Can I compost the grass clippings after a lawn treatment?

I am often asked by customers if they can compost the grass clippings if it is being professionally treated. The answer is, it depends!

My regular lawn treatment programme involves the application of a herbicide to control lawn weeds. Some of the professional herbicides I work with are designed to prevent germination of weed seeds. This chemical can be residual. Trace amounts can be passed from the grass clippings to the compost and then to other garden plants. This risk is very small, but does exist, so it is wise to take precautions against contamination.

Compost the grass clippings from a lawn
Grass clippings being composted from a lawn.

My advice is simple. If your lawn is being treated for weeds, don’t use fresh grass clippings on any tender plants, seeds or vegetables. This will prevent leeching of herbicides into these plants. If this is not possible, then dispose of your grass clippings in the council green waste bins. They compost at much higher temperatures which breaks down lawn herbicide compounds.

Compost the grass clippings

If you want to use your treated grass clippings in the garden, mulch them around established shrubs, or compost them on an established compost heap for at least six months. This will break down any herbicides and they will then not cause any harm to garden plants.

I recommend doing this for at least six weeks after a herbicide treatment. After that, the chemical should no longer be present in the grass.

My use of herbicides does vary from treatment to treatment. If you do not have any weeds and are treated regularly, I usually just spot weed, this reduces herbicide use even further. At your request I can even swap out your herbicide spray for a seaweed spray which is very beneficial to all areas of your garden. This will not reduce your lawn weeds though!

If you have had your lawn treated with a fungicide, I recommend not composting your grass clippings in your home compost bin for six weeks. This will prevent the chemical from affecting the composting processes in your bin. They will be fine in your council composting waste though as this is carried out at a much higher temperature.

With all lawn treatments, communication is the key. If you are at all concerned with any treatment I am applying to your lawn, please get in touch and I will be able to explain any issues and modify your treatment according to your wishes.

Strip of lawn and a nice plant border
A lush, green, weed free lawn.