Precipitation events (heavy rains) have become stronger, and more
frequent. The Northeast led the country with a 71 percent
increase in the most intense heavy rains from 1958 to 2012
(glisa.umich.edu/climate). The Midwest was second, with a 37
percent increase. During these heavy rains, since 1991 in these
regions over 30 percent more rain has fallen that during such
rains between 1901 and 1960 (nca2014.globalchange.gov/report).
The amount of the country experiencing extreme single-day rains
has increased from 10 percent of the land area in 1910 to around
18 percent now (www.epa.gov/climate-indicators). These are only
a few of the many studies illustrating that we’re now having to
deal with more water than in the past.
Projections show that by the end of the century we may see 7 to
14 percent greater rain and snow, the higher figure under higher
emissions. Yet, at the same time, we’ll likely see more
short-term droughts between rainy periods—another extreme to deal
Much of this precipitation increase is predicted to occur in
winter, ranging from 11 to 30 percent more than now. More rain or
mixed precipitation and less snow is predicted for winters, which
will influence overwintering of perennials, among other impacts.
This loss could be one quarter to one half of our current
snow-covered days. Snow is one of the best protections in winter
for herbaceous perennials. Less snow may lead to more plant
losses, and actually the ability to grow fewer perennials than now
in areas with sufficient and reliable winter snow cover. Overall
snow cover in the Northern hemisphere, particularly the far north,
has declined each year since 1986 except one, with a steep decline
since 2003 (Rutgers University snow lab).
Consequences of too much water include springtime flooding
delaying planting; root damage and reduced yields; soil loss from
erosion and silt deposits when land floods; and contamination of
water from runoff. So, what can gardeners do, in addition to
getting a good pair of boots, to prepare their gardens and
landscapes for more water? These tips are particularly relevant
if you have soils or areas that tend to stay wet and soggy after
downpours, or that may even flood periodically.
Choose tolerant plants for wet 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
Use raised beds to grow above the wet soil; the longer the soil
stays wet, the higher the bed should be (one foot or more). Grow
shrubs or trees on slight mounds.
Avoid working on soils while wet, as this will destroy soil
structure. What’s too wet? A ball of soil in your hand should
hold together, but crumble when pressed and not ooze water.
It’s hard to add too much organic matter, such as compost, to
soils, particularly if they’re sandy or gravelly. In addition to
helping the soil dry out more quickly, organic matter improves
soil physical properties and helps feed beneficial soil microbes.
Minimizing, or even avoiding, soil tillage (using a spading or
broad fork to loosen soil is better) preserves soil structure
which, in turn, helps it to recover more quickly after heavy rain.
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 water.
Reduce stormwater runoff from paved surfaces by using permeable
pavers and surfaces. These work on surfaces that don’t slope more
than one foot over a horizontal distance of 20 feet. While you
might create such walks and patios yourself, a professional
landscaper is best for large surfaces such as driveways made of
permeable pavers. If you have steps up a slope, or need to make
some, consider permeable ones for infiltration.
Create rain gardens as a destination to hold water from heavy
rain events, allowing it to percolate back into the soil over time
(www.groundwater.org/action/home/raingardens.html), or vegetated
swales to treat water flowing through an area. Even simpler than
a swale is a diversion ditch or channel, filled with gravel or
pebbles. These are what often are placed under the dripline of
roofs. Use attractive large pebbles or river stones to create an
attractive creek bed feature in your landscape.
Another runoff option might be to simply dig a small pond where
water can flow during a heavy rain, even if the pond doesn’t have
water all year. Such catchment ponds sometimes are seen near
parking lots to catch runoff.
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 crops, as it may contain pollutants.
Consider installing green roofs on sheds or garages to slow and
Avoid removing too much vegetation from slopes, to avoid erosion
during heavy rains. If you have a fresh slope, add vegetation
such as grasses or cover crops. If you want or need to plant
them, consider terracing using wood, stones or hardscape materials
if the slope is steep.
There’s not much you can do if an area is flooded except to be
patient, and hope that the water subsides soon. 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. If any plant parts were underwater, wash them off
with the hose.
Watch for signs of diseases; also watch for nutrient deficiency,
fertilizing as appropriate or using foliar feeding (spray
fertilizer onto leaves). For edible plants, destroy greens,
produce eaten raw, and any other vegetables near to harvest. Wait
until next season to grow crops, that are to be cooked, on that
site. Wait two seasons to grow salad crops or those to be eaten
raw, so potential diseases can leave the soil.
Don’t forget your container plants during heavy rains. Having an
organic, well-drained potting mix goes a long way to helping
containers dry out quickly. Of course, with advance notice of
incoming rain and if containers are easily moved, consider putting
them under shelter.
If containers are in an area that floods and they’re under water,
or sitting in it a while, carefully remove the plant from the pot
and let the roots dry out in an area out of direct sunlight, and
with good air movement. Wash the pots well and, if plants are
still relatively small, repot them into some fresh and dryer
potting mix. If you have vegetables in containers that were
flooded, use the same precautions as those grown in field soil.
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