Why is September "lawn month?"
As with other landscaping projects, timing is everything, especially when it comes to new lawns or lawn renovations.
There are only certain times of the year when you plant grass seed and nature helps ensure rapid germination and growth. Other times, grass seed just seems to lie there, or washes out, and you end up with poor results.
While success with grass seed is always related to adequate moisture, there are two seasons of the year in the northeastern United States when your odds for seeding success improve immensely: Spring and Fall. Since Spring is second best, we would like to focus on the Fall lawn seeding season. Let's narrow this down further to the month of September.
Why does September beat Spring?
WEEDS: Due to the growth cycle of weeds, Fall seeding faces far less weed competition, creating much better results.
2 COOL: Fall planted turfgrass has 2 cool, favorable growing seasons to become established before facing summer heat.
Those are the 2 reasons September is what I like to call "lawn month." These same principles also apply to rigorous lawn maintenance procedures, such as de-thatching and aeration. Since these two procedures qualify as "major lawn surgery" it's best to have ideal growing conditions for the lawn's "recovery period."
Why not seed during Summer?
Generally speaking, summer weather in the northeastern U.S. is not conducive to starting a new lawn, spot-seeding or doing any sort of renovation work on an old lawn.
HEAT: The sun is 'high in the sky' during summer, drying out soil and discouraging germination and establishment.
FUNGUS AMONGUS: Hot, humid nights create the perfect environment for many destructive lawn fungi, such as Pythium blight.
Those are the 2 reasons Summer is bad for seeding lawns. That being said, occasionally we experience cool, wet, rainy periods during the summer months when lawns will establish well. In those cases, it's still important to watch out for fungus problems during those hot, humid spells.
If you must seed in Summer, heed these DON'Ts....
DON'T water during evening hours, since this promotes a wet overnight environment that will encourage destructive fungi.
DON'T over-fertilize the new lawn, since lush, succulent growth is much more susceptible to disease problems.
Why not seed during winter?
A few old-timers told us they like to seed new lawns during winter months, since the freeze-thaw causes a 'honey comb' in the soil surface which create nooks and crannies for the grass seed to lodge. After all, grass seed will lay dormant until conditions are right for germination and growth.
However, working under this winter seeding premise, two downsides remain:
Finding a time when soil is dry enough to grade it, and..
The potential for losing soil and seed to erosion.
Summary: It's been our experience that the less opportunities you have for wash-outs and burn-outs, the better the outcome. Therefore, try to plant lawns during the season most conducive to fast establishment, and then do everything within your power to get the grass seed up and growing the first time around. No one likes watering for weeks on end and then having to do it all over again, so make your first effort count!