Seed a lawn in mid-August? “Preposterous,” old-time gardeners would insist. “Best time of the year,” would be the reply of modern science.
Why are these two directly opposed opinions? Old-timers just took it for granted that grass seed planted in August would not grow—they were so certain that they never tried it.
They knew that common Kentucky bluegrass and the bents and fescues make their best growth during the cooler months of the year, and they felt that their seeds needed cool weather to grow.
Science Is Not Tied Down By Tradition
Science, however, is not tied down by tradition. For example, at Purdue University and other turf research centers, lawn specialists tried sowing grass seed every month of the growing season, from March to November.
Of these sowings, those made in mid-August produced the best turf in the shortest time.
Even grasses that sprout slowly, like common Kentucky bluegrass and Merion Kentucky bluegrass, showed well in seven to ten days.
The new seedlings made heavy top growth at first, but as the weather grew cooler, this top growth slowed up.
However, the roots then began developing rapidly and produced a solid mat by the time frost came.
Mid-August Sowings
Equally important was the fact that these mid-August sowings were not seriously invaded by weeds, as by that time of the year, the common annual weeds had all germinated.
Since the sun struck the ground at a sharper angle, it did not warm up the soil to the temperature that annual weeds require for germination.
No chemical sprays were needed to keep down broad-leaved weeds or crabgrass.
In contrast, spring-sown lawns are usually heavily infested before the young grass seedlings can compete and tolerate chemical sprays.
When we seed lawns in mid-August, we follow Nature’s pattern. In the wild, seeds of permanent grasses fall to the ground after ripening in late June or early July.
They do not sprout at once because they contain a natural inhibitor that keeps them from germinating until washed out by late summer rains.
If the seed were to sprout as soon as it fell, the young seedlings would have to compete with the older grasses when they are thick and heavy.
By germinating after the heat of summer has thinned out the older grasses, the seeds of the current year’s crop can grow without such severe competition.
Inhibitor
The inhibitor is water soluble and is gradually washed out of the seed by summer rains in the sections where most of our cool-weather grasses originate.
These summer rains come in late July and early August, so the seed is ready to grow at the end of this period.
Temperature
Another favorable factor in mid-August is temperature. Most grass seeds germinate best if the nights and days are cool.
In the seed laboratory, they are best tested at about 55° degrees Fahrenheit at night and 90° degrees Fahrenheit during the day.
Usually, late August nights provide conditions favorable to growth in the area north of the Ohio River.
Moisture
Moisture is another need. Autumn rains during the last half of August are usually favorable. However, even if rain does not fall, water applied by sprinklers does not evaporate as rapidly as it does earlier in the season.
Light
The third need is light. Grass seeds will sprout only if exposed to daylight. May, June, and July are light months; the sun is almost overhead.
This means that the seed on the soil’s surface dries out rapidly, even between frequent sprinklings.
In August, the sun strikes the earth at a sharper angle and does not dry out the surface moisture as rapidly. For this reason, the seed can be exposed to daylight without the danger of drying out if kept moist.
Soaking The Seed
Growth of the bluegrasses can be further speeded up by removing the natural inhibitor. This can be done by soaking the seed or watering the newly seeded lawn heavily.
Soak the bag containing the seed overnight in a pail of water. In the morning, take it to the sink and allow water to run through the seed. At first, the water will be brown. When it clears, the inhibitor will be gone.
Drain the seed and spread it on a flat surface in the sun for three or four hours. This will dry it enough to broadcast by hand or through a spreader. Plant at once.
Although the seeds of fescues and bents do not need this treatment, it won’t hurt them, so mixtures can be treated if they contain bluegrass seeds.
Mid-August planting does not do away with the need for ordinary care of the newly-seeded lawn. If the weather is unexpectedly dry, provision must be made for watering.
44659 by R. Milton Carleton