You may think of the summer as being the time for watering the grass, but do not think that you can stop watering your lawn in the fall. Southerners will be reminded by the heat of the ongoing need for irrigation, but even Northerners are not off the hook. Along with mowing the grass at the right height, fertilizing it correctly, and the timely removal of those pesky fallen leaves, proper watering is one of the critical aspects of fall lawn care.
When to Stop Watering the Lawn in Fall
You should not completely stop watering your lawn in fall until the ground freezes. After the ground freezes, it would be pointless to water your grass, since the frozen ground would act as a barrier, blocking the water's path to the root zone.
This is why the cold temperatures of northern winters are said to create desert conditions. "Desert" may conjure up images of cacti and succulents growing in hot sands, but it also applies to regions in which water is locked up in the form of ice. When the ground freezes, water becomes inaccessible to the roots of plants, regardless of how much snow lies on top of the soil. Their way of combating such desert conditions is called "dormancy": They enter a sleep-like state in which they do not need water.
Why Watering Lawns Is Important Throughout the Fall
While it is a good idea to keep the soil under your grass moist right through late fall, it is even more important for Northerners to resist the temptation to stop watering the lawn in early fall just because the temperature has cooled off. If the type of grass that you have is a cool-season grass, then this period of time, by definition, is a period of strong growth for your lawn.
Do not deprive it of irrigation during this critical time. An adequate water supply for grass roots is essential for proper nutrient uptake during growth periods. And if your lawn is not absorbing nutrients sufficiently, it will not achieve optimal health.
Your grass does keep growing for a good part of the autumn even when you are not aware of it because the growth is occurring only underground in the root system (where you can't see it). More specifically, there is growth activity taking place in the stolons of your grass. Such underground parts of your grass plants form their "foundation," if you will. The activity going on at the stolon level is important to the long-term health of your grass, helping it repair a summertime's worth of damage and getting it ready for the year ahead.
Keeping a Delicate Balance
As important as it is to water your lawn in fall until the ground freezes, it is just as important not to overwater it, either. If your area receives sufficient rainfall in autumn (one inch per week), you may only have to water lawn areas that have been overseeded or where new lawns have just been started. Overwatering can harm the root system of grass and furnishes an open invitation for fungus to invade your lawn. Fungal diseases thrive in areas with excessive moisture.
Grass in lawn areas is more vulnerable to the spread of fungal diseases than most plants in your landscape are. A lawn is made up of countless individual grass plants packed tightly together. A fungus on one such grass plant is bound to spread to its neighbors. Think of a lawn as potentially being a highway for fungal infestations. This is why avoiding overwatering is so important.
But relatively warm, dry spells occasionally occur throughout autumn, especially in the South. Remember to water the lawn during these spells as you would during the summer.
The time of day that you water the grass is also important: Watering it in the early morning is best because then the grass has all day to dry out before night falls. For the same reason, the evening is the worst time to water your lawn. In this respect, watering your lawn in the fall is no different from watering your lawn in the summer. This is one reason why automatic irrigation systems come in so handy: They have timers that you can set so that you do not have to be an early riser to get the grass watered in the early morning.