David M. Kopec, Extension Turfgrass Specialist
March is a good time to start fixing up uneven areas on your bentgrass greens. This means areas which need ‘local’ reseeding or surface cultivation of ‘course turf areas’ which have wide leaf blades from low shoot or plant densities. These are the areas that have regrown from small bare spots and now need to be ‘smoothed’ into the green.
Local reseeding:
For an area that is 40 square feet in area do the following.
1. Mix 1 quart of dry sand into a bucket.
2. Add 3-4 shot glasses (available at the clubhouse) of bentgrass seed.
3. Mix it up extremely well.
4. Sprinkle the seed onto the area.
5. Then, spike the green with a close tine metal garden rake. Spike the rake every 1-3 inches by walking backwards as you spike.
6. Spike in at least two directions.
7. Sweep in the sand/seed into the holes.
8. Add more sand only if necessary.
9. Hand water (and roll if possible).
You may pre-soak the seed if you wish, but it’s not necessary.
If you are using a spring pre-emergence (Bensulide or Regalstar) the seed will not come up. Hide a brand new 32 gallon green garbage pail close by. Have the crew water this area 2-3 times a day when they drive by. Identify the spot for them by dotting the center with green turf paint.
Cultivating small areas:
Areas with low shoot densities and coarse leaves need to be selectively topdressed.
1. Verticut lightly with close space narrow blades or spike with a very fine ‘garden weasel’ (garden roller/weeder with many narrow spikes). The ‘weasel’ will actually give you better control and less chance of damaging the bentgrass.
2. Hand topdress the area. Either shake sand between the hands, or sprinkle with a coffee can that has 1/8″ holes drilled on the bottom.
3. Brush in the sand. Repeat this every 7-10 days during good growing conditions. This will eliminate the uneven and grainy conditions of those small patches. If you need to increase growth on these patch areas only, throw a little 20-20-20 in the green garbage can.
Spring interseeding:
Interseeding with bentgrass seed in an effect to minimize Poa levels (return to bent) can be done in March. The Poa is starting to seed, but the germination of Poa in the spring is less than that of the fall (in the low desert elevations). The idea here is to introduce some bent into the canopy and hope that 20% of it will last through the summer when the Poa subsides. This can be done in two ways.
Option A: Aerification and Verticutting (best)
1. Aerify with 1/4″ hollow tines. Set the tines so they go 1/4″ underneath the green shoots. Aerify 2-3 directions. If you aerify to 3″, the seed at the bottom will not come up.
2. Verticut lightly in one direction only using close spacing and fine blades.
3. Seed the green at 2 lbs./1000 feet using a small rotary hand (monkey grinder) spreader.
4. Topdress and sweep.
Option B: Verticut only If play is too demanding follow steps 2, 3 and 4 above.
You will see bent coming up if you water once during the day. The trick is how to water the green when you are trying to ‘dry out’ the Poa as a stress transition technique. It ends up a judgement call.
Try reseeding bent again at the middle or end of May, once the Poa has flowered. This should assist in the long term conversion process.
Again, any pre-emergence applications in the spring will negate this process.