
columbine and pinks (Dianthus),
bearberry, common wood aster, daylily species and hybrids, bird’s foot
trefoil,
seaside goldenrod (Solidago sempervirens),
and barren strawberry (Waldsteinia). The latter is a great low
groundcover for dry
shade, quite underutilized. Its yellow
flowers in early summer resemble those of strawberry plants. ‘Karl
Foerster’ reed grass, blue lyme grass,
maiden grass (Miscanthus), muhly
grass, sand cordgrass, and little
bluestem are ornamental grasses reported salt tolerant.
Hardy perennials with at least some salt
tolerance include silver mound artemisia, butterfly weed, candytuft,
foxglove,
sea holly, peony, baby’s breath, tall phlox, creeping phlox,
bellflower, Lenten
rose, coralbells, bearded iris, evening primrose, ‘Autumn Joy’ sedum,
hens and
chicks, Russian sage, Prairie mallow, soapweed, sea thrift (Armeria),
yarrow, and yucca. ‘Elijah’ blue fescue is a low ornamental
grass with some salt tolerance, as is ribbon grass (Phalaris), panic
grass (Panicum),
blue oat grass, and fountain grass (Pennisetum). Keep in mind the
latter can be quite root
invasive so needs proper placement.
Don’t plant ribbon grass where it will crowd out other desirable
plants,
or where root pieces can wash with rains through streams and ditches to
colonize elsewhere. The least tolerant
hardy perennials for salt include purple coneflower, hosta, narcissus,
and
thyme.
These are some of the more commonly
reported salt tolerant perennials, with others possible. A good
starting point is the seaside list,
one of the many useful lists, from Van Berkum wholesale perennial
nursery (vanberkumnursery.com/charts.html). There are of course many
other salt tolerant
perennials for warmer climates.
Return to Perry's Perennial
Pages, Articles 