How to Compost Weeds Without Actually Planting Them

For those new to composting, figuring out what goes in and what to leave out can be daunting. And if you’re composting, chances are you’re also doing other things in your yard, like gardening or landscaping — which means you’re dealing with weeds.

So naturally, that raises the question of whether it’s possible to compost the weeds you pull without accidentally planting them and causing more to grow. Fortunately it is, and here’s what you need to know.

How to compost weeds

When it comes to composting weeds, Linda Brewer, an instructor at the Oregon State University Extension has a rule: Never put anything into the compost pile that you don’t want more of — including weed seeds and diseased plant tissues. So to avoid doing that, she takes the time to remove the seeds (even ones that are immature) and the roots of the weeds before composting them, and instead, puts them in the trash.

As far as the weeds’ roots, you can also try a process called “desiccating,” which is essentially baking your roots using the heat from the sun. Instead of throwing them away, lay the roots of your weeds on concrete or corrugated iron — the idea is to keep them off and away from the soil. Let them bake there for two to three weeks in the summer, and after that, the roots should be hard and safe to include in your compost pile.

Weeds to avoid composting completely

There are some weeds that are so good at spreading, that even if you remove the seeds, they can still (and often do) somehow manage to find a way to grow. A few examples of these include:

• Horse tail (equisetum)
• Bindweed
• Canadian thistle
• Morning glory
• Buttercups
• Bermuda grass
• Oxalis
• Quackgrass
• Crabgrass

If you have a hot compost pile, the heat may be enough to prevent the seeds and roots of these weeds from growing. But because most home gardeners have cold compost piles, these weeds are best to leave out.