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For optimum establishment, seeding should be done in late August or early September. Waiting as long as until Oct. can severely reduce establishment before winter, especially with the slower establishing Kentucky bluegrass. It is also important to seed early enough in fall to allow seedlings to mature to the point where they can withstand the stresses of winter. This was evident with perennial ryegrass seeded in Nov. 1990 which did not survive the winter. The soil temperatures were warm enough to allow germination in Nov., but the temperatures cooled too quickly to allow maturation of the ryegrass before winter. Do not seed when soil temperatures are warm enough for germination, but when there is not enough time left before winter for good establishment. It is be better to seed after soil temperatures cool so germination will not occur until the following spring. This is defined as dormant seeding and it is usually more effective than spring seeding and only slightly less effective than Sep. seeding. A possible problem with dormant seeding of quick-germinating species like perennial ryegrass is with unusually early spring warm spells, the seeds may germinate, only to die with ensuing cold temperatures. Therefore dormant seeding works much better from Bloomington and north because of colder winters. Turfgrass seeded at less than optimum times is often slow to fill in which allows many weeds to germinate and establish. This is especially problematic with Kentucky bluegrass. In our studies, Kentucky bluegrass seeded in May had over 3 times more weed infestation than Kentucky bluegrass seeded in Sep. Weed control in newly established turf is difficult because most herbicides are not labeled for use on turfgrass seedlings. An important consideration when seeding turf at non-optimum times and even optimum times of the year is that even though establishment is slow, the turf will eventually fill in. As long as the seeds or seedlings are not damaged, the grass plants will mature and gradually fill in. Even though Oct. 1 is one of the poorest times for seeding Kentucky bluegrass, plots of bluegrass seeded on this date in 1989 had 100% cover by the following August. The bluegrass seeded on this date was very slow to fill in and had substantial weed infestation, but eventually produced an acceptable turf. (Purdue University) |
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