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will a composter kill weed seeds

If you enjoy it, that’s fantastic. I love the smell, look and taste (well, maybe not taste) of finished compost. I made some nice-looking stuff myself this year and just sifted it the other day.

My bet is that few gardeners reach that lofty, “proper” status.

The winter freezes come once-a-year and kill all the weeds. They fall to the ground and rot into the soil, which improves it.

My answer was:

I view this as a feature, not a bug. Sometimes I just let compost piles turn into garden beds since there are so many volunteer edibles coming up.

To those about to compost, I salute you!

Those pumpkins grew as volunteers from a compost pile a few years ago. Granted, it wasn’t a regularly turned compost pile, meaning they probably missed the hottest part of the heap, but how many of you turn your compost regularly? And I’m going to bet that you still had little tomatoes or weeds pop up in it. Come on, admit it!

If you want to use weeds to feed your gardens, you’ll have much better luck in a no-till system where you throw a pile of seedy weeds on the ground. Then, cover them up with mulch … and then, DON’T TILL!

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 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.

How Weeds Survive

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.

For hot composting to fully kill all weed seeds and roots, follow these tips:

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.