Road Hole Shorts

Golf Design, golf, golf, GOLF

Guest commentary: Warm versus cool – which do you prefer?

By Mary Armstrong/For the Sun-News
Posted: 05/13/2011 01:28:18 PM MDT


We are fortunate here in Las Cruces to have golf courses that have cool season
grasses and golf courses that have warm season grasses. If you haven’t noticed,
NMSU and Las Cruces Country Club have predominantly warm season grasses (cool
season greens), while Picacho Hills, Sonoma (except much of their roughs which
are a warm season native grass) and the new Las Cruces Course have cool season
grasses. You might notice that the two oldest courses in town have predominantly
warm season grasses, while the newest courses have cool season.

First let’s explore the differences between grasses. What does warm season
and cool season grass really mean? Well, they really are literally defined. A
warm season grass is one that thrives in the summer heat. In our area, they
begin to green up in April or May, but don’t really begin to show much growth
until we get into the heat of June. Throughout the summer, bermudagrass fairways
offer perhaps the best ball-striking surface I’ve ever experienced. In our
cooler months, bermudagrass and most other warm season grasses become dormant,
thus the straw color. Mostly we see bermudagrass – common bermudagrass and
cultivars. There are some courses in other locations that use zoysia for
fairways, and we are seeing a greater use of native grasses such as buffalograss
in roughs.

On the other hand, cool season grasses don’t tolerate extreme heat or cold
well and their vigorous growth periods are typically in our “shoulder” seasons –
spring and fall into early winter. Cool season grasses really don’t ever become fully dormant in
our climate or if they do it is very brief. They do take some pretty hard hits
from frost and traffic on turf that frost on it. Some cool season grasses that
are used on golf courses in the area are bentgrasses on all greens in the area
and bluegrass, ryegrass and some fescues on all other areas of courses – often
in custom mixes. Agronomically speaking, cool season grasses generally germinate
quickly and warm season grasses are a little slower and therefore slightly more
difficult to establish. Both warm and cool season grasses are subject to insect
pests and disease although cool season grasses usually require slightly more
intensive management.

Aesthetically, I believe cool season grasses have it over warm season grasses
– no contest – especially when the large number of cool season species and
cultivars are selected for their vivid contrasts in color and texture. Since
bermudagrass and its comparatively small number of cultivars are basically the
only choices for warm season applications, the range of color and texture
choices is small. If there is a golf aesthetic that I miss from back-east it’s
the sublime contrast of a fine bentgrass fairway against the dark green of a
bluegrass – ryegrass rough.

Water usage is often identified as a key reason to select warm season grasses
– especially in our locale. While it is true that bermudagrass is more drought
tolerant than many cool season grasses, there are cool season grasses available
for selection that have some drought resistance. Drought tolerance is determined
by the ability of the plant to resume growth after water has been completely
withheld for a given period. Bermudagrass can go without water for a period of
time and then become revitalized when irrigation is resumed. Very few if any
cool season grasses can do this. Ordinarily a cool season grass that is without
water for more than a week during the summer will be dead. This makes cool
season grasses more susceptible to catastrophic failure – when your favorite
course becomes toast!

Bermudagrass also has it over most cool season grasses in water usage. It is
dormant for five or more months of the year and requires little or no water
during that time. Cool season grasses have a shorter dormancy period locally,
but the real kicker is that on any given day, cool season grasses require 30 to
50 percent more water. So it seems that for our area, warm season grasses would
be the turf of choice. Not so fast bucko; the problem with bermudagrass is that
when it is dormant its playing characteristics diminish and much of the
aesthetic attraction typical of a golf course is lost. Why else would courses
overseed into dormant bermudagrass? This is especially true of courses that hope
to attract golfers from the north in the winter. The snowbirds thirst for their
golf fix and a straw colored canvas with seemingly “dead” turf isn’t going to
quench that thirst.

So, is overseeding into dormant bermudagrass the answer? It may seem so, but
overseeding is expensive – as much as 50,000 – 100,000 dollars for the fairways
of a typical 18 hole course. This of course means water usage will go up
significantly since the ryegrass or Poa trivialis that is often used requires
irrigation – as any actively growing grass would. Then there is the problem of
getting rid of the overseeded grass once the summer arrives. Contrary to popular
belief, overseeded grasses don’t simply “die-out” when the bermudagrass starts
growing. In places where warm season grasses are weak – areas of shade or heavy
traffic – the ryegrass will persist. If you look at any course that has
bermudagrass in our area, you will see areas of green grass throughout the
winter each year. Bermudagrass doesn’t do well in these areas and so the
ryegrass has persisted and further weakened the bermudagrass. What’s more,
continuous annual overseeding (at least in our area) weakens the bermudagrass
stand because the rye “holds on” long enough to reduce the already short three
to four month bermudagrass active growing season. For those courses that insist
on overseeding, a chemical eradication of the overseeded species is necessary at
a cost of between $5,000 and $10,000.

Taking note that the newer courses in our area are all cool season grasses
would seem to suggest that the selection of warm season turf is outdated. This
isn’t necessarily the case. Because we are in the transition zone, there are
some years that cool season grasses perform best and other years that warm
season grasses do better. Then there are those seasons where both can do well
and the very worst of years where both are a challenge to maintain. You might
also note that just a little further south in El Paso, nearly all courses have
bermudagrass, whereas a little further north cool season grasses are clearly the
choice. Our “normal” year probably favors cool season grasses, especially with
an adequately designed irrigation system and water supply. But it’s a
complicated problem. Let’s hope the future holds breeding and selection that
makes warms season grasses more attractive and cool season grasses requiring
less water.

A golf architect in New Hampshire for over 20 years, Armstrong brought her
craft to Las Cruces in January 2010. She is the founder of Armstrong Golf
Architects, which provides planning, designing, permitting and construction
monitoring services for golf course projects. You can comment on her writing and
view past articles at her blog: https://roadholeshorts17.wordpress.com/.

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