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Kill weeds now; feed lawn later

This is a great time to kill weeds but a bad time to feed the lawn.

Field bindweed in lawnNow is the best time of year to kill broadleaf weeds in lawns. This includes dandelions, thistles, clovers, black medic and field bindweed (shown). As days get shorter, these perennial weeds begin channeling their nutrients down into their roots to prepare for winter. This is great, because a herbicide sprayed on a weed at this time will be channeled down into the weed’s root system, killing the entire plant.

The most effective products include a combination of herbicides. Trimec formulations will include a combination of 2,4-D, mecoprop and dicamba. Dicamba is especially powerful, but the chemical can build up in the soil and damage trees, shrubs and perennials. Limit yourself to one application of dicamba per year; and now is the best time for it.

Now is not a good time to feed your lawn. The grass plants want to prepare themselves for winter. A fertilizer application now prevents this by promoting blade growth and delaying hardening. This makes the lawn more susceptible to winter injury.

It is better to wait until mid to late October to feed the lawn. This is after the grass blades stop growing and after you have stopped mowing. This application in October is the single most valuable time to fertilize the lawn—any lawn.

You will not see any immediate effects of this dormant application, but the fertilizer will develop a stronger root system this fall and generate new buds for blade growth next spring. Turf roots grow until the ground freezes in mid November.

Written by Tom Kalb, Extension Horticulturist, North Dakota State University. The photo was made available under a Creative Commons license specified by the photographer: Colin Jacobs.

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