University of Vermont Extension
Department of Plant and Soil Science
GARDENING IN A CHANGING CLIMATE
Dr. Leonard Perry, Extension Professor
University of Vermont
Just looking at the facts from scientists (www.epa.gov/climatechange), we
see that our winters are becoming milder, summers warmer, our growing
seasons longer, and greater variability when spring comes, but often coming
quite early. The precipitation trend is toward more in the winter but
of wet snow or even mixed events, and more heavy rain events in summer yet
with periods of drought. How is the gardener to cope? With
proper planning and plant choices, gardeners can make their gardens and
landscapes better adapted to weather changes, extremes, and the impact of
these on pests and diseases.
Dealing with Drought. These tips are particularly important if
you have soils that tend to dry out quickly during drought periods (sandy
loam) or bake hard (clay loam).
--Cultivate the soil deeply prior to planting, and work in plenty of organic
matter. The latter, such as compost, rotted manure, or peat moss
improve soil structure and water retention.
--Apply sufficient and appropriate fertilizer (according to a soil test),
but not too much. Too much leads to excess top growth, more
susceptible to drought and plants needing more water, not less.
Adequate fertilizer keeps plants growing well, and thus more tolerant of
--Chose plants with gray-green or silvery leaves. These tend to
reflect light and not dry out as quickly. Lamb’s ears, catmint, lavender
(where hardy), Russian sage, Silver Mound and other artemsias are examples
with silvery leaves. Ornamental grasses (for sun) with their spiky
leaves, or plants with waxy-coated leaves like some hostas (for shade), also
tolerate drought. Plants with
deep tap roots such as false indigo or Baptisia, balloon flower, butterfly
weed, poppies, and thistle better withstand drought than those with more
shallow, fibrous roots.
--Plant small. Plants that grow in a dry soil or site from an early
age will be more adapted to it.
--Mulch. Use organic materials such as bark chips or straw, 2 or 3
inches thick, to help conserve water and prevent the soil from
crusting. Around shrubs or trees that don’t spread as do many
perennials, permeable weed fabric mulches can be used with a thin layer of
bark on top.
--Install irrigation. Drip or soaker hoses are most conservative of
water. Half or more of the water from overhead sprinklers may be lost
--Water deeply. Unless for a seedbed just getting started, less
frequent but deeper watering (the top foot of soil) will encourage deeper
rooting which is more resistant to drought.
--Create ponds or water features to provide water to wildlife during
Too much water. These tips are particularly important if you
have soils or areas that tend to stay wet and soggy after downpours, or that
even may flood periodically.
--Choose tolerant plants for these areas. While few plants tolerate
permanently wet soils (except water and bog plants), Siberian iris, joe pye,
turtlehead, foxglove, ligularia (shade) and astilbe (shade) are some
perennials for wet soils, the latter two preferring not to dry out.
River birch, hackberry, green ash, swamp white oak, pin oak, willow, and
bald cypress are some trees for wet soils. Red chokeberry, summersweet
clethra, shrub dogwood, winterberry, and purpleosier willow are some shrubs
for wet soils.
--Use raised beds to grow above the wet soil, the longer the soils stays wet
the higher the bed (one foot or more). Grow shrubs or trees on slight
--Incorporate drain pipes or tiles to help remove water from areas if they
are the only choices for planting, and there is somewhere to redirect excess
--Reduce stormwater runoff from paved surfaces by using permeable pavers,
just space between solid pavers, or permeable “paving gravel” and bark mulch
for lower traffic areas.
--Create rain gardens to hold water from heavy rain events, allowing it to
percolate back into the soil over time. Larger and longer areas,
called vegetated swales, help treat and reduce water flow as it passes
through these areas.
--Use rain barrels or similar holding tanks to collect water during heavy
rains to use later. Many prefer not to use such runoff from roofs on edible
--Consider installing green roofs on sheds or garages to slow and reduce
--Avoid working on soils while wet, as this will destroy soil structure.
--Avoid removing too much vegetation from slopes, to avoid erosion during
--After a flood, once the soil is somewhat dry, remove it from beds and
around plants, wearing gloves if pollutants from elsewhere may have been
brought in. Watch for signs of nutrient deficiency, fertilizing as
appropriate or using foliar feeding (watering fertilizer on leaves).
For edible plants, destroy greens, those eaten raw, and any others near to
harvest. Wait until next season to grow crops on that site that are to
be cooked. Wait two seasons to grow salad crops or those to be eaten
raw, in order to allow potential diseases to leave the soil.
Coping with Cold. Even if some winters are warmer, there may be
cold spells with little or no snow cover, causing soil temperatures to
drop. While, on average, winters may show a warming trend, some may
drop lower than normal. Extremes may be the new norm. Wide temperature
swings, particularly in fall and spring when plants aren’t fully hardened,
may cause damage. Choosing plants adapted over a range of wide climate
zones is a starting point.
--Mulch. Only a couple inches of mulch can trap ground heat, keeping
roots warmer and preventing rapid temperature swings in soil temperature
(the key for perennials).
--Keep woody plants, particularly broad-leaf evergreens such as
rhododendrons, well-watered prior to winter. This will help them
survive drought and long winters, and drying winds.
--Tender plants, such as roses, can be mounded with straw (if not rodent
issues), or otherwise with compost, soil or even manure, to protect bases
and graft unions.
--Use protected microclimates on a property for more tender plants such as
some magnolias, butterfly bush, less hardy rose varieties, and some
--Even if the climate is warmer overall by a hardiness zone or more, there
can still be extremes some winters. Or, while a particular winter may
be warmer on average, it could still have extreme cold episodes, killing
more sensitive plants and buds. Continuing to plant the most hardy
varieties will provide some protection again such extremes, as well as
abnormal late frosts.
--If a shrub is special, or with stems prone to breaking under ice, protect
it with a wooden structure or teepee, or even wrapped in burlap (not plastic
that gets too hot on sunny days).
Potential pests. While human activity is a main factor helping
to introduce exotic and invasive and destructive pests, the climate is a key
factor in helping them to establish. Climate affects the breeding
season, length and number of life cycles, foraging times, food availability
and availability of predators such as birds, and of course
overwintering. Get in the habit of at least weekly scouting your
plants for new pests. Then learn what they are (check the internet,
local trained garden professionals, or your state Extension system). Decide
the level of tolerance and, if controls are needed, start with least toxic
and non-chemical ones if available.
Dealing with disease. Drier summers would mean less diseases
that like water, such as downy mildew, leaf blights such as tomato and
potato, rose black spot, and fruit scabs. Powdery mildew, however,
does just fine in drought and likes drought-stressed plants. Warmer
and wetter winters, however, could lead to more potato leaf blight and root
rots. New diseases to the North from southern climates might establish
if winters are warmer. Make sure to buy disease-free plants, and
disease-resistant cultivars if available.
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