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do weed seeds die in compost heaps

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

If you till, you’ll bring those seeds up to the light and warmth. They’ll go crazy in your eggplants. However, beneath a layer of mulch, they’ll eventually rot away safely.

But Let Me Back Up. What Prompted Today’s Post?

My composting methods have gone from complicated to simple over the years. I’ve realized creating perfect compost doesn’t really matter.

There was a comment that prompted today’s great big post on weed seeds in a compost pile. Four words that led to 1,145 words (give or take):

My favorite method is to keep them out of the compost pile and gardens altogether.

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.

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

Composting Issues

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.

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.

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.