Most individuals mow their lawns when it gets “too high” or when it starts looking shaggy. Have you ever wondered how to determine the best to mow the lawn? Ideally the lawn gets mowed when no more than one third of the grass blade will be removed. This means that if your lawn mower is set for 3.5 inches, a good height for most lawns, you should not let it grow to more than 5.5 inches before mowing again.
There are two good reasons for following this 1/3 removal guideline for mowing. The first is that it promotes good plant health. Cutting off only 1/3 of the grass often requires more frequent mowings. The more frequent mowings stimulate lateral, sideways, growth that fills in the lawn more effectively producing a thicker denser lawn that is more attractive and resistant to weed invasion. If more of the grass is removed at mowings the grass plants will grow taller, generally resulting in a less dense lawn. The down side of this is that it will likely mean having to mow every 4-6 days during the spring when grass is growing rapidly rather than just once a week. On the other hand, when it is growing less rapidly later in the season it may be that mowing is only necessary once every 10-14 days.
The second reason for utilizing the 1/3 removal guideline is for grass clipping management and environmental sustainability. If you are bagging your lawn, to avoid large unsightly clumps and even the possibility of killing the living grass underneath the clumps, you are most likely not following the 1/3 removal guideline. By following the 1/3 removal guideline, the clippings are cut small enough that they can be easily distributed across the lawn with a side discharge or with a mulching mower. It should not be necessary for you to bag your lawn clippings. One good reason for not bagging is that the nutrients in the mulched grass clippings are recycled into your soil and can reduce your fertilizer needs by a reported 25-33%. Also, bagging your lawn clippings is detrimental to the environment in that they generally end up shortening the life of landfills.
There are times when you go on vacation or it seems like the rain will never end and you are unable to mow. If this does occur, remember the 1/3 removal amount is a guideline. Bag your lawn when you can mow it and then get back to the 1/3 removal rate as quickly as possible.