Q. I live in a subdivision with 400 townhomes and a fair amount of grass that the HOA maintains. The lawn crew does a couple of things that I question. They keep the grass mowed pretty short; 1-1/2 inches. Shouldn't they wait until it gets about 3 inches and then cut only 1 inch off? Wouldn't this minimize evaporation? They are collecting the clippings and discarding them. Wouldn't it be better for the lawn if the clippings fall back on the grass? Doesn't the nitrogen recycle back into the lawn?
A. They should be recycling the clippings back into the lawn and mowing higher. This will require that they use recycling mowers, a special blend of fertilizer with half of its nitrogen in the slow release form and closer lawn management.
Mow tall fescue no closer than 1 1/2 inch at any time and 2 inches is better. This gives them 1/2 inch of growth they can remove safely each mowing. These grass blades contain a lot of fertilizer that end up in the landfill so it is better to recycle them back into the lawn.
If removed clippings are an inch long, this tells me the nitrogen fertilizer applied is excessive. No more than 1/3 to 1/4 of the grass blades should be removed in one cutting. Measuring the average length of clippings is a good way to determine if nitrogen fertilizer is needed by a lawn or not.
Mowing is important for controlling lawn diseases. Grasses are unique because they push growth from the bottom of the blade; the oldest growth is removed when mowing. Old-growth contains more disease problems than the newest growth.
Lawn clippings can and should be returned to the lawn. If they do this successfully they must use recycling mowers and a quality lawn fertilizer. Returning lawn clippings to the lawn substitutes for one fertilizer application every year. Recycling lawn clippings back into the lawn improves its general health because lawn clippings are composted back into the soil, releasing nutrients.
Recycling mowers have a unique blade and a unique deck design that provides greater lift and causes lawn clippings to be “chopped up” more effectively than with traditional mowers. Traditional mowers retrofitted with recycling blades will work but they are not as efficient as recycling mowers.
If a recycling program is done correctly, you will not see any residue from lawn clippings left on the lawn after mowing.
Fertilizers used with recycling mowers are unique. They must have a large percentage of their nitrogen in a slow release form or the fertilizer should be applied in much smaller quantities, more often. Their greater cost is offset because less fertilizer is required.
Where I don’t agree with you is on water conservation. The research is conclusive that lawns mowed higher use more water than lawns mowed shorter. However, lawns with a deeper root system are more drought tolerant. So it is a trade-off.
|Lawns that are mowed higher have deeper root systems. This makes them more drought tolerant but they also use more water.|
This is misleading because the difference in water use between a closely mowed lawn and one that is mowed taller is not large. It is more important to have an irrigation system that is designed and maintained correctly and water applied when winds are minimal and adjusting your lawn watering schedule monthly during the spring and fall months. Lower water use is tied more closely to management of the lawn and irrigation system, not the root depth of of lawn grasses.
Mowing a lawn higher has other benefits. Lawns mowed taller have deeper roots. Deeper rooting means better drought tolerance. Here is the rub. Improved drought tolerance alone has no relationship to low water use. It could be argued the opposite; they use more water.
|Water use of lawns in inches per day as the seasons change in Las Vegas. Months are January=1 and December=12|
Bottom line. Lawn maintenance companies should not be bagging lawn clippings but returning them to the lawn using recycling mowers. They must be careful in applying nitrogen to lawns. Over applying nitrogen fertilizers causes lawn recycling programs to fail.