Spring is on the way, and from a plant's point of view, it's coming at light speed.
Lilacs, forsythia and red maples are blooming, on average, about two weeks earlier in the Chicago area than they did in records from the 1960s and 1970s, according to data collected by scientists and gardeners for Project BudBurst (budburst.org).
In Ohio wetlands, 39 percent of native species are blooming earlier than they did just a decade before, according to a 2010 University of Cincinnati study.
To scientists such as Kay Havens, director of plant science and conservation at the Chicago Botanic Garden in Glencoe and lead botanist for 4-year-old Project BudBurst, these and similar data collected across the country clearly show how the changing climate is affecting plants.
A longer growing season is one prediction for the Midwest in the U.S. Global Climate Change Research Program's 2009 assessment. In coming years and decades, rain and snow will come in heavier storms, with longer dry spells in between. There will be more floods, droughts and heat waves. On average, winter nights won't get as cold, so weeds and insects will have a better chance at surviving until spring.
What does all this mean for a gardener?
Day to day and year to year, the weather will be as variable as ever. We've had one of the warmest and least-snowy winters on record, coming right after one of the snowiest — and that kind of year-to-year swinging won't stop.
Research is just beginning into which plants have the best chance to survive and thrive in these changing conditions, Havens says. But it makes sense to factor climate change into gardening and long-term plans.
Some standard principles of good gardening will be as important as ever: Composting and adding organic matter to improve soil and nourish plants, and maintaining a layer of mulch — which will become more important as that insulating layer of winter snow becomes more rare.
Here are some ways a gardener can adapt, and perhaps even help:
Plant shade trees: In heat waves to come, shade will be a boon. Large trees also can help handle water from those heavy rainstorms, trapping it in their leaves and trunks where it can slowly evaporate, Havens says.
Tough, tolerant native species can support our homegrown birds and insects, which may have a tougher time finding food and dwelling places. Look for species with a wide historic range extending south and west of Chicago. For example, Havens says, paper birch, native to northern forests, has little chance of surviving in this area in years to come. A better bet would be a river birch (Betula nigra), which is more tolerant of the conditions we'll be likely to see. For a large shade tree, consider a swamp white oak (Quercus bicolor). Other good options: American linden (Tilia americana) and Kentucky coffee tree (Gymnocladus dioica).
Plant resilient natives: Midwestern prairie natives, which evolved to cope with a range of weather, are likely to adapt well, Havens says. Some choices: prairie coreopsis (Coreopsis palmata); prairie dropseed (Sporobolus heterolepis); spiderwort (Tradescantia ohiensis).
Choose plants wisely: "The right plant for the right place" will be as good advice as ever, if you're alert to your places' current conditions, not the ones you may be used to. If they are perennial, Havens says, "they need to be tough plants that are going to experience greater extremes of both wet and dry."
Pick plants that resist pests: Insects and diseases likely will become more prevalent. Better to pick species and cultivars that are naturally resistant, or tolerate a certain level of infestation, than battle bugs with chemicals.
Brace yourself for weeds: Plants that once couldn't survive a Chicago winter will thrive. We'll likely begin seeing new weeds such as kudzu and more poison ivy. Invasive species will become a greater problem.
So don't plant potential invasives: With a longer growing season and warmer winters, more species of plants may escape from our gardens and overtake natural areas. "Things that have a tendency to be weedy will be even weedier in the future," Havens says.
Welcome pollinators: It may be harder for some plants to get the pollen they need to form fruit if the insects they depend on no longer hatch at the right time. To bolster the population of pollinators, plant nectar-bearing plants.
Allow for stormwater: Bigger storms mean your landscape will need to handle larger volumes of rainwater than ever before. Try to keep water on your site using rain gardens or swales that slow water down and soak up much of it before it overwhelms sewers. A rain barrel is a good first step toward managing stormwater.
Prepare for drought: Between big storms there likely will be more and longer dry spells, and water may become more expensive or scarce. So look for plants that tolerate drought. Aim to gradually build a garden that mostly doesn't need irrigation, and group the needy plants, such as vegetables and annuals, where it's easy to water them.
Helpful resources
"The Climate-Friendly Gardener" from the Union of Concerned Scientists: ucsusa.org
"Climate-Friendly Gardens and Lawns," Chicago Wilderness Climate Action Plan for Nature, Community Action Strategies from the Field Museum: climatechicago.fieldmuseum.org
Landscape for Life website from the Lady Bird Johnson Wildflower Center and the U.S. Botanic Garden: landscapeforlife.org
The Chicago Botanic Garden maintains useful listings of both native and invasive plants: chicagobotanic.org (click on your garden link).