Composting Weeds

Composting Weeds

Editorial for In the Garden, CV Record 5 June 2012

Yikes, the weeds are getting out of hand! And what lush growth! I would love to have that rocket fuel in my compost but I don’t want to spread the seeds for extra years of weeding. What to do? Well, there are various ways to compost weeds without creating a future calamity.

Rule 1: Compost weeds before they go to seed.

Rule 2: If weeds have already gone to seed, compost them in a hot compost pile. Temperatures of 55 to 60 C (130 to 140 F) will kill most weed seeds.

Rule 3: If you are not hot composting, kill the weeds before going to the bin by drying them in the sun. Put them on a piece of cardboard or newspaper so they do not spring back to life. A few days of dry sun and the weeds are toast. The cardboard or newspaper will start decomposing and you can toss that in the pile too.

Rule 4: Quarantine diseased plants in their own compost pile. The bacteria or fungi that cause the disease are starved, poisoned or consumed by the enthusiastic compost micro-organisms. And the thermophiles, high temperature microbes, are the most lethal.

Rule 5: Noxious weeds (buttercup anyone?) can be solarized. Stuff them in a plastic bag with a little water in the sun until they turn into slime. Manure and hay are wonderful compost additives but often bring a curious assortment of weed seeds. But don’t give up on these precious resources. There are various ways to conquer the incoming weeds.

You could start one compost heap or bin for all the weedy, seedy waste. Keep another pile or bin strictly for the more weed free material such as leaves, sawdust, grass clippings, coffee grounds, etc. In your weedy bin, as decomposition progresses, turning the pile will mash weed sprouts. If you can attain temperatures of 55 C (130 F) for three days, most seeds will be destroyed without losing the beneficial microbes.

To be sure there are no seeds remaining, you can solarize the compost. But don’t get over 70 C (160 F) as that will harm the good soil life. Or you can put the near finished moist compost in a bucket or bag, let the seeds sprout, and then toss them around to mangle the sprouts. Soil life is happy, seed spouts are crushed.

Another option is to put the dangerous seedy, weedy compostables into a pit or trench. Seeds won’t sprout a foot or so underground. Just beware if you till up the pit later. You can test your compost for weediness by taking a handful, putting it in a bag moistened with water in a warm place and see what springs to life.

So go ahead and compost those luscious weeds. They are pulling rich nutrients from the deep. When composted, your garden will love the smorgasbord. Have some better ideas? Do share in the comments below.

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