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clear 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.”

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.

Weed management toolbox

“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.”

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.

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:

Weed-killing heat can also be generated using plastic. After harvest in fall, cover a planting bed with dark landscape plastic (hold it in place rocks or bricks) and leave it on over the winter. Sun hitting the plastic will heat up the soil temperature beneath to destroy weed seeds.

The best way to get rid of weeds is to pull them as soon as they sprout. This may require spending 5-10 minutes daily or every other day pulling tiny weeds, but it’s much simpler to remove them while they’re small.

6. Cut it out.

Gardeners can reduce the number of weeds in perennial flowerbeds and borders by using landscape fabric. Available in large rolls for spreading out around shrubs, roses, trees, and bushes, landscape fabric stops weeds from growing by creating a barrier that doesn’t let them reach sunlight. While various types of landscape fabric are available, most are made from woven materials, such as polypropylene, and contain perforations that allow water to seep through.

The eco-friendliest option is to add pulled weeds to a compost pile or bin, where the internal temperature will reach at least 145 degrees F to kill the weed seeds. The finished compost can then be cycled back to the garden to add nutrients to the soil.

Hot water can also kill weeds. Carefully pour a pitcher of just-boiled water directly on weeds or use a steam weeder, such as the DynaSteam Weeder (available at Amazon), to simplify the process—and reduce the risk of dripping scalding water on your feet.