Global Warming in the Garden

This overview of current thinking on the subject was published in my local paper and prompted a nice thumb’s up from Mike Tidwell, a well known enviro leader locally and even nationally – whew!- so I’m passing it on for readers here.

There’s been lots of
news lately about the effects of climate change on our gardens and
oddly, it’s usually presented as good news to gardeners. They’re shown
rejoicing over the warm-climate plants they can now grow, like crape
myrtles in Upstate New York. BUT:

It’s Global Weirding 

• Some plants are failing
  because the winter cooling period isn’t long enough. And others, like
  lilac, Eastern white pine, American arborvitae, Colorado blue spruce,
  and many junipers, suffer when summer evenings don’t cool down enough.
  Local garden writers are no longer recommending many of their old
  favorites for local gardens – like PJM rhododendrons and yews. 

• Rain events are more extreme, taking the form of longer droughts and
  more deluges. Not good for landscapes, for agriculture or for plants in
  our few remaining natural areas. 

• Longer warm periods mean more generations of some pests per year.
  Others, like the wooly adelgid that’s killing Canadian hemlocks
  throughout the East, are increasing their number because winters aren’t
  cold enough to keep them in check. 

• Weedy and noxious plants, like poison ivy, honeysuckle and kudzu,
  thrive in the presence of extra carbon dioxide, and poison ivy becomes
  more toxic than ever. Ragweed produces more pollen. Kudzu moves north.
  Some weeds, like Canadian thistle, are now resistant to herbicides.   

• Native plant populations are threatened by these changes in
  temperature, rainfall, pests and competitors, even the iconic ones
  chosen as state flowers and trees. In fact, the National Wildlife
  Federation predicts that 28 states will see their official plants
  become extinct by the end of the century. Picture Ohio without its
  buckeye or Kansas without its sunflower. Climate change has become a
  major threat to plant conservation, along with development and invasive
  species.
   

• The East experienced a
  Miami-style January this year, followed by a frigid February. These
  alternating balmy+frigid periods take their toll on blossoms and whole
  plants. Fruit growers were particularly hard hit. 

• Hotter summers cause heat stress even to warm-season crops, like tomatoes, according to Cornell University. 

More to Come? 

The
life cycles of insects, including the beneficial ones that keep others
in check, may become out of synch with their prey. Pollinators, like
the disappearing honeybees, may already be out of synch with the plants
they feed on. Science Magazine reported in 2001 that earlier flowering
and fruiting has caused such a disconnect for some long-distance
migrating birds, who depend on food availability at the same time each
year. And to make everything worse, most climate modelers predict more
flooding and drought. 

Even English Gardens are Adapting 

To
see how gardeners might adapt to all this change, let’s look first at
what’s happening in England, a nation of gardeners. Last summer their
southeast region had such a severe drought that sprinklers were banned.
With more and longer droughts predicted, it’s clear that the very
hallmarks of English gardening are now threatened – their traditional
lawns and flower borders. 
 

Thus the U.K. Environmental
Minister is urging everyone to change their water usage, plant choice
(look for drought- and heat-tolerance), and garden design – in other
words, change everything they’re doing. No more roses and delphiniums.
The use of gas-powered garden equipment is discouraged. Rain barrels
are recommended, as are carbon-sequestering cover crops, like clover
and winter rye. Brits are being given at least one bit of advise that
fits their culture: plant roots are darn good at absorbing carbon
dioxide, so plant more of them.

Changing Our Gardening Practices 

Here
in the U.S. we see the mainstream gardening media beginning to respond,
with both Martha Stewart and Better Homes and Gardens advocating less
gas mower and blower usage. Gardening authorities across the U.S. are
offering these very good suggestions: add organic matter to make your
soil hold moisture better, plant shade trees on the south side of your
home to reduce air conditioning loads, and do your planting in fall or
early spring. Even turfgrasses can be damaged by the freeze-and-thaw
events we’re experiencing, especially where there’s standing water, so
we’re being told to fix our drainage problems. 

Choosing Different Plants 

Research
has really just begun, but here are the kinds of plants being
recommended by gardening experts in response to global climate change:

Perennials
from Mediterranean climates, which thrive without summer rain. Examples
are such beautiful and useful plants as lavender, rosemary, sage,
catmint, oregano, and thyme. The herb agastache flowers nonstop through
the summer and is beloved by bees, and red agastache is a magnet for
hummingbirds. Locally native plants are particularly good for
sustaining wildlife, but be sure to ask for ones that will survive the
new climatic conditions.
 

Choose trees and shrubs that do well
across many temperature zones. Some have seeds that can shift
strategies quickly, rather than the generations it usually takes for
most trees to adapt to new conditions, which makes them so vulnerable
to climate change. Oakleaf hydrangea, serviceberries, deciduous
magnolias and many pines are especially adaptable to a range of
conditions. Again, the science is evolving, with experts at Cornell
currently saying they haven’t yet seen changes that cause long-term
damage to trees and shrubs. 

How Gardeners Can Help Reduce Climate Change

To
borrow from one of the central tenets of organic gardening, the first
goal of gardening should be to do not harm. Here are some ways:
 

• Stop using gas-powered lawn equipment or products that use fossil fuels
  in their production, like synthetic fertilizers. Gas mowers spew as
  much pollution in one hour as a new car does in 40 hours – that’s how
  terrible the gas-mower technology is. And those synthetic fertilizers
  can be replaced primarily by compost and organic mulches, supplemented
  with organic, slow-release fertilizers when an extra boost is needed. 

• Instead of blowing leaves into plastic bags for them to be trucked away
  to landfills or to an incinerator, turn them into soil, by composting.
  Home compost operations help lighten pressure on landfills and result
  in more water-retentive soil for the gardener – that really cool circle
  of life thing. Some municipalities collect leaves and turn them into
  free leafmold mulch or compost. 

• Grow
  your own food. It’s fresh, it’s as organic as you want it to be, and it
  doesn’t have to be trucked or flown in from far away. In the
  alternative, frequent our local farmer’s markets. 

• Finally, the quaint suggestion that we bring back a garden ornament
  from our grandmothers’ gardens – the clothes line – comes from the
  Goracle himself.    

More On-line Info about Climate Change in the Garden
 

• My article Carbon Calculations in the Garden, orginally published on GardenRant.com.
• Both Cornell and the Brooklyn Botanical Garden are excellent sources.
• This is a good overview of global warming, carbon credits and the positive contribution made by organic gardening. 

General Sources About Climate Change    

• Chesapeake Climate Action Network
• Real Climate.org
• Weather and Climate Basics
• Wikipedia

Article originally published  in Maryland’s Voice Newspapers.