Gardening for climate change
Those who track and study the weather say the average daily temperature on this planet has risen one degree over the last century. Doesn't seem like much, but remember, the twenty hottest recorded years all occurred in the last quarter century. If projections that the average daily temperature will rise from 2.5 to 10.5 degrees over this coming century are correct, how will that affect the Southern Oregon gardener?
"What we have seen is that the U. S. Department of Agriculture hardiness zones are moving north," says Bob Reynolds, Southern Oregon Research and Extension Center urban horticulture instructor. "Anecdotally, we hear that gardeners can grow things now that were iffy 15 years ago. But we are also getting more extreme weather and more intense storms."
Although the U.S. Department of Agriculture is working on a new hardiness zone map, there has been a delay in its release. In the meantime, the National Arbor Day Foundation has come out with a revised map. According to its map, most of us have moved from Zone 7 to Zone 8.
Spring has shifted forward an average of six days in North America since 1959. So what is the problem with plants flowering earlier? Some plants are blooming even earlier, leaving them subject to late winter frost kills. Iris plants in the Northeast have bloomed earlier every year for the last 30 years. Another problem is migratory birds and insects, who may not arrive in time to fulfill their part of the delicate ecological dance of pollination and protection. And weeds seem to adjust to more heat and less water faster than the plants we want in our gardens.
It's a good news/bad news situation for our valleys. As California gets hotter, Southern Oregon could replace Napa and Sonoma as the ideal grape growing area, but the varieties of grapes we could grow would shift, also. We already have a Mediterranean climate, but milder winters and increased summer heat means we will fall more into that range. They harvested pomegranates at the research center this year, and some people are trying hardy varieties of olive trees.
While Jacksonville pioneer Peter Britt was able to grow bananas and palms by wrapping the trees in winter and moving them into a greenhouse, we may find these are just some of the semitropical and tropical plants that will fit into our new climate. But native plants that we are used to seeing here may soon find they lack summer water and enough cold days during winter necessary to flourish.
Global warming means less snow and more rain. What is wrong with that? Snow pack is our water bank — we rely on the gradual snow melt to provide water over longer periods. More winter rain will mean different plants will survive our winters: some will wash out, others will drown or rot. Gardens with plants from Mediterranean-type gardens will thrive. Another strategy is to plant on berms, so roots can escape waterlogged clay. We may have summer droughts which is sure to increase chances for wildfire.
Therefore the future of gardening in the Rogue Valley will require efficient watering systems. Fire resistant landscaping with succulents will likely become very important. And forest clean-up practices will be key.
"It's going to be more important to build soil heath," says Dan Bish, owner of Plant Oregon in Talent. "Using compost and cover crops will be essential. Healthy soil means plants will be more drought-resistant."
Practices like intensive vegetable gardening will become more expensive, so you may want to start a sustainable vegetable garden. "The price of food and supplements like nitrogen are going up with gas prices," says Bish. "People are going to need to learn to plant more nitrogen fixing legumes like clover or peas."
Giving plants more root room instead of more fertilizer will provide good yields in the vegetable garden. Learning how to handle a compost pile or worm bin are planet healthy practices — you'll be cutting greenhouse gas emissions and giving your garden the nutrients and organic matter it needs to stay healthy, whatever weather the climate changes may send our way.