Choosing planting

Can you compost "weeds"?

and if so: how to do it?

Contents

Modified the 30 November 2025 by Olivier 2 min. Difficulty: Beginner

A “weed” does not exist. Let’s say that some gardeners do not appreciate certain plants in certain places (that’s for sure!). We will rather talk about adventive plants in this case. These adventive plants include wild plants, which have their usefulness in the garden (biodiversity, food and shelter for wildlife, organic indicators…), and cultivated or uncultivated plants that have no place where they grow in the vegetable garden or elsewhere (invasive, smothering, or simply unsightly). How can we ensure that once pulled up without mercy and any further ado, these adventive plants or “weeds” still contribute a little to the balance of the garden? By composting them, of course! Indeed, all these green waste are full of water, nutrients, and minerals. It would be a shame to waste them, so we will recycle them.

→ Let’s see how to compost adventive plants and the mistakes to avoid!

composting weeds, weeds compost, adventive plants compost Some adventive plants can be composted rather than thrown away

Difficulty

Le compostage des "mauvaises herbes" peut poser plusieurs problèmes. Tout d'abord, certaines de ces herbes peuvent être porteuses de graines viables qui, si elles ne sont pas correctement décomposées, peuvent germer dans le compost fini et se propager dans le jardin. De plus, certaines mauvaises herbes, comme les chardons ou les pissenlits, ont des racines profondes qui peuvent survivre au processus de compostage si la température n'est pas suffisamment élevée. Enfin, le compostage de mauvaises herbes qui ont été traitées avec des herbicides peut contaminer le compost, rendant les plantes cultivées à partir de celui-ci sensibles à ces produits chimiques. Pour éviter ces problèmes, il est conseillé de composter uniquement les mauvaises herbes qui ne produisent pas de graines et de s'assurer que le compost atteint des températures adéquates pour une décomposition efficace.

If you incorporate seed-bearing adventive herbs and the compost heap does not heat up sufficiently, it is highly likely that you will disperse their seeds as soon as you use your compost. The seeds can even germinate directly in the compost.

Worse still, certain parts of plants can regrow directly in the compost: for example, bindweed roots or potato peels, household waste that can sometimes turn a simple compost heap into a mound of potatoes (though this can be handy at times…).

In other words, not everything can be thrown onto the compost without consideration, especially if it is not sufficiently aerated, hydrated, or does not have a good carbon/nitrogen ratio. All of this allows the compost to heat up properly, thus annihilating contaminants and seeds of adventive plants.

→ Find all of Ingrid’s tips for successfully making compost.

composting adventive herbs, adventive herbs compost, seeds in compost

Beware of seed dispersion in your compost!

How to avoid these issues?

Fresh “weeds,” like all plants, are full of water and are therefore perfect for speeding up the warming of the compost bin. You should just avoid three types of weeds in case the compost does not reach the necessary temperature to prevent issues. Therefore:

Let’s avoid, if possible, seeded plants, but you can trim the flower spikes;
Let’s avoid plants whose roots, stems, or other parts can quickly form roots and thus invade the composter: nettle roots, bindweed, potato, periwinkle, cleavers…;
Let’s avoid plants affected by diseases.

However, dry “weeds” should not be forgotten. Especially in the case of plants that can root in a compost heap. If you dry them for a few days in the sun, the risk will become non-existent: this should be done with plants that have long running roots like bindweed, for example.

If your compost heap reaches a temperature of 50 °C in its centre, you can place the three types of adventives to avoid (seeded plants, invasive ones, and diseased plants) directly in the centre of the compost heap.

composting weeds, weeds compost, adventives compost Avoid seeded plants, certain running-root adventives like bindweed, and diseased plants