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kill weed seeds

Cover your planting areas with mulch and you’ll keep weed seeds from coming into contact with the soil in the first place. Mulch will also keep sunlight from reaching seeds that are already underground, so they won’t get a chance to sprout. Mulch offers the added benefits of retaining moisture and breaking down to enrich your soil. And it looks really pretty, too.

Smother weeds and prevent new ones from growing by covering them with old newspapers. A thick layer of newspaper will keep sunlight from reaching weed seeds, so they can’t sprout. Wet the soil first, and then lay your newspaper down, wetting it thoroughly again before covering with mulch. This is a great way to recycle, and as a bonus, you’ll encourage earth worms to come and stay.

Cornmeal

Did you know that corn gluten meal is birth control for seeds? Sprinkle it on your garden and it will keep weed seeds from germinating and growing into plants. Of course, corn gluten meal will keep any seed from germinating, so don’t try this on your vegetable garden until your plants are established and you’ve finished planting seeds.

Apply vinegar with a spray bottle, pump sprayer, or brush. Like other natural herbicides, vinegar cannot differentiate between weeds and other plants. Do this early in the morning, when there’s little wind, to avoid contaminating nearby plants. Vinegar’s killing properties are activated by the sun, so try this on a cloudless day, which also ensures that rain won’t wash it off before it works its magic.

You can rid yourself of weeds the old fashioned way—pulling them by hand—if you’re vigilant. Wear a dedicated pair of gardening gloves for the task to avoid inadvertently transferring seeds elsewhere. Good gardening tools like a claw or sharp trowel can help you loosen the weed roots from the soil first. Pulling a weed completely out by the root is the only way to ensure it will not return.

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.”

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.

Preparation

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.

When you cut slits in the landscape fabric and install new plants, be careful that you don’t get dirt all over the landscape fabric. After all, why prepare a home for airborne seeds? Sure, you will be applying mulch. But airborne weed seeds can wend their way through mulch particles. If they find dirt, then they are “weeds waiting to happen.”

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.

C:N ratio: To maintain the correct C:N ratio, build the pile with alternating layers of brown matter such as dead tree leaves, and green matter such as grass clippings. Adding equal amounts of green matter (grass clippings, kitchen waste) and dry matter (dry leaves) will often achieve this desired ratio.

Most gardeners have a static compost pile. They believe that composting consists of filling the pile, waiting a few weeks, and then magic happens—the compost is ready. In reality, most compost piles are merely trash heaps of garden and kitchen waste.

Turning: Periodically mix the materials within the pile to introduce more oxygen and distribute the moisture evenly (Fig. 3). To add as much air into the pile as possible, break up any clumps, and move the drier material from the outer edges into the center.

How does composting reduce weed seeds?

pH: pH meters are available in garden centers and can be used to estimate the pH level of the compost pile. However, an easy and more practical way to tell whether the compost pile is “cooking” properly is by its smell. If the compost pile smells sour or like a rotten egg, the pH is not correct. A compost pile at the proper pH should smell earthy, like freshly dug garden soil.

Proper composting occurs under the following conditions:

These high temperatures are the key to killing weed seeds in a compost pile. In general, more seeds will die the longer that the temperature in the pile remains within this range (Table 1).

Composting occurs when organic materials—such as yard trimmings, food wastes, and animal manures— decay to form compost, an earthy material that can be used to improve garden soil. Compost benefits gardens by: