Getting the lawn ready for winter

I had several calls to the office about preparing a lawn for winter. When dealing with lawns, regardless of the time of year, there are four considerations:

  • mowing
  • irrigation
  • fertilization
  • Weed control
  • Other – occasionally we also have to take care of compaction and thatched roofs

Some of the recommendations will change as the fall season begins.


Throughout the summer we keep preaching that the lawn should be cut high. The longer the leaf blade, the deeper the roots. For Kentucky bluegrass, the best height is 2.5-3.5 inches. This one practice will save your water bill and reduce weed pressure on your lawn. Keep mowing up until the last mowing.

The final mowing should be done after the grass has stopped growing – likely mid-October to mid-November in most parts of eastern Idaho. Every year is different and Ashton is different from Pocatello. This last mowing should be short – 2 to 2.5 inches long. This last mowing (which can also have a lot of tree leaves) should be packed in bags.


Proper watering in autumn will save you a lot on your water bill. Water the same amount, just increase the number of days between waterings. You shouldn’t water more than once a week at the moment. In cold temperatures, timing becomes a problem. The last watering should be around the time you last mowed (before the ground freezes so your sprinkler system can be winterized) so that there is enough soil moisture to survive the winter.


Top dressing is probably the most important for lawn health and spring green. This final fertilization should be half a pound of nitrogen per 1,000 square feet and should be applied just before the final watering. Too much autumn fertilizer promotes some winter diseases.

Weed control

Winter annuals are only young seedlings at the moment and are easier to control at this young stage. Biennial and perennial weeds such as muskrat thistle, bull thistle, dandelion, Canadian thistle or morning glory transport nutrients to the roots when the days get shorter and colder. Fall is a great time to bring systemic herbicides down to perennial roots. Weed control in the fall also reduces the number of weeds in the spring.


If you’re having compaction or matting problems in your lawn, you might want to aerate this fall.

Compaction occurs in high-traffic areas. This will prevent oxygen from reaching the roots and causing them to die.

Straw are the tall lignin grass stalks that do not break down very quickly. There could be several reasons for this, but most of the time it can be attributed to poor soil health practice.

Core ventilation increases the oxygen content of the soil and helps combat both compaction and matting situations. If you find that ventilation is needed, be sure to use a core aerator that will leave the plugs on the soil surface. Just sticking spikes in the ground actually increases the compaction.

If you take a few steps this fall, you can have an easier spring.

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