David M. Kopec, Extension Turfgrass Specialist
Bermudagrass is most likely the toughest grass used for turf in areas of the desert southwest, the southern plains, and the humid southeastern United States. No other warm season grass has so many attributes. These include:
· excellent resistance to heat and drought
· low water use rate
· dense sod formation
· tolerance of a wide range of soil pH ranges
· good tolerance to salty water and conditions
· good traffic tolerance
· relative ease of establishment
· grows on hard soil surfaces and shallow soils, better than most other grasses
Because bermudagrass has specialized growth stems and a relatively rapid growth rate, it is usually excellent at crowding out weeds. Also, this is the primary reason why bermuda grows back so well when it is injured. Underground shoots (called rhizomes) help bermudagrass fill in void spots in a lawn. Above ground runners (stolons), similar to those on strawberry plants also serve the same function. While these properties are highly beneficial, they are often disdained as making bermudagrass and "invasive weed" where it is not wanted. Where did bermudagrass come from anyway?
Like almost all of our turfgrass species, bermudagrass is an introduced plant to the United States. The origin of the first introduction of bermudagrass most likely came from contaminated hay, which was used as bedding, when slaves were brought to America. Millions and millions of seeds were distributed initially across the eastern United States. Surviving plants then were able to make more seeds and so on.
Bermudagrass plants were then used exclusively for forage purposes for hundreds of years and no doubt also as a lawn grass by default, even though seed was sold mostly for forage. Bermudagrass was used in the southern United States in the early 1900's as a golf course turf, and was used as an "alternative" for sand greens, which were exactly that – a putting surface comprised of sand, with no grass! Over time (many decades), lower growing types of "common bermudagrass" began to show up on seeded bermudagrass greens. Greenskeepers and only a few scientists treated these findings with curiosity. In the 1940's, one such plant was collected from a golf course in Savannah, Georgia. After further testing and evaluation, it was released as a single plant (sod-type) bermuda named "U-3." In the mid-1940's, Dr. Glenn Burton of the USDA in Tifton, Georgia asked golf course superintendents in the south to send him plugs of bermudagrass "from the best part of their best green. These plants were increased in number so they could be evaluated for turf performance, winter survival, and ability to grow back in the spring after they were overseeded with annual ryegrass in the fall. One of the superior plants from this collection was crossed with a disease resistant pasture type bermuda. One of the plants that originated from that cross was later released in 1952 as "Tifflawn" bermudagrass. This again, was a single plant variety, and was sold as sod. Dr. Burton also discovered that other species of bermudagrass produced low growing plants, which may have turfgrass potential. One of these species was African bermudagrass. Plants of African bermudagrass are low growing, but tend to scalp in the heat of summer temperatures. It is closely related enough to common bermudagrass that it will occasionally cross with common bermudagrass and make a first generation plant. However, this plant is a sterile "mule" which will never make viable pollen or seed ever. Dr. Burton capitalized on this discovery and made many crosses between low growing African and better common bermuda plant selections. After years of testing hundreds of sterile hybrid mule plants for turf qualities, several "hybrids" were released from the Tifton Experiment Station in Georgia. These included "Tiffine" (an improved lawn type) and Tifgreen, the first major improvement in bermudagrass for greens and other closely mowed turfs. Tifgreen was released in 1956 and is still sold and in use today. Many golf courses in Arizona are planted to Tifgreen 328 bermuda. It is not for home lawn use because it requires low mowing heights of ½" or less. It's predominate use is on greens mowed at 5/32" (certainly not within the management level of the average homeowner).
In 1960, another sterile vegetative (mule) hybrid was released called Tifway 419. Just like Tifgreen, Tifway 419 had finer leaves and more surface shoots than common bermudagrass, but it grew taller. Tifway is a popular hybrid bermudagrass used in Arizona. It is best looking when mowed with a reel-type mower at base height ranges of 1/2 - 1.0 inches. Although it can be mowed taller with a rotary mower at heights of 1/2 – 2.0 inches, it often becomes leggy and tends to show scalping injury symptoms during the summer monsoon.
Other vegetatively propagated sterile hybrid bermudagrasses include Tifdwarf and Tifway II. Tifdwarf is used for golf course greens only, while the same applications for Tifway II applies to Tifway.
Tifdwarf was released in 1965 and Tifway II was released in 1981. Since then, seed companies and other universities have commercially released many other improved seeded and sterile "mule" vegetative bermudagrass varieties.
Remember: Any bermudagrass can be increased and sold from vegetative propagation means (sod, plugs, stolons, etc.) It does not have to be sterile. But, all sterile hybrid bermudagrass varieties must be established by vegetative propagation methods.
A quick note to remember – if you buy bermuda from seed, it will make seed. If it makes seed, it will make pollen.
The conversation often arises in Arizona regarding "hard and soft water," and how this affects irrigation. A common misconception is that "hard water" is bad for irrigating lawns and shrubs. Therefore, I need to have a "water softener" installed.
Well, there are really two and perhaps three things to think about here:
1. Perhaps, the homeowner may actually first be confusing water and/or soil salinity with hard water.
2. What is hard water?
3. What is soft water?
This issue deals with water salinity. Next month's issue will address "hard" and "soft" water, which are very different. Soil and water salinity will stress plants, both turf, and any irrigated trees and shrubs.
Water quality tests from an agricultural lab will test a water sample for salt levels. Salts in the water change the chemical properties of the water. Basically, salts (when dissolved in the water) compete with water itself, to behave as pure water. Turfgrass and landscape plants find it very easy to take up pure water. This is because pure water is not "distracted" by the salts.
If salt levels increase in irrigation water (either domestic or non-domestic water), it becomes harder for lawns and landscape plants to "take-up water," even though the soil is moist. Therefore, salty water actually requires more of the same salty water to keep the lawn and shrubs alive! Consequently, the more salty the water, the more often you need to irrigate.
Also in this case, you can apply more water than the grass needs. This causes leaching, with is very necessary. Leaching washes away the salts in the soil, with newer, "fresh" water, even if it is the same salty water you are using all along.
These practices cause the necessary leaching of salts - - away from the turfgrass roots. The result is the constant prevention of salt build-up in the SOIL, which itself is the determining factor on lawn and shrub performance.
In lawns that have poor drainage, salts can build up over time, even though salt levels in the water may be "low" or "medium." This is because the salts have nowhere to go! The salts move with the water, thanks to gravity. If any layering occurs in the soil, and different strata occur, drainage will be inhibited. That's why 2.0 inches of "soil" dumped on top of a "rock-hard" soil can eventually lead to a salt problem. That's why a hard-pan of caliche 3.0 inches below the turf soil impedes drainage, and a potential soil salt problem may be caused over time.
Homeowners often see white salt crusts on the soil at the edge of the lawn, or around the edge of plant berms. And yet, the plants or shrubs are not showing any stress, and look completely normal. The "surface salt" that you see here are salts that are evaporating along the edge of the soil, that was NOT ACTUALLY IRRIGATED. In these spots, the water has evaporated from the soil surface, which leaves the salts behind. You don't see salts close to the shrubs, or within the lawn itself, because the water has moved down in the soil, and this also minimizes evaporation at the surface.
Solutions to using saline water
In all practicality for homeowners, the water salt load is rarely critical – because you're using "drinking water." Almost all lawns and shrubs can tolerate our "drinking water" in Arizona. For people who manage large turf acreages (golf courses, parks, etc.), other water sources may be used. Water salinity may be much different (greater) from these sources than domestic water. If salt crystals appear within the middle of the lawn, you need to apply more [of the same water source] to wash the salts down.
To help increase the downward movement of water, it is best to poke holes in the lawn, using a power driven aerifier. These machines poke holes 2-3 inches in the ground. You should leave the holes open. The grass will actually fill in the holes. Don't be tempted to, or feel that you must "fill in" the holes with sand. Rake up the soil cores, or grind them up in place with a rotary mower. The open holes are more important to have to keep the salt levels tolerable.
Bermudagrass is quite salt tolerant. Tall fescue and ryegrass are moderately salt tolerant. Kentucky bluegrass is less salt tolerant than the above. Remember that salt stress causes the turf to look like it needs water! The grass will be dark blue-green in color, it will start to "wilt" and "curl" even though the soil is moist (screw driver goes in easily).
If your lawn suffers from salt stress, you can also help the lawn by mowing the turf at a higher mowing height that it is set for currently. This is not a problem for common bermudagrass, E-Z Turf, Midiron bermuda, or 99% of the improved seeded lawn type bermudagrass varieties, tall fescue, perennial ryegrass, and most lawn type Kentucky luegrass. Raising the height on Tifway (419) bermudagrass above 1-1/2 inches can often result in a scalped lawn, even if you mow three times/week. This is because most of the leaves will "migrate" to the end of the upright stems. When you mow off the tips of the stems, you can actually remove a lot of the leaves – because they are located at the tips of the stems. They exist at the tip, because of the unusually higher mowing height. Normally, when Tifway (419) Bermuda is mowed at ¾", three times per week with a sharp reel-type mower, the stems grow along the ground. The leaves are more evenly spaced across the entire length of the stem. So, less scalping occurs on Tifway when it gets mowed regularly at 3/4" or less.
Always remember, scalping a lawn is bad. Scalping a lawn that has salt stress is very bad.
To figure out how much salt is in your irrigation water, contact your local County Extension Office. They will give you an address for labs that will test samples.
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.