D.M. Kopec, Extension Turfgrass Specialist
Preparing for overseeding otherwise means managing the bermudagrass for accepting seed, without damaging the bermudagrass. Severely cultivated bermudagrass (verticutt) will result in poor transition next spring.
Over 75% of all golf courses will overseed early in order to meet club and play schedules. This is very rough on the bermuda, and the ryegrass, but you already know why. About 15% of all courses will overseed late, when the night temperatures are in the low 50°', which makes the soil cool quickly.
Greens and Tees:
Do not fertilize within two and one half weeks before overseeding. Use iron for color if you have to. RAISE the mowing height by 45%, and leave it there. Do this ten days before the overseed date. Roll (if you must) to maintain some ball speed. At two days before overseeding, stop mowing. On the day of final preparation, brush the greens to lift up the stolons. Then scalp down until you have vertical stolons with one or no leaves. This makes it easy for seed-to-soil contact. Then observe the surface. Verticutt lightly only to remove the leaves from the stolons. Do not rip into the thatch to expose very much soil or sand. Follow with seeding in two directions, then topdress with sand, roll, and water for emergence.
Fairways, Roughs, and Surrounds:
There is considerable difference in the amount of bermudagrass you must cultivate between Tifway (419), common, and most other seeded types. The same overall considerations exist as for greens. The difference is the magnitude of the operations, and what we do with the grass debris. You can either remove it, or use it as mulch.
In a nutshell, the following steps can be taken. At three weeks before overseeding, stop all nitrogen fertilization. At 12-14 days before overseeding, raise the height of cut by 50%. This causes the leaves to be less compact on the stems. One option is to apply PRIMO PGR to the bermudagrass. (If this is in your plan, raise the mowing height first.) Decrease the water applications by either skipping days, or applying lesser irrigation amounts by 25% (from days seven to four). If you like, DIQUAT or REWARD is still available for use as a desiccant to dry out and roll-up the leaves. Also, some superintendents have tried pelarogonic acid or SCYTHE to dry out the turf also. Follow application-timing windows according to the label.
At two days before dropping seed, remove 40% of the turf. You should now have a vertical stem with two - three side-leaves (common) or three - four side-leaves (Tifway 419). You can "mow down" lower again. This time you want to mow down until you have 1 to 1 ½ full side-leaves sticking out on each shoot. If the shoots are very dense (Tifway 419), you may still have to verticutt. Vertical mow to rip the leaves off the stems. Don't go overboard ripping stems out of the ground. Now, seed in two directions. Either drag mat, or follow by another mowing pass. This pass will provide mulch for the overseed. If you mow again, follow with the drag mat in several directions. Water for emergence.
After the overseed emerges, mow greens for the first time at 3/8" or slightly less with a sharp mower. This is critical for ryegrass. A walk-behind mower is better than a tri-plex for the first mow (when possible). Double mow down to 1/4", 3/16" and 5/32". It may take two weeks or more. If you scalp, try and remain at the existing height. The grass should "grow into" the new height. Avoid "ripping" the grass out of greens and tees by using dull reels. Aerify with ¼" solid tines and fertilize with quick release -N- from a three-way complete fertilizer.
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.