Sam Bauer, Extension Turfgrass Educator
HOT JULY, DRY AUGUST AND SEPTEMBER
A resounding sigh of relief was felt over much of the state as July passed. It was the second hottest July on record in Minnesota, and the hottest in 118 years of records throughout the rest of the country. Precipitation around the state varied greatly. From record droughts in northwest and parts of southern Minnesota, to record floods in the northeast, this summer was anything but typical. Homeowners in the Twin Cities metro should feel very fortunate to not be dealing with the after-effects in these areas. Still, if you were able to sustain the quality of your lawn throughout July, it was truly a blessing.
August came and went fairly quickly with very little love from Mother Nature, almost a three inch rainfall deficit in the Twin Cities. The map below from the MNDNR State Climatology Office puts precipitation deficits into perspective across the state from July 31st to September 24th.
September ended with only 0.3 inches of rainfall recorded in the Twin Cities. In fact, it was the second driest September on record. Central and northeastern Minnesota suffered the worst. What implications does this have on your fall lawn care practices? I'm glad you asked.
Fall is the preferred time for many important lawn care practices. From fertilization and weed control, to cultivation and seeding, there is absolutely no better time for cool-season turfgrass maintenance in the Midwest. But this year is different. The lack of precipitation in August and September has caused many of our Kentucky bluegrass, perennial ryegrass, or fine fescue lawns to brown out and cease growing, almost a revert back to summer dormancy for those homeowners that lack the availability of adequate irrigation. In order for your lawn to recover, you will need to begin irrigating regularly. This means more than just one or two cycles, but enough water to wet the root zone sufficiently to sustain turfgrass health.
AVOID PLACING ADDITIONAL STRESS ON DROUGHT-STRESSED LAWNS
Speaking of turfgrass health, if your lawn is stressed from lack of moisture, typical fall maintenance practices that we have recommended in the past will add additional stress. In this case, we might actually see our lawn quality decline from the practice, for example: aerating.
The best advice that I can give you is to determine the growing conditions that are furthest from optimum and correct those first. If your lawn is declining from a lack of moisture, irrigate. If you've been irrigating with little turfgrass response, soil compaction may be an issue, in which case aerating would help. Has your fertility program been adequate? Are there insect or weed pressures? These are all questions to consider.
Concentrate more this fall on creating the best possible growing environment for your turfgrass, and you will reap the benefits during next year's growing season. Adding turfgrass stress to an already stressful situation will do more harm than good.
TIPS FOR DROUGHT-STRESSED LAWNS
Return adequate soil moisture levels and turfgrass health before you conduct these practices.
• Aerate. While aeration is a great fall practice, it places stress on the turfgrass plant and may actually cause the lawn quality to decline.
• Dethatch or vertical mow. This process tears turfgrass leaves and crowns, and should only be conducted when the lawn is healthy.
• Spray herbicides. Systemic and contact herbicides used for weed control are more effective when weeds are actively growing.
• Fertilize with quick release nitrogen. High rates of quick release nitrogen fertilizers can have negative effects on drought-stressed turf. There is also a greater potential for environmental loss of nitrogen when the lawn is not actively growing.
• Mow too often or too low. Raising the mowing height and mowing less frequently will help encourage turfgrass recovery.
• Maintain soil moisture to promote turfgrass recovery.
• Spot seed and fertilize thin and weak areas with a high quality turfgrass seed mixture.
• Fertilize with slow release nitrogen sources and soil test to determine fertilizer requirements of phosphorus and potassium.
• Aerate when the lawns health has been restored.
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