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Fall Lawn Renewal

Fall Lawn Renewal - by Carl Wilson

Lawns might have browned out in spots or thinned this summer. With cooler nights and shortening days, cool season bluegrass will tend to catch its “second wind” and recover. Lawns may also need some help - either routine renewal or a renovation.

Routine Renewal

Routine renewal might include some combination of spraying for weeds, core aeration and fertilization. Fall is one of the best times to spray perennial weeds such as thistle, dandelion, plantain, mallow and bindweed. Do make sure to spray actively growing weeds, not drought stressed ones. Many broadleaf herbicides are available to selectively take these weeds out of lawns and not harm the grass if label directions are followed. Total lawn spraying may be unnecessary if spot spraying will reach weed-infested areas.

Fall is also the most important time of year to fertilize lawns. Time the fertilizer application for October and no later than Thanksgiving. Apply the amount recommended on fertilizer product labels. If you have fertilizer left from spring or summer applications, use it. Your fall application doesn’t have to be a product marketed as a “winterizer.” Any lawn fertilizer will benefit root growth and encourage spring green-up next year. Fertilization promotes thick grass that resists weed invasion and is well worth the effort. Core aerate either before or after fertilizing.

core aeration holes

thin turf

Renovation (overseeding)

Lawns may need more than routine renewal if:

  • The lawn has thinned out from disease or irrigation coverage problems
  • The lawn has become shady over time from maturing trees causing thinning
  • The lawn was winterkilled especially in southwest exposures during a dry winter
  • The lawn is 40 or more years old and it is desirable to introduce newer, more durable bluegrass varieties

September is an ideal time to overseed bluegrass into existing lawns along the Front Range. Seeding after the first fall frost is not recommended. Have the lawn core aerated to “pull plugs.” You may even want to have the lawn aerated from two directions to make more than the usual number of holes.

Scatter seed across the lawn by hand or with an inexpensive handheld rotary spreader. The seed will drop into the aeration holes where it is more protected from sun and drying winds. Seed to soil contact is necessary for seed to germinate. A light top-dressing with peat or compost is unnecessary but can be done if desired.

The other essential follow-up step is to irrigate to maintain consistent moisture for 21 days to germinate bluegrass seed. Water frequently but for short times and DON’T saturate the soil. Often a minute or two applied 2 to 3 times daily is enough. If seed starts to germinate and dries out, it is killed.

Older, forty or fifty year old lawns can benefit from overseeding to introduce more durable, modern bluegrass varieties that will eventually spread and dominate. You also may want to try introducing bluegrass hybrids – crosses between Kentucky bluegrass and Texas bluegrass. Limited research at CSU suggests that hybrids have better than average drought resistance and excellent heat tolerance. They may be best in hot, full-sun lawn locations. The hybrids don’t look different than Kentucky bluegrass. They are commonly available from garden centers and include varieties such as Reveille, Longhorn, Thermal Blue, Solar Green, Dura Blue and Bandera.

See Renovating Home Lawns fact sheet for more information.

Photo credits: Carl Wilson
thin turf
core aeration holes

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Updated Saturday, September 25, 2010