As milder fall temperatures arrive in the coming weeks, some superintendents are going to be overseeding weak areas of bentgrass putting greens to regain turf cover before winter in hopes of returning to optimal playing conditions in the spring. If you have some areas targeted for seeding, it is important to consider the following factors.
Optimal Germination Temperature
Optimal creeping bentgrass germination temperature is 59 to 86 F. Oftentimes in the Upper Midwest, that ends up being around the second week of August through the end of September. Ensuring proper timing will optimize germination.
Seeding Method
Seeding can be done in a variety of ways, especially around cultural management practices like aeration that are often done in the fall. Remember that the size of the seed correlates to the depth it should be sowed. Bentgrass seeds sown in aerification holes several inches deep are not going to germinate as successfully as seeds located in the top half inch of the soil. Ensuring seed-to-soil contact is very important, and vertical mowing prior to seeding or lightly topdressing after is beneficial. Slit seeding is often the most effective way I see bentgrass seeded in my travels.
Fertility
New seedlings often benefit from some extra fertility. Many starter fertilizers can be used to help provide nutrition, particularly phosphorous and nitrogen. It is important to not overapply these nutrients. Excess nitrogen can injure new seedlings, and any fertilizer that goes unused by desired turf can increase weed pressure – particularly from winter annual weeds like Poa annua that can germinate later in the fall. A soil test can help determine how much phosphorus should be applied. Somewhere between 1 and 2 pounds of phosphate per 1,000 square feet is usually a good rate.
Seeding Rate
With approximately 6 million bentgrass seeds per pound, it is important not to overplant. An optimal seeding rate is somewhere between ½ to 1 pound of seeds per 1,000 square feet. It is not uncommon for superintendents to plant too many seeds in areas they are trying to recover. This can cause the seedling density to be too high and inhibit maturation, producing weakly rooted plants that are susceptible to disease and winter injury.
It has been a very difficult summer to maintain turf cover on putting greens, especially in poor growing environments. As efforts are made to establish new grass in weak areas, keep it simple and stick to the basics of establishment. It is important to do something to mend these areas, just try to avoid doing too much of a good thing.
Central Region Agronomists:
Zach Nicoludis, regional director, Central Region – znicoludis@usga.org
Tom Gould, agronomist – tgould@usga.org
Information on the USGA’s Course Consulting Service
Contact the Green Section Staff