Author: Dianne DeLongchamps
How do I winterize my lawn before the first freeze in Northern Colorado?
Winterizing comes down to four steps, done in this order: one last fall feeding while the grass is still green, steady mowing until growth stops, a sprinkler shutdown before the first hard freeze, and occasional watering through mild winter days. None of these steps is hard on its own. Doing them out of order is what trips people up.
Luke DeLongchamps, who runs the field side of our business, says the mistake he sees most often is shutting the sprinkler system off too early. He points out that September into October is an important recovery period for grass, and that a system can survive a light freeze, so he does not rush the shutoff.
Clean Air Lawn Care handles the fall feeding as one of our organic lawn fertilization treatment visits, and we do the fall sprinkler blow-out ourselves.
Step one: the final fall feeding
PlantTalk Colorado says to fertilize cool-season lawns with nitrogen sometime during late September to early November at lower elevations, earlier in the mountains, while the grass is still green and the soil still holds enough moisture for the feeding to soak in. PlantTalk lists a healthier root system among the benefits of a fall feeding, and it calls fall the best time of year to fertilize Colorado’s bluegrass lawns. It also says the turf must be green when the nitrogen goes on, which is why this step comes first for lawns in Fort Collins, Windsor, and Timnath.
Step two: keep mowing at a steady height
Some people think you should cut the lawn short right before winter. CSU Extension doesn’t back that up. PlantTalk Colorado’s mowing guidelines give a preferred height of two inches to three and one-half inches for Colorado turfgrass, and they say there is no reason to change mowing heights during the year. Keep mowing at your normal height as long as the grass is still growing in fall, then stop when it stops. The timing is in our post on when to mow your lawn for the last time this fall.
Step three: get the irrigation system shut down
Water left inside pipes, valves, and the backflow preventer is a real freeze risk once temperatures drop. CSU Extension’s guide to preparing a sprinkler system for winter says water expands by one-eleventh when it freezes, and that the force is enough to burst pipes and fittings. The same guide calls compressed air the only positive way to be sure enough water has been expelled, and it tells readers not to trust manual or automatic drain valves.
Two details from that guide show why a shop compressor and a quick tutorial are risky. It gives an ideal compressor range of 40 to 80 psi, with 80 psi the maximum for rigid PVC pipe and 50 psi for flexible polyethylene pipe. It also says a pressure vacuum breaker (one common type of backflow preventer) must never be blown out with compressed air. Instead, its ball valves and test cocks are exercised back and forth several times, then left in a half-open position for the winter.
The compressed-air pressure and backflow details are in our post on when to blow out sprinklers in Fort Collins, Windsor, and Timnath. This is a job with real ways to go wrong, which is why Clean Air Lawn Care handles it directly for Fort Collins, Windsor, and Timnath lawns, instead of suggesting you try it yourself with a small home compressor.
Step four: plan for occasional watering after shutdown
Winterizing doesn’t mean ignoring your lawn until spring. Once the system is off, plan on occasional hand watering during extended dry periods without snow cover. CSU Extension’s fall and winter watering fact sheet puts that at about once or twice each month, and only when air and soil temperatures are above 40 degrees. The timing and conditions are in our post on dormant-season watering for Fort Collins lawns. Trees and shrubs near your lawn need their own watering plan too, which we cover in a separate post.
Why the order matters
Feeding the lawn while it’s still green means the nutrients actually get used instead of sitting there unused. Keeping your sprinklers running at normal settings until closer to the freeze, instead of shutting them off early, means that feeding and any late rain has time to soak in. Having your winter watering plan ready before the system goes quiet means you’re not scrambling with a hose in January. Shutting the system down too early, just to check a box, can leave your lawn and nearby trees short on water during weeks that are still warm enough to need it. Most of the trouble we see isn’t one step done wrong. It’s the order getting scrambled.
If you want help with the feeding or the sprinklers, we’re happy to get you on the schedule.
If you want help with the feeding or the sprinklers, we’re happy to get you on the schedule.
Clean Air Lawn Care Northern Colorado is owned by Dianne, Paul, and Luke DeLongchamps — a family business serving Fort Collins, Windsor, and Timnath with organic lawn treatments and solar-powered electric equipment.
