Weeds can be safely added to a compost pile if you make sure temperatures are high enough to kill the seeds and roots. How to Cut Weeds After Seed Heads Appear. Weeds reproduce rapidly when they grow seed heads, and they can become an eyesore quickly as well as rob your garden and lawn of vital nutrients. Seed heads contain mature seeds that typically are spread by wind and insects. Ideally, weeds are removed before the appearance of … Weeds in your garden are not only unsightly, they also are the source for more weeds to invade. Prevent new weeds from growing with Preen Weed Preventers. – Preen
Tips for Composting Weeds
Colleen Vanderlinden is an organic gardening expert and author of the book “Edible Gardening for the Midwest.” She has grown fruits and vegetables for over 12 years and professionally written for 15-plus years. To help move the organic gardening movement forward, she started an organic gardening website, “In the Garden Online,” in 2003 and launched the Mouse & Trowel Awards in 2007 to recognize gardening bloggers.
Amanda Rose Newton holds degrees in Horticulture, Biochemistry, Entomology, and soon a PhD in STEM Education. She is a board-certified entomologist and volunteers for USAIDs Farmer to Farmer program. Currently, she is a professor of Horticulture, an Education Specialist, and pest specialist.
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Compost is a great way to recycle organic material in your garden. All those spent flower blossoms, fall leaves, dead plants, grass clippings—even non-meat kitchen scraps—can be transformed into a great soil amendment and nutritious mulch, simply by throwing them into a heap and allowing the refuse to decompose naturally.
Done correctly, composting creates a sterile organic material that does nothing but good things for your garden and the plants in it. However, nearly every gardener who practices composting has occasionally experienced “volunteer” plants sprouting up in the garden where the compost has been spread.
This can actually be rather charming when the volunteers are tiny impatiens seedlings, tomato plants, or even pumpkins that volunteer because last Halloween/s jack o’ lanterns were added to the compost heap. It’s far less charming when the volunteer plants are hundreds of dandelions or tiny sprigs of bindweed or crabgrass that get into the garden via the compost you spread.
A gardener who experiences such an explosion of volunteer weeds may well swear off composting altogether, or at least stop adding weed material to the compost pile. To be clear, there is no reason to stop composting weeds. With a slight adjustment to the composting process, you can ensure that weeds and their seeds will be killed completely and won’t be resurrected where you least want them .
How Weeds Survive
In an ideal compost heap, the temperatures generated by the breakdown of plant material can get quite warm, and if temperatures exceed 145 degrees Fahrenheit, pretty much all seeds and roots will be killed. However, if the temperatures do not get warm enough—or if a portion of the compost heap does not experience sufficiently high temperatures—seeds or perennial roots can survive the composting process. When these seeds or bits of root later reach your garden inside the compost, they can—and usually do—quickly germinate or take root again.
How do you know if your compost is getting hot enough to kill all weeds? A variety of compost thermometers are available that can gauge the temperature of your pile. Experienced gardeners may simply thrust a hand into the pile. If it feels uncomfortably warm to the touch, it likely is warm enough to kill all seeds and roots in the pile.
The classic method of composting—the method purists would call the “right” way—is known as hot composting. This simply means that you turn the pile regularly and allowing it to really heat up to 145 degrees Fahrenheit or more. A properly maintained hot compost pile will kill weed seeds, as well as many other pathogens, so you can compost weeds without having to worry about them popping up in your garden beds.
For hot composting to fully kill all weed seeds and roots, follow these tips:
- Turn the pile frequently. All compost heaps have localized cool spots that are slow to break down. By mixing the pile frequently, you ensure that all material is achieving the necessary heat to kill the seeds and roots.
- Give it time. Practiced correctly, hot composting involves processing a volume of material fully until it is fully decomposed. Don’t continue to add small amounts of additional material to the heap; start another heap while the first one breaks down completely. The compost is ready to spread when turning and mixing the pile no longer causes the compost to heat up.
- Weed the garden before adding compost. Fresh compost is laden with nutrients, and if there are weeds growing in your garden, adding compost will simply nourish the weeds along with your garden plants. Make sure your garden is well weeded before adding fresh compost to the soil.
So-called “cool composting” is a more informal style of composting. It is a passive method that doesn’t involve constant temperature monitoring and mixing. In cool composting, fresh material is constantly added to the top of the heap as the lower levels are breaking down into compost. In cool compost bins, gardeners periodically remove the prepared compost from the bottom of the pile as fresh material is constantly added to the top. Cool composting is an easier style, though it can take somewhat longer.
Here are some tips to keep a cool compost pile free of weeds:
- Don’t compost pernicious weeds. There are certain perennial weeds that require lots of heat to kill, and if you don’t have the time for hot composting, it is best to keep them out of the compost pile altogether. In a cool compost pile, weeds to avoid include morning glory, buttercups, bermuda grass, oxalis, quackgrass, and crabgrass. Any garden plant that spreads by runners, such as mint or raspberry canes, should also be kept out of a cool compost pile.
- Don’t compost weeds that have gone to seed. Most annual weeds pose no problems if they are added to a cool compost pile before they are mature and set seed. But throw those same dandelions into the pile after their flower heads have produced thousands of seeds, and you may experience a dandelion epidemic when that compost is later added to the garden. If you are cool composting, weeds that have gone to seed should be thrown in the trash, not added to the compost pile.
- Prebake the weeds. Pretty much any plants, even the pernicious varieties that spread by runners, become safe for any compost pile if you heat them up to the temperature necessary to kills seeds and roots. There are a number of ways to do this. For example, you can solarize them by baking them inside a black plastic bag in the sun for a few days. Other gardeners bake weeds on a sheet of metal laid in the sun; once the weeds are baked to a dried crisp, they pose no risk in the compost heap. Some gardeners have even been known to keep an old microwave oven in the garage or garden shed, using it to “nuke” the weeds into oblivion by heating them until they steam before adding them to the compost heap.
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How to Cut Weeds After Seed Heads Appear
Weeds reproduce rapidly when they grow seed heads, and they can become an eyesore quickly as well as rob your garden and lawn of vital nutrients. Seed heads contain mature seeds that typically are spread by wind and insects. Ideally, weeds are removed before the appearance of their flowers that eventually release seeds. If some of them escape removal before they produce seed heads, they can be cut down. When you remove weeds with seed heads, you eliminate one of the biggest sources of weeds on your property.
Cut off weed flowers and seed heads using pruning shears, and dispose of them immediately. Cutting the flowers and seed heads rather than removing entire weed plants is ideal if you find weeds in your vegetable garden and don’t want to disturb your crops by yanking out whole weed plants. If the weeds contain large leaves that cover your plants, clip off all the weeds’ foliage so your crops receive more sunlight.
Cut weed plants to ground level with pruning shears or a lawnmower that has a mower bag. If you use a lawnmower, empty its mower bag into the trash immediately so that you do not inadvertently spread the weed seeds the next time you use the lawnmower.
Collect all of the cut weeds and seed heads with a rake, and dispose of them. Repeat the cutting process when the weeds grow and especially before they produce seed heads again.
Weeds Gone To Seed
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Why You Should Never Let a Weed Go to Seed
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A big reason that weeds are such effective invaders is that most of them are very prolific seeders. It’s not unusual for a single weed plant to throw off hundreds of viable seeds. If weeds are left to grow and produce new seeds, any that fall to the ground can live for years in the soil. Some can live for decades. That’s why the number one rule in winning the long-term battle against weeds is to stop them from growing at all.
Dealing with weeds you already have
If common spring-time sprouters like chickweed, purple deadnettle, dandelions, garlic mustard, and creeping speedwell have already flowered, a steady supply of summer weeds will be attempting to flower and set seed. Some of the worst summer seeding weeds include pigweed, purslane, thistle, lamb’s quarter, black medic, spurge, bindweed, Japanese knotweed, and assorted grassy weeds.
Pulling and/or digging is the most immediate, effective control. Just be sure to get roots and all or else many weeds will simply sprout new leaves from the roots left behind.
Be persistent, and you’ll eventually win – or at least gradually reduce the outbreaks by denying weeds from reproducing via seeds. Even if you can’t pull or kill all existing weeds, at least patrol enough to cut, hoe, or weed-whack any that are forming flowers or flower stalks.
Preventing future trouble
Bare soil only invites weeds, so it is best to add plants to bare spaces and add a few inches of mulch to your landscape beds to fill the space, leaving no room left for weeds.
Granular weed preventers such as Preen can go on top of mulched, planted beds to further stop new weeds before they have a chance to sprout and grow. Two to three applications per year can give season-long protection, depending on your climate and which type of Preen you use.
Preen offers many different options for controlling weeds in your landscape.
provides protection from new weeds for up to 6 months and is labeled for use around 600 plants in perennial flower beds; around groundcovers, trees, and shrubs; and in xeriscape settings and rock gardens. blocks new weeds from germinating in your garden for up to 3 months and is labeled for use around 200 established flowers, vegetables, trees, and shrubs. blocks weed seeds from germinating in your garden for up to 3 months, and gives your plants a boost of plant food for beautiful, radiant blooms. is a natural way to keep weeds from sprouting in your vegetable garden. Providing 4-6 weeks of weed protection, Preen Natural can be used around any plant, including established vegetables, herbs, and fruits.
Remember, every weed flower you prevent or eliminate now could translate into hundreds of fewer weeds you’ll have to deal with later.