Two small lawns at the front of the house were always left unmown until the autumn.
From the economist.com
Daffodils can be planted in grassy meadows that are left unmown until June.
From the washingtonpost.com
Inside the unmown turf many small amphibians will shelter from hot weather.
From the guardian.co.uk
Very glad to read that there are now areas of unmown grass and beehives at the Botanic Gardens.
From the guardian.co.uk
This is already done on the Bristol Downs, where areas are left unmown, allowing longer grass and wildflowers to grow.
From the guardian.co.uk
Go find out what the real world is like, the earth, the air, the trees, the unmown grass, the smell of the woods.
From the guardian.co.uk
Other developers, such as the Marlin Group, have gone out of business in the 13 years Morgan has lived in Gulf Harbour, leaving common areas neglected and lawns unmown.
From the nzherald.co.nz
There in the huge burial ground where descendants of the sage are still being interred, winding paths lead between the tree-shaded tombs, most of the ground unmown and speckled with wild flowers.
From the guardian.co.uk
More examples
(used of grass or vegetation) not cut down with a hand implement or machine; "uncut grass"; "an unmown lawn"