can you compost weeds?
Yes, but only weeds pulled before they set seed — seed heads and running roots need a genuinely hot pile or the trash.
breaks down in 1–3 months for soft green weeds in an active pile
C:N ≈ 20:1
which bins can take it?
- hot pile yes
- cold pile caution
- worm bin caution
- bokashi no
- tumbler caution
- curbside yes
- cold pile: Seeds and root fragments come through a cool pile alive — with this setup, pull weeds before they flower.
- worm bin: Fine in small amounts, but a worm bin never gets hot enough to kill anything you put in it.
- tumbler: A drum rarely holds 140°F long enough to kill seeds — load it with weeds pulled before they flowered.
why?
Green weeds are nitrogen-rich plant tissue that behaves like any other garden green once it hits a pile. The trouble is the parts built to survive: most weed seeds need about 30 minutes at 140°F to die, and perennial roots such as quackgrass rhizomes sprout happily in the cool, damp outer shell of a backyard heap.
how to prep it
- Pull weeds before the flowers open
- Shake soil off the roots so the pile heats instead of ballasting
- Bury weeds in the pile center, never on the surface
watch out for
- Seeds survive anywhere a pile stays cool, and the outer 6 inches almost never reaches killing temperature — turn the edges into the middle at least twice.
- Weeds sprayed with a broadleaf herbicide in the last few weeks can carry residue into finished compost.
- Bindweed, quackgrass, and Bermuda grass regrow from root fragments; dry those on pavement until brittle first.
often confused with
- Weeds with seeds — Once seed heads have formed the answer changes — that material needs sustained heat, not just a pile.
quick answers
Does composting kill weed seeds?
Hot composting does, at temperature. USDA organic rules use 131–170°F held for 15 days with five turnings as the benchmark for killing seeds and pathogens; a pile that never steams is not doing this.
Can I make weed tea instead?
Yes. Drowning weeds in a covered bucket of water for three to four weeks rots them to sludge and finishes off the roots, along with most of the seeds. Strain the liquid off as a dilute feed and compost what is left.