The Dirt: Weatherscaping
Climatologists, as well as the National Oceanic and Atmospheric Administration (NOAA), predict increasingly intense and frequent extremes of heat, precipitation, and other weather events in coming decades. Surely we have seen record-breaking storms, heat waves, and floods in 2011 alone. Whatever we believe about climate change, weather trends, and their causes, wouldn’t it be smart to get proactive and prepare our landscapes for nearly anything? Let’s call it weatherscaping for the extremes.
One sentence should effectively cover ninety-five per cent of landscape preparedness: good horticulture determines whether plants will survive most conditions. This premise summarizes four years at hort college: If you choose plants that suit your soil and site, and if you care for them properly, your plants will live unless something unusual happens. So let’s get ready for the unusual.
Winds do the most landscape damage when they concur with freezing rain or heavy snow at a time when trees still have leaves, e.g., the October Surprise of 2006 and the famous 1991 Rochester ice storm. To minimize the damage:
• Choose trees with strong branch structure, e.g. wide branch angles, not tight V-shaped crotches.
• Avoid weak-wooded trees that break easily, e.g., silver maples or Chinese elms.
• Hire an arborist to inspect and groom large, older trees, remove hazardous branches, and open up canopies to allow wind passage.
• Plant large trees far from the house, so limbs will never hang over the roof.
• Avoid planting early-flowering trees in high wind areas; it’s disappointing when high spring winds blow the flowers off.
• Keep outdoor lighting away from tree canopies. Many trees drop their leaves in response to decreasing daylight; outdoor lighting inhibits the process, and the leaves stay on.
• Don’t fertilize or prune extensively in late summer and early fall, as it can encourage lush, weak growth that increases the risk of blow-over.
• During construction or other disturbances, protect tree roots—the tree’s anchors—well beyond the tree canopy. Protect trunks from wounding also.
• Maintain good drainage. Dig ditches where needed; shallow-rooted trees in wet soil tip easily.
• Don’t change the soil grade around a tree. More than three inches can drastically weaken it.
• Create a windbreak—sturdy shrubs, walls, or fences—to block high winds that can damage plants or blow away dry soil or mulch.
• Water the garden—including soil and mulches—before a windstorm.
• Where appropriate, plant cover crops such as buckwheat, clover, or oats to hold soil in place and retain soil moisture
• Choose shorter plants (bush instead of pole beans) and instead of staking tomatoes, let them sprawl.
• Choose in-ground water methods over sprinkling systems, or hand-water using nozzles aimed at plant bases to avoid water loss to the wind.
Floods and droughts
One might think these are separate risks that should be addressed differently. Surprisingly, in anticipation of too much or too little water, we should make similar design and layout changes in the landscape, and even use many of the same plants.
Xeriscape for plant survival
As the root “xeri,” meaning dry, indicates, xeriscaping refers to dry-period gardening, but these sensible practices would increase plant survival in both wet and dry times.
• Group plants by water requirement. Prairie grasses and succulents go to high ground or raised beds with great drainage, and cluster bog-preferring plants (see Rain Garden sidebar).
• Grow less or no lawn; lawn is a water guzzler. Replace it with low-maintenance groundcover, perennials, paths, mulched areas, and permeable paved surfaces.
• If you have a lawn, keep it tall—over three inches—to preserve soil moisture, and let it go dormant in summer.
• Plan in-ground watering systems to serve only selected plants (e.g., important trees) in time of need. Hand water at the base of plants when necessary.
• Add compost to both lawn and garden soil; compost helps retain soil moisture.
• Make the most of the water you have: reuse household (gray) water, water in the morning for best efficiency, and place rain barrels to capture rainfall or roof runoff.
In flood areas
• Choose trees and shrubs that tolerate standing water.
• Keep a thick, healthy lawn, and create dense plantings that filter runoff.
Extreme heat and cold
Veteran Western New Yorkers know lots about severe winter temperatures. We also tend to understand what plants to cover and how to get them through winter—for example, although we have been rezoned as a United States Department of Agriculture Hardiness Zone 6a, smart gardeners will continue to place “Zone 6 plants” in protected locations.
We are generally not as well versed in hot weather gardening, since our region typically enjoys moderate summers. But what if the heat waves get longer and hotter? The American Horticultural Society has a Heat Zone Map showing anticipated heat extremes by region, with thousands of plants categorized for their tolerances. This list might show us, for instance, that Bacopa and Nemesia won’t take the summer heat, but Portulaca and Mandevillas will be winners. Still, there are so many other factors—plant provenance and age, soil, light, breeze, watering practices—that we have more to learn than charts can tell us. When a plant dies, we may never be sure which combination of factors provided the final stressors.
Meanwhile, in the hottest of summers, we can mulch, water, and provide some shade, even for sun-loving plants. Perhaps someday, we’ll know as much about hot summer gardening as we do about keeping plants alive over winter. I’m hoping we don’t need that expertise too soon.
Weather will always be the least controllable and most influential factor in determining our plants’ survival. Droughts, heat, flooding, windstorms, and freezes—surely some, if not all, will be part of our stories in the decades ahead. Weatherscaping is our best defense.
Sally Cunningham is an author (Rodale Books) and lecturer, Certified Nursery & Landscape Professional, and garden/landscape consultant at Lockwood’s Greenhouses in Hamburg. She is also director of the National Garden Festival (nationalgardenfestival.com). She does believe in being prepared.