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seeds to kill weeds

Of course, if you use an organic mulch (such as a bark mulch), it will eventually decompose anyhow, becoming fertile ground for weeds. What can you do? Well, you had better keep new weeds pulled, faithfully. Vigorous roots pushing downwards can stress landscape fabric and breakthrough. On the bright side, these weeds should be relatively easy to pull, since mulch is a lot looser than dirt, and weed roots will not become impossibly entrenched.

Cover the raked, moistened area with a clear polyethylene sheet. The edges of the sheet can be held down by cinder blocks to keep the plastic from blowing away. If the raking mentioned above was done diligently enough, there will be no sharp objects sticking up to puncture the plastic. The sheet of clear plastic can be anything from 1 to 6 mil. in thickness. In the Northern hemisphere, the best time for soil solarization is June and July, when the sun is at its peak. UIE recommends keeping the sheet of clear plastic tightly stretched out over the area for about 2 months. During that time, the sun will be killing weeds for you—”cooking” them before they have a chance to sprout. Plant pathogens will be killed, to boot.

If there are shrubs and trees present, cut them down with an ax or chainsaw. The ground needs to be smooth before you begin soil solarization (since you will be spreading plastic over it), so you will also have to remove the stumps left behind. If you are looking for a cheap way, use a tool called a “mattock.” Dig and chop your way with the mattock under the root-ball to access and remove the taproot. Warning: this is hard work and may be feasible only for smaller stumps.

Preparation

Now use a steel rake on the area that you have just tilled, wielding it like a fine-toothed comb to remove the majority of the uprooted weeds. Next, rake the area again, this time with the object of evening out the soil as best you can and removing stones, twigs, etc. The final preparation for soil solarization will require the use of a garden hose. According to the University of Idaho Extension (UIE), you should moisten the area that you have just raked to “conduct and hold heat, to stimulate weed seed germination, and to prevent dormancy of below-ground vegetative plant parts.”

First hack down the tall vegetation with a sickle, power trimmer, etc. But before doing so, make sure you know how to identify poison ivy, poison sumac, etc.

Now you truly have a “clean slate” with which to work. Remove the plastic and lay down landscape fabric. You should try to use one of the stronger types of landscape fabric if possible, just in case—in spite of your best efforts—any sharp objects remain in the ground (which would puncture the landscape fabric).

Soil solarization is a preventive, organic method of killing weeds before weed seeds even sprout.   But the advice below is also meant for homeowners wishing to start a garden with a clean slate, reclaiming a patch of land where weeds have taken over, in such a way as to reduce to a minimum the hassle of future ​weed control. Want to transform a piece of land that has “gone to pot” into usable space? Then the method explained below may be the solution to your problems.

Cover crops can be a tool for weed seedbank management. “Cover crops have had a long history in the Midwest, and can make a comeback should market forces and weed management realities combine to make them necessary,” Davis says. “Adding cover crops to the weed management toolkit can reduce opportunities for weed seedlings to establish, and can also provide a critical delay in weed seedling emergence so that crop competition can further suppress weeds.”

As a graduate student, Adam Davis spent his Septembers crawling around on his hands and knees through crop fields trying to find and recover giant foxtail seeds for his research studies. He soon discovered that seed predators had already eaten the seeds on the soil surface. Mice, crickets, ground beetles and other organisms were doing a highly effective job at reducing the number of weed seeds.

“I began to measure weed seed predation and saw that within two days, nearly all of the seeds I’d put out in the field [to measure the amount of weed seed predation] would be gone,” says Davis, an ecologist with USDA’s Agricultural Research Service at the University of Illinois. “Over the course of a growing season, I’ve seen weed seed predators eat between 40% and 90% of the seeds produced that year. It’s an important weed management benefit that we take for granted, but which really makes a difference.”

Weed management toolbox

Davis conducted that early research to evaluate a valuable option for growers who want to manage hard-to-control weed populations: Manage the weed seedbank to prevent weeds from getting started.

The key to weed seedbank management is to reduce the ability of the seeds to germinate. Then growers either don’t have the weeds to control or they have fewer weeds to handle with other weed management tools. Here are Davis’s suggestions for managing a seedbank:

“We focus on killing weed seedlings because we can see them, and we have products available to do this,” Davis says. “Certainly, we don’t want to give up managing weed seedlings, but if we reduce weed seedbank population densities, managing weed seedlings becomes much easier.”

Davis says the most important element of a successful weed seedbank management strategy is to implement a diversified crop rotation so crops with contrasting life histories are grown in different phases of the rotation. “This prevents any one weed species from getting too comfortable, and makes it difficult for weeds to reproduce in the canopy of a crop with a different life history,” he says.

Non-Selective Herbicide: Kills any green and growing plant, whether or not it’s a weed.

If you have a yard, you have weeds. They may lurk in the lawn, thrive under a shrub or flourish in flowerbeds, making weed control a constant battle. It requires patience, persistence and knowledge – of both types of weeds and the weapons you have to eradicate them.

Examples: Chickweed, Crabgrass, Lamb’s-Quarters, Annual bluegrass

Perennial Weed: Lives for two or more years; plants grow as long as conditions are favorable and frequently die back to soil level with hard frost; new growth emerges at the start of the growing season, originating from roots or stem remains; in warmer regions, some perennial weeds can be green year-round.

Fact: Annual weed seeds can lie dormant in soil from 4-40 years.

Timing

With pre-emergent herbicides, you’ll want to apply the chemical prior to the time weed seeds start germinating, which can be spring or fall depending on the type of weed. For example: cool-season weeds, such as Annual Bluegrass, are usually best controlled with a late summer to early fall application. If you apply too early, these herbicides will have degraded and are useless when seeds start to germinate. Most pre-emergent Crabgrass killers remain active in soil for 6-8 weeks. If you apply too late, the herbicide will not affect weeds that have already germinated.