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.
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.
How Weeds Survive
For hot composting to fully kill all weed seeds and roots, follow these tips:
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.
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.
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.
In addition to keeping seed heads out, plants that reproduce from their roots should be avoided as well. A great example of this is Canadian thistle.
To some, dandelions are a weed. But to others, they are an incredible pollinator plant, attracting bees, butterflies and more. And to still others, they are a tasty food source as well.
So who is right – and who is wrong?
Some consider the dandelion to be a weed, others a delicious addition to a salad!
When And How To Use Weeds To A Compost Pile
But there are also many who think weeds are extremely beneficial to a pile. And that composting them not only allows you to make more compost, but a compost that is more balanced and nutrient filled.
Canadian thistle can be a nightmare to eradicate from flowerbeds and gardens. Its long, tenacious roots can produce hundreds of runners and buds to create a seemingly endless supply of new plants.
That is, of course, as long as you are using a bit of caution when adding them to your pile!
Putting Weeds In A Compost Pile
And then there is clover. To many homeowners trying to keep an immaculate turf yard, clover is a weed. But clover as a plant can actually be extremely beneficial on so many levels.
So does that mean this “weed” can go in a compost pile?