Be Prepared to do Battle Against Weeds

Filed in Gardening by on April 19, 2014

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Gertrude Stein is famous for saying, “A rose is a rose is a rose.” I say, “A weed is a weed is a weed.” (Who the heck is Gertrude Stein anyway?)



In truth, what constitutes as a weed is mostly in the eye of the beholder. In my lawn, for example, a dandelion is a weed. But I have friends who think fields of dandelions are beautiful, and in Europe dandelions have been cultivated for hundreds of years and their various parts used in making teas, wines and salads. Perhaps the best definition of a weed, then, is a plant out of place, a plant growing where you don’t want it to grow.

Of course, some weeds are weeds, and we are prohibited from growing them in Minnesota (should you want to). They are difficult to control or injurious to the public health, the environment, roads, crops, livestock or property. Included on the noxious weed list are various thistles, field bindweed, leafy spurge, purple loosestrife, poison ivy, garlic mustard and hemp.



If you’re lucky, you don’t have any noxious weeds growing in your yard, but you probably have a few plants that are “out of place.” Some may simply be vigorous growers like mint or monarda, which need to be kept in bounds. Others, like purslane, lambsquarters, chickweed, pigweed, crabgrass and quackgrass, are weeds by most people’s standards. These compete with desirable plants for sunlight, nutrients and space. They can also harbor insects and disease. For the health and beauty of your landscape, prepare to do battle with the likes of these.

But it can be hard to combat weeds. One lambsquarter plant, for example, can produce 75,000 seeds, and those seeds are viable for many years. Ragweed seeds can survive in the soil up to 80 years. The rhizomes of one Canadian thistle can grow as deep as three feet and more than 15 feet laterally. A little neglect, a little wind, a little passage of time, and one or two weed plants become thousands.

So how do you combat weeds? In gardening, as with most things, an ounce of prevention is worth a pound of cure. Ensuring that new beds are free of weeds before planting is a good beginning. Close spacing of perennials helps eliminate weed competition. Removing weeds before they go to seed will save weeks if not years of future attempts at control.

A layer of mulch is a good way to suppress weeds; it prevents weed seeding from germinating by block out light. Mulch can also help soil retain moisture, buffer soil temperatures, reduce the spread of soil-borne diseases and prevent soil erosion during heavy rain or strong winds.

Different plants require somewhat different mulching practices. Trees and shrubs benefit from a layer of coarse wood chips or bark. The coarser the texture, the deeper the mulch that can be applied – up to about 6 inches. Anything deeper than that will begin to block the flow of oxygen in and out of the soil. Maintain a mulch-free zone immediately around the trunk or stem bases, as piling mulch up around the base of plants encourages fungal decay and rot. Rock is popular for mulching around trees and shrubs, but it may absorb enough sunlight to alter soil temperature unfavorably.

A light fine-texture material is most suitable for perennials. Pine bark, for example, is easy to apply and to work with later for any additional planting. Apply two or three inches of mulch in perennial beds – deep enough to keep soil from splashing onto the undersides of the plants, which will reduce the spread of soil-borne diseases, but not so deep as to smother plants. Keep the mulch away from the crowns of perennials, as mulching over the crown will cause rot.

Annual flower beds and vegetable gardens do best with organic mulches that will break down rapidly when tiled into the soil at the end of the season. Shredded leaves, partially decomposed compost, or cocoa bean hulls are all good choices. If annuals are directly seeded into the bed, wait until they are several inches high and you have weeded at least once before applying 1 to 2 inches of mulch. Vegetable gardens often produce larger and healthier crops when mulched at the correct time. Wait until soil has warmed thoroughly for heat-loving crops. Mulch cool season crops early in spring.

Even the best weed prevention methods will not keep weeds out of your yard entirely, though. When these pesky plants make an appearance, remove them quickly to keep them from spreading. Good luck.

by Reba Gilliand, a Master Gardner in West Otter Tail County. 

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