Horticulture Principles and Practices

The seed should be free from weeds (especially noxious ones) as much as possible and
have a high germination percentage (at least 80 percent). If the germination percentage
is low, the seeding rate should be increased. Whenever possible, freshly harvested seed
should be purchased.
Time to Sow
The best time to sow grass seed differs from one region to another and is chosen strategically
to benefit from the weed cycle and adverse weather. Timely sowing ensures grass
establishment before weed seeds germinate or cold weather sets in. In the cool-season zone,
the best time to sow temperate grasses is late summer or early fall, which allows the lawn
to be established before freezing temperatures set in. Furthermore, when grasses are sown
in fall, the need to irrigate is reduced because of cooler temperatures and less evaporation.
In the warm-season zone of the South, a good strategy is to sow in early summer after clearing
away the weeds. Sometimes delays in construction projects may not allow the timely
sowing of seeds. The result is poor seed germination and thus poor lawn establishment.
Seeding Rate
Grass seeds are very tiny. Species such as bentgrass may have more than 10 million seeds
per kilogram (4.8 million seeds per pound). The objective of seeding is to obtain a quick
establishment and produce a dense lawn resembling a carpet. However, overseeding
leads to overcrowding and additional stress to plants, which consequently grow poorly
and delay the attainment of a quality lawn. Similarly, low plant populations delay the
covering of the ground, allowing weeds to infect the lawn. Sowing at the rate of 1 pound
per 1,000 square feet (0.45 kilograms per 90 square meters) will suffice for most grasses
that are sown in due season. Tall fescue and perennial ryegrass require much higher rates
of between 3 and 6 pounds per 1,000 square feet (1.35 and 2.7 kilograms per 90 square
meters). Seed companies indicate the recommended seeding rates on package labels.
Seeding
Small plots may be effectively seeded by hand, even though this method has the disadvantage
of uneven spreading. Mechanical seeders, which should be used for large areas,
distribute seed by one of three ways—drill, gravity feed, or broadcast. If a narrow strip is
to be seeded, using a drill may be most appropriate. However, drilling places seeds in narrow
strips, leaving wide bare spaces between them. Because ground covering is slow, weed
control is required during the establishment of a lawn. Gravity feeders may be manually
pushed or tractor operated. Similarly, broadcast spreaders may be portable or tractor
mounted. For very large areas, helicopters may be used to broadcast the seed. To reach
steep slopes, hydroseeding or hydromulching may be used. When one of these methods is
used, frequent watering is needed during lawn establishment. To increase the seeding efficiency
for uniform coverage, the recommended seeding rate may be divided into two so
that one-half is distributed in one direction on the first pass and the other spread crosswise
on the next pass (Figure 18–4). Mixing grass seed with sand in a mechanical spreader has
been found to aid in the even spreading of seed. Since grass seeds are so fine and lightweight,
sowing on windy days should be avoided. Furthermore, because they are so tiny,
grass seeds should not be seeded too deeply in the soil (less than 1 centimeter or 0.4 inch).
Proper depth of planting is accomplished by lightly raking the area after sowing.
Mulching and Firming
Mulching a freshly sown lawn has several purposes:
1. To protect grass seeds from predators (birds)
2. To prevent seeds from washing away during irrigation
3. To conserve moisture for germination
4. To control erosion of soil
18.3 Planting Turfgrass 551