Bumpy Lawn? – Turfgrass Science at Purdue University

Bumpy Lawn?

Lawn seem bumpier this spring when you first mowed it? Bumpy, difficult-to-mow lawns can be caused by either above-ground factors or below-ground soil factors. If the bumpiness is due to patches of incompatible species of coarse, bunch grasses like tall fescue or orchardgrass growing in a stand of predominantly Kentucky bluegrass or perennial ryegrass, apply Roundup to kill the coarse grass and reseed. If bumpiness is caused by moles, rolling will smooth the mole runs, but trapping is the only way to remove the moles (refer to http://www.entm.purdue.edu/entomology/ext/targets/ADM/ADMPDF/ADM-10.pdf). Most lawns are bumpy because of the natural settling of soil over time. Professionals will apply thin layers of sand or soil over finely manicured turf and then use modified brooms to move the topdressing down to the soil surface. This topdressing will eventually help to smooth out minor undulations over many years while not harming the turf plants. On golf greens, they’ll apply about 1/32″ of topdressing at a time, and up to 1/4” of topdressing each time on higher mowed athletic fields or home lawns. If the lawn is in really bad shape, it is better to start over. Kill it with a non-selective herbicide like Roundup, till the soil to two to 4” deep, work it smooth, and allow it to settle with rain, irrigation, and/or time (the more time to settle the better). Then work it smooth with shallow raking once more after it settles and seed this fall. This settling part of the process is regularly overlooked by contractors and homeowners anxious to see grass, which usually results in a bumpy lawn down the road.


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