Spend less time pulling weeds each year and learn how to keep weeds out of your garden. Start today with this weed prevention guide by Gilmour! Cover crops differ from ‘regular’ crops in that they are grown solely so the soil is covered, rather than for harvestable things. Cover crops are used by lots of folks – grain farmers, vegetable farmers, flower farmers, and they offer lots of soil benefits, as described in this blog. But they can also help control… Learn how to kill weed seeds in soil to prevent weeds and other invasive grasses from continuing to sprout every year.
Weed-free Gardening: Learn How to Prevent Weeds from Growing Before They Start!
When’s the best time to pull a weed? Yesterday. When’s the second best time? Now.
It’s an old joke, but there’s actually a lot of truth to it – the earlier you eliminate a weed, the less of a chance there is for it to multiply and take over the entire garden.
A weed is simply a plant growing where it’s not wanted. After all, one person’s wildflower is another person’s weed.
There are your usual suspects, those names that come to mind instantly when talking about weeds: dandelions, thistles, crabgrass and chickweed. But just what makes these – and others – such effective nuisances?
Weeds are naturally gifted with characteristics that let them spread easily. These characteristics include:
- Generous seed production and establishment
- Seeds that remain dormant for long periods of time
- Ability to occupy areas of high traffic
Weeds compete with grass and garden plants for space, light, water and soil nutrients. Not only do they look bad and have the ability to take over quickly, they’re also the perfect hosts for disease and insects. Before you know it, one weed can turn into many little thieves robbing your plants of their health.
How to Prevent Weeds
The best way to prevent weeds from spreading throughout your garden is to stop them before they take root. Knowing how to prevent weeds means understanding the task is not a one-time job, but rather a continual garden chore. But even those who pull weeds begrudgingly do so knowing that preventing weeds as they appear, or quickly after they’ve sprouted, takes a lot less time than removing an established weed infestation. Consider taking the following steps for a weed free gardening experience.
You can’t avoid tilling or hand cultivating when creating a new garden bed. It’s the best way to aerate the soil and incorporate organic material. What you don’t see is the buried weed seeds lying dormant just under the surface of the soil. Moving them to the top of the soil wakes them up and boosts them into germination. Once you’ve established a new garden bed, avoid unnecessary tilling and cultivating unless absolutely necessary.
If you’re looking for how to stop weeds from growing in the first place, consider a chemical option. Pre-emergent herbicides stop weed seeds from germinating. They’re tailored to target specific combinations of weeds or weed families. Simply apply the pre-emergent to your garden before the weed seeds begin to germinate – in early spring or after cultivating. Pre-emergent is activated by water, so after treating the area, be sure to give it a good soak with Gilmour’s EZ Click Control Watering Nozzle set on the garden setting. The water application draws the herbicide down to the seed level for the best results.
An effective and natural option to prevent weeds from taking over your garden is through the use of mulch. Apply a thick layer of organic mulch approximately 2 inches deep in the garden area – take care to avoid the base of individual plants and shrubs. Not only will mulch help the soil retain moisture, it also smothers out any small weeds and creates an unfriendly environment for tilled up weed seeds. While non-organic mulches (such as landscaping fabric and plastic) last much longer than organic mulches (like pine needles, cedar and leaves), they don’t break down to create a healthy soil environment.
Weeds just love the open, sunny spaces between garden plants. Plant vegetables, flowers and shrubs at the closest recommended spacing. Consider using block spacing instead of growing in rows to eliminate the open areas weeds tend to pop up in.
Young plants from the local nursery can introduce new weeds to your garden. Weed seeds are great at spreading, even in a nursery environment. Inspect all new transplants closely to ensure they aren’t bringing in any undesirable friends. If you spot seeds or sprouts, simply pull them out before transplanting into your garden.
It can seem endless, but consistently weeding your garden will pay off. For every weed remove before it goes to seed, you effectively eliminate hundreds of its offspring. Commit to a weeding schedule and stick to it. The perfect time for weeding is while the soil is moist and plants are young. Gently pull weeds at their base (disturbing as little soil as possible) and discard away from the garden. If you encounter difficult roots, insert a sharp knife or Cape Cod weeder into the ground to sever the weed from its roots without disturbing the ground or mulch around it.
If you water the entire garden, open spaces will become the perfect breeding ground for weeds. Deprive weeds of water by using a soaker hose to add moisture just where it’s needed – at the base of garden plants. By only watering these areas, you narrow down where weeds may pop up.
Many vegetable gardens lie dormant during winter months. Some annual weeds actually pop up during cool weather, like chickweed and deadnettle. You may be asking yourself how to prevent weeds from growing in gardens without any plants or mulch. Keep these weeds from germinating and taking over your yard by planting a little bit of competition. Cool season cover crops, like ryegrass or clover, create a barrier for weeds by competing for light, water and nutrients. Simply till them under in early spring to introduce organic material and nutrients into the soil.
When creating the perfect environment for your lawn and garden, you’re unfortunately crafting the ideal location for weeds to thrive. But knowing how to prevent weeds in garden areas is actually pretty simple when following these steps. Take the time now to prevent weeds from taking root and save yourself hours of weeding in the future!
How can you prevent weed seeds from germinating in your garden?
Cover crops differ from ‘regular’ crops in that they are grown solely so the soil is covered, rather than for harvestable things. Cover crops are used by lots of folks – grain farmers, vegetable farmers, flower farmers, and they offer lots of soil benefits, as described in this blog. But they can also help control weeds! Let’s explore how.
First, let’s think about the life of a weed seed. Better yet, let’s pretend we are a weed seed trying to grow in your garden. We’ll start sitting in or on the soil. One of the biggest threats to a seed is something most people don’t normally think about: getting eaten. Mice, crickets, beetles, ants, birds (including chickens) – these things all love to eat the seeds sitting in the soil. Often the seed-eaters are themselves constantly in danger of getting eaten. A cover crop provides protection for seed-eaters. It’s harder for a hawk to see a juicy mouse running along the ground if there’s a cover crop. The mice protected by the cover crop will eat a lot more seeds.
Seed-eaters such as mice can hang out and eat weed seeds under cover crops, safe from predators. Credit: Gina Nichols
Pretend you, the weed seed, didn’t get eaten. It’s time to think about germinating. But you, the weed seed, can only germinate if you get the right ‘cues’. Weed seeds are incredibly smart. A lot of weed seeds will only germinate when they sense ‘pure light’. Light changes as it passes through green leaves. Weeds don’t want competition, so they will wait until there are no other living plants around before they germinate. So, what if you planted a cover crop? The cover crop, alive or dead, is blocking that pure light from hitting the soil, where you and your weed seed friends live. You might never get the cue to germinate.
Another cue seeds look for is large swings in temperature. If the soil gets really warm during the day, then cools back down at night, this is a cue there isn’t anything trying to compete with it. Under a cover crop, the soil is shaded during the warm parts of the day, so the temperature swings are much less drastic. You might sit there waiting for a cue for a long time. But the longer you sit there, the higher the chance you’ll get eaten by one of the seed-eaters.
Let’s say you managed to get all the cues you needed to germinate. Congratulations, you are a weed seedling! But your fight is just beginning. The cover crop is hogging a lot of the things you need – light, water, nutrients – it’s stealing resources. And the cover crop is bigger than you, you’ll most likely just get the ‘leftovers’. The cover crop is making your life hard, so you are not going to flourish. And again, there is the threat of being eaten. Mammals love to eat tender little seedlings, and again they love to hang out under the protection of the cover crop, so your chances of survival aren’t great.
As you can see, using a cover crop can make the life of a garden weed much more difficult. In fact, many community gardens plant cover crops in plots that don’t have an owner, just to prevent weeds from taking over. To recap, cover crops can prevent weeds by:
- Providing protection for seed-eaters
- Preventing weed seeds from germinating
- Competing with weeds for resources
Are you sold? Here are three ways you can start integrating cover crops into your garden.
A simple way to get started is to plant a winter rye cover crop in the fall (October/November) as you put the garden to bed. Many gardening seed companies offer winter rye seeds. It’s a hardy plant that survives most winters if it gets to be one soda can tall before winter truly sets in. It also puts a satisfying ‘green’ in the garden during months that can feel dreary.
You want fall-planted cover crops to be about one soda can tall before Thanksgiving. Credit: Gina Nichols
If you are reading this in December, you might think you’ve missed your cover-cropping chance. You’re wrong! You can plant an early-season cover crop such as oats and hairy vetch as early as March. Good garden areas for these include places destined for crops you’ll transplant in the summer (pumpkins, eggplants, tomatoes), or pathways you want to keep from getting weedy.
If it gets to summer and you find you have some empty space, buckwheat is an excellent summer cover crop. It grows quickly, bees love the flowers, and is easy to kill by mowing or pulling.
For all cover crops, you need to make sure the cover crop is dead before you plant your harvesting crop. Some cover crops will die if you mow them, but others need to be pulled (you can place the pulled plants back on the ground to keep it covered), crimped (imagine stomping on the plants to break their stems), or tilled. If the cover crop is still alive, it will compete with the main crop for nutrients and light, which you don’t want.
A happy garden area goes into the winter covered by a winter rye cover crop at Mustard Seed Community Farm in Ames Iowa. Credit: Gina Nichols
Some other common cover crops are clovers, peas, tillage radish, mustards, barley, wheat, and Sudan grass. Many gardening companies also offer seed mixes. Once you start using cover crops you might find they are just as exciting as the food-producing plants in your garden. As a rule of thumb if you see bare soil you might have an opportunity to use a cover crop, the quiet weed fighter. Happy cover cropping!
Answered by Gina Nichols, Iowa State University
This blog is part of Crop Science Society of America’s Seed Week celebration. Why celebrate seeds? Anyone who plants a seed is investing in hope. That’s one of the attractions of seeds. For the gardener, it could be hope for a beautiful flower, or perhaps a delicious zucchini squash. For our farmers, seeds are the hope of this year’s yields of produce, cash crops or forage. No matter the size or shape of the seed, they all can bring forth new life. At Crop Science Society of America, we hold seeds in very high regard. Please visit our Seed Week webpage for news stories, blogs and more information about seed research and facts.
Please visit our Seed Week webpage for more information.
Read the other blogs in our seed series!
About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.
How to Kill Weed Seeds in Soil [5 Easy Methods]
To kill weed seeds in soil you will have to apply one or more of the following methods:
- Heat soil to temperatures high enough to kill weeds seeds
- Force seeds to sprout and destroy growing weeds
- Apply chemical or natural weed killers that prevent weeds from sprouting
- Use flame weeding to destroy weeds and seeds at once
- Layer mulch in garden areas to suppress weed sprouting and attract insects that eat seeds
With this arsenal of tricks for killing weed seeds before they sprout, you can stop the spread of weeds in both your lawn and garden.
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5 Tips for Killing Weed Seeds
Rather than spending time and effort battling weeds as they sprout, attack weeds at the source by killing weed seeds. Each of these methods destroys weed seeds, which ensures you won’t have to battle recurring weed invasions. Try these ways to get rid of weed seeds yourself.
Soil solarization is a very powerful method for killing weed seeds. Weed seeds begin to die if soil temperatures surpass 108 degrees, with full seed death ensured by soil surface temperatures of 140 degrees or more. Solarization uses clear plastic tarps to trap heat at the soil surface, killing weed seeds within the tarped area. To solarize an area, follow these steps:
- Clear the area of all vegetation through use of a hoe or other garden implement. Remove any woody stumps
- Till the soil to further break up any weed root systems left behind.
- Rake away all vegetation residue
- Water the tilled and cleared soil with a garden hose until it is damp.
- Lay a sheet of clear plastic over the area. Weigh it down tightly at the edges
- Leave the plastic in place for at least two months.
Solarization is the best method to reclaim a weedy garden or other area. It is a “clean slate” for your soil, because seeds will be destroyed by the solar heat trapped beneath the plastic.
It is typically tough to implement solarization in large areas and is not usually suitable for use in lawns, where you may want to preserve grass or other plants. Pre-emergent weed killers and flame weeding are much better for use in lawns.
Till and Kill
Weed seeds can lie dormant in soil for decades and are only “activated” when brought to within an inch of the surface. One method to rid soil of dormant weed seeds is to force these dormant seeds to sprout, then attack them with a powerful natural or chemical weed killer. To do this:
- In spring, till the affected area. Tilling brings dormant seeds to the surface
- Water the area for 1–2 weeks with a sprinkler or soaker hose
- When weeds begin to sprout, apply the weed killer of your choice
This is another “clean slate” method, where you force weed seeds to show themselves and then kill young weeds before they mature and cast seeds. Because of the invasive tilling step, it is not best used in areas with desirable grasses and plants.
Use Pre-Emergent Weed Killer
Pre-emergent weed killer stops weeds in their tracks. It works by attacking weed seeds just as they begin to germinate, killing them before they even poke above the surface. It’s a weed killer so good, the only sign it’s working is that there will be no new weeds at all.