Tips for weed control

August 28, 2017 | Posted in: Uncategorized

1. Crowd out weeds with thick lawn cover

The best defense is often a good offense. This means keeping the lawn thick and healthy to keep weeds from having any room to grow. You can also add groundcover plants and other thick plantings to crowd out weeds in decorative beds

“Weeds are simply plants that take advantage of open areas with available resources,” said Robert Hartzler, an extension weed specialist and
professor of agronomy at Iowa State University. “The simplest way to control weeds is to eliminate the open niches that they take advantage of.”

Richard Zollinger of the North Dakota State University Department of Plant Science offers a simple two-prong strategy. “To minimize weed problems in my lawn as a home owner, I mow my lawn high and optimally fertilize to keep the lawn as competitive as possible,” he said.

Smith recommends reseeding lawns in the fall to prevent weed growth. Since many weeds are already dead late in the season, there is less competition for space as grass seeds try to take root. Smith also recommends strong, high-quality grass seed. Look for the highest germination and purity percentages available.

2. Maintain healthy soil

Once you have put in desirable plants that crowd out weeds, keep your plants healthy with fertile, aerated and well-drained soil. Test your soil and talk to local specialists to create the optimal fertilization plan. Unfortunately, weeds can grow in virtually any soil, but soil improvements will at least create a level playing field with your plants.

“Most weeds don’t have specific requirements for growth other than open areas. It usually isn’t possible to eliminate weeds simply by supplying some specific nutrient,” Hartzler said. “However, anything that can be done to promote the growth of the desirable plant will reduce weed problems. Weeds often benefit as much, if not more, from the application of fertilizer, so blindly applying nutrients in the hope of suppressing weeds can be counterproductive.”

Soil compaction is a concern under lawns, but can be overcome with core aeration every three or four years, said Smith.
. Till the garden

Loosening and turning over the soil is useful for managing weed populations, but tilling should be performed with caution. Tilling may simply rotate weed seeds. Hartzler explains the advantages of tilling.

“It provides a clean start for the crop and simplifies weeding. It can bury a lot of seeds at depths where they are unable to successfully establish. This can be a real benefit if a lot of seeds were produced the previous year and are laying on the surface,” he said.

However, dormant weed seeds may be brought back to life with tilling.

“Seeds buried more than three to four inches deep are much more persistent since there is a lot less biological activity at this depth. The next time the garden is tilled, some of them will be brought to the surface where they can germinate,” Hartzler said.

4. Hoe the topsoil

Carefully hoeing the topsoil can effectively control some weeds but, like tilling, hoeing has its limits.

“Hoeing can be very effective for controlling annual weeds. However, perennials often resprout from the roots after the tops are removed,” said B. Rosie Lerner, an extension consumer horticulture specialist at Purdue University.

Lerner said only the surface needs to be hoed to pull away young, small weeds. “Hoeing should consist of short, shallow strokes that simply cut off the weeds at soil level,” she said. “Hoeing deeper will only bring more weed seeds to the germination zone and may injure the roots of desirable plants growing nearby. … Weeds will be much easier to pull or hoe while they are still small.”

5. Mulch garden beds

Tom Lanini, a professor of plant sciences at the University of California Davis, said mulch is the most important factor in preventing weed growth. Nearly any barrier that blocks light works as a mulch. Bark and other decorative mulches work, but dried leaves, cardboard and newspapers are also effective.

“I think organic mulches are definitely the way to go. They have benefits beyond weed control.” Hartzler said.

Lerner notes that organic mulches improve soil structure, and add nutrients, particularly when used near the end of the growing season. They also keep the soil cool and reduce water loss to evaporation.

Straw and hay are among the cheapest mulches, but they must be free of weed seeds to be effective. Like other methods, mulch may be less effective on established perennial weeds. They are better at blocking smaller annual weeds.

6. Cover the ground with landscape fabric

Landscape fabrics are thin barriers covered with tiny holes. They are typically made of plastic, but may also be sheets of burlap or other natural fibers, or recycled plastics. They are effective at blocking weed growth while allowing water and air into the soil. They should be used in conjunction with thick, effective mulch.

“As a garden mulch, fabrics do provide good early-season weed protection. However, because fabrics allow some light to penetrate, weeds will germinate below and break through the cover unless some other material, such as rocks or bark mulch, are placed on top,” Lerner said.

According to Dr. Andrew Senesac of the Long Island Research Laboratory, landscape fabric will block many weeds, but it also limits some desirable flower production by restricting the spread of shoots, and inhibits the spread of some groundcovers and other spreading plants.

Some particularly hardy weeds and grasses can even germinate with no soil on top of porous weed barriers, then force their roots down.

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