Composting Lawn Mowings that have been treated
Lawn mowings are an important ingredient of a home compost heap.
They generate heat to make the heap work faster and
they provide moisture. They should always be layered with more
fibrous material like weeds or dead stalks so that they don't
compact into a slimy mess.
Some lawn treatments contain herbicides that can persist for some
considerable time, even when they have been through a composting
process. This creates a dilemma for gardeners as these lawn
clippings are not suitable for either home composting or to put into
a green waste collection.
The herbicide clopyralid is the one most likely to cause
problems for gardeners. It is a common ingredient of
domestic lawn care products and is sufficiently persistent that it
is banned in New Zealand and some parts of the U.S.A.
If buying herbicides, read the ingredients so that you know whether
or not clopyralid is one of them. Also read the instructions
carefully to find out how the manufacturers recommend that you
dispose of the grass clippings. From February 2014 the labels on
lawn care products containing clopyralid will have to read:
‘After treatment, leave the clippings from the first
mowing on the lawn. The next three mowings should be composted well,
for at least nine months, before being used as a mulch. Do not
dispose of the grass clippings via council composting schemes.'
It is vital to follow these instructions.
Even better is not to use clopyralid at all and then you will have
If you employ a lawn care company insist on knowing exactly what
their products contain. If they won’t tell you, you will have to
decide whether or not to take the risk. Make sure that they are
disposing of your lawn clippings responsibly, even if this incurs an
If you are composting any lawn mowings that have been treated with a
herbicide, or with a fungicide or moss killer, it is safest to
compost them for at least one year, and preferably two, before using
them in your garden. Council composting schemes are designed to work
quickly and at high temperature but the speed of the process does
not allow pesticides like clopyralid time to break down and cease to
The simplest and safest course of
action is to use no lawn care treatments at all and to enjoy a
diverse lawn rather than a sterile monoculture.
ON NO ACCOUNT FLY TIP OR THROW TREATED
LAWN MOWING INTO A FIELD.