"Knee High by the Fourth"
Growing a Good Crop of Summer Golf
David M. Kopec, Extension Turfgrass Specialist
Remember the old saying that corn should be "knee high by the fourth"
(of July), if a farmer was going to have a good corn crop? Well luckily,
we don't have that in turf, but there are some benchmarks that you may
want to consider for your turf in July.
Hopefully, the overseed is finally going out quickly by the first two
weeks in July. Sometimes the Poa trivialis will last longer than
anticipated, but there are some techniques you can use to hasten the transition
of ryegrass and Poa trivialis. The first thing to do is to
take one or two cups out of the green and look for how much bermuda is
underneath the overseed. Pluck out the overseed. Then look for (a) bermudagrass
stolonsthe above ground runners and (b) rhizomesthe underground
runners. If at this time, you have many more rhizomes than stolons, then
you can induce a "gentle transition". If you have lots of stolons, you
can start a more "aggressive" transition.
Gentle Transition: (more rhizomes/few stolons)
The idea here is to maintain a good putting surface without a "loss
of turf" during a "sudden" or "forced" transition. The objective is to
force growth of the rhizomes to reach the surface, establish new roots,
and then make stolons.
1. Drop the moving height to promote stress on the remaining overseed
and expose the canopy to more light.
Aggressive Transition: (Lots of stolons present)
Groom to uplift the ryegrass crowns, and to cut the stolons on Poa trivialis.
Lightly verticut in one direction, and lightly topdress, roll, and fertilize
with 1 lb-N-/M
Decrease the irrigation two days after you have fertilized. Keep it on
the dry side, but don't damage the new bermudagrass plants. Keep it dry
enough so the overseed is stressed.
Fertilize each week with ¼ - ½ lb -N-/M from a highly soluble
source. Include P-K and iron as well. Water three days "normal", and four
days "dry"during the week..
Do not regularly verticut at this time, because you do not have lots of
stolons yet. Save your deep verticut (Tifgreen only) and aerification for
the second week in August.
Once you have 50-65% bermuda level, keep fertilizing and water to avoid
In this case, we want to increase the shoot density (stolons), so they
become independent from the mother plants. When this occurs, the green
becomes dense, as the shoots become vertical. This makes for a good bermudagrass
green, since it better approximates a table top from the vertical shoots,
rather than a green surface of long stringy stolons.
Fertilize the green with 1 lb-N-/M.
Drop the mowing height for one week to stress the remaining overseed grasses.
Water as usual.
Verticut moderately deep in one direction. This cuts, both the stolons
and rhizomes from the mother plant, and forces them to regrow on their
own and make "new" plants.
You may summer aerify now if wish also.
Add ¼ - lb-N-/M week for the next three weeks. Add P-K as well.
Provide adequate irrigation for maximum growth of bermudagrass.
Topdress the "new growth" accordingly so the new stolons from the new plants
re-root and grow up vertically.
Mid July is the beginning of the uphill summer stress period. For "Penncross"
greens, provide maybe 1/10th lb-N-/M month if needed. Substitute with iron
applications on a regular basis. Lightly topdress, early in the
morning or last thing at night, when necessary. On more aggressive and
denser varieties (A series, G series, SR1020, Crenshaw), you have to topdress
more often. If the bentgrass is very dense and spongy, then decide if a
deep groom or light verticut in one direction is possible (to open up the
canopy slightly). Then topdress lightly. In high traffic greens, this may
not be a problem, or it may not be possible to do at all. Tread carefully.
Some of the "summer aggressive" varieties will actively grow when fed nitrogen,
but this can cause real problems. Start with the regular iron application
programs to maintain color.
High traffic spots will start to show thinning at this time. Move pins
accordingly and promote exit schemes with the golf professional so he can
pass those on to the players. Clean up passes from the tri-plexes are a
summer bummer. Either aerify with ¼" solid tines, or use water injection
aerification. You don't have to do the entire green. If possible, make
the clean up pass with a walk-behind mower, two passes wide, while still
mowing the green with the tri-plex. This is a good compromise.
Persistent dry spots are either from poor irrigation, or from localized
dry spots (soil condition). You can apply a wetting agent selectively with
a hand pump sprayer on chronic problem acres, and aerify just these spots
as well. There is no substitute for proper hand watering.
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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.
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