Installing a living windbreak can lead to big improvements in garden yields and harvest quantities. Plus, research briefs on tree-killing mosses, praying mantises, ionized air and plant growth, increasing grapevine productivity by mulching with silver film, and millennium-old worn-out soil.
Shelter from the wind can lead to big improvements in garden yields and quality. And not just for row crops in the Great Plains—your own backyard plot can benefit from properly designed windbreaks. Some crops that produce better when out of the breeze include strawberries (earlier ripening and higher yields), raspberries (higher yields due to production of more canes), watermelons (improved fruit quality because of less wind whipping, sand abrasion and leaf drying), tomatoes (increased early yield due—apparently—to higher temperatures), potatoes (earlier maturing), snap beans and okra.
For a backyard garden, the most important effect of a good windbreak is an enhanced microclimate, with increased humidity and temperature. Here are some design guidelines from experts at the first International Symposium on Windbreak Technology:
1. Living windbreaks (trees, shrubs or both) are inexpensive to plant and maintain but don't give full protection for at least a few years. Constructed windbreaks offer "instant" protection—but at a higher price.
2. Orient windbreaks at right angles to the prevailing wind direction(s) or as close to that as possible. Plantings along west and north property lines are common (but beware of blocking cool summer breezes). Avoid plantings on the south side—you don't want to shade the garden. A windbreak should be at least as long as the garden it's protecting. And don't put a windbreak on the top of a ridge; it may increase leeward turbulence. Put it a little downhill on the windward slope.
3. Protection distance is proportional to windbreak height. Typically, crop yields and quality are most improved at distances between three and six times the barrier's height. However, crops close to a living windbreak (less than its height away) are likely to have reduced yields, due to competition for water, nutrients and light.
4. Moderately dense (50% to 80%) windbreaks work best. (Low-density ones don't slow the wind enough; high-density ones create excess leeward turbulence.) Single-row living windbreaks are adequate but are susceptible to gapping when individual plants die. Consult your local Soil Conservation Service for specific species suggestions (columnar-form trees generally work well). Recommended spacings range from five to eight feet for shrubs and small trees and from six to 21 feet for larger trees, with the narrower spacings more appropriate for single-row plantings and the wider spacings for multi-row barriers.
A scientist with the National Center for Atmospheric Research has discovered that mosses can kill trees by generating organic acids that make toxic soil aluminum more available to the trees' roots. Acid rain appears to aid growth of the tree-killing mosses.
Are praying mantises really "good guys"? Probably not, according to some biocontrol experts. After all, while mantises devour many pest insects, they're just as happy to chow down on beneficial ones. Another drawback to importing their egg cases is you won't get many of what you worked (or paid) for: The little prayers have a high mortality rate.
Those desktop air ionizers may or may not promote human health—but they definitely help some plants. Romanian researchers report that tomato seedlings exposed to ionized air grow taller and have larger stems and more leaves than un-ioned ones.
Korean scientists report that grapevines mulched with silver reflective film grow faster and produce more highly colored grapes (with higher concentrations of soluble solids) that ripen earlier than unmulched vines.
Agronomists recently examined a New Mexico site that was cultivated by Native Americans between A.D. 1000 and 1050, then abandoned. After almost 1,000 years the cultivated soil was still compacted, low in organic matter and plant nutrients (especially nitrogen), and highly erodible. So it really is true: You can wear out soil for a millennium. Please be good to your great-great-great-grandchildren's soil. Greg and Pat Williams raise most of their food on a small farm and publish HortIdeas, a fine newsletter on gardening research and products.
Greg and Pat Williams raise most of their food on a small farm and publish HortIdeas, a fine newsletter on gardening research and products.