Lawn Care Spring Update

Crabgrass
Facts, information and control

Crabgrass is a summer annual grassy weed. It actually grows in the late spring and summer while soil temperatures are consistently above 55 degrees. Being an annual grass, crabgrass lives for one season. It has very low nutrient requirements, and can basically grow anywhere; even in sidewalk cracks. Crabgrass is light green in color, coarse bladed and will root at the nodes when they touch the ground. A single crabgrass plant can produce up to 700 tillers. It is a bunch type grass, and a single bunch can produce up to 150,000 seeds during a season. This is why it can become such a large problem in lawns over just one summer season.

There are 2 main factors that affect control of crabgrass over the summer: The first is proper timing and application of a pre-emergent herbicide, and the second is turf density.

Crabgrass is a "cousin" to your turfgrass. It processes its food very similarly to the way your grass does. Because it is so similar to your turfgrass, the weed controls needed to kill crabgrass after it has already germinated and began growing in your lawn can easily damage your grass. For this reason, it is important to prevent as much crabgrass as possible from ever showing up in your lawn. This is accomplished by using a pre-emergent herbicide. A pre-emergent herbicide stops crabgrass before it can start producing seeds and rapidly spreading in your lawn. It is very important that the pre-emergent be applied early in the spring well before the temperatures increase. The common mistake most lawn owners make is starting too late in the spring.

Pre-emergent is the most effective way to control crabgrass in your lawn, but the pre-emergent will not work in a thin lawn nearly as well as in a lawn that has good density. So if your lawn is thin going into the summer, you should expect to have crabgrass even with the application of a pre-emergent in the spring. Bermuda and zoysia lawns have runners that spread into thin areas. Proper fertilization, good watering and mowing practices will allow these runners to spread more rapidly. Fescue grass does not spread like bermuda and zoysia, so any thin areas need to be re-seeded in the fall in order to increase fescue turf density. Another process necessary to increasing turf density is core aeration. It should be done every season to either relieve or prevent soil compaction. Core aeration should be done in the spring/early summer on bermuda and zoysia lawns, and it should be done in conjunction with seeding in the fall for fescue lawns.

More Crabgrass Images

Seeding Fescue in Spring
Good Idea? NO!

We are asked many times during the spring to provide estimates for doing core aeration and fescue seeding. After all, it seems that spring is a perfect time to seed the lawn: The temperatures are mild, the lawn and garden stores are putting fescue seed on sale, and everything is ready to start growing for a new season. The fact is we do not do core aeration and fescue seeding in the spring, and there are two main reasons why.

The temperatures are indeed very good for seed germination in the spring. The problem with seeding at this time of year lies with the increasing temperatures in the summer. In most cases, the new fescue gets excellent germination in the spring, and it seems as if it is developing quite well. But the root systems of the new grass are still very immature and underdeveloped when heat, drought and stress of summer sets in. Often times this new fescue that was looking so good in March is dead by June. Remember that fescue is a cool season grass; it grows and develops best in soil temperatures between 55 and 65 degrees, and it does not do well at all in Southeastern summer heat. If drought and heat stress does not kill the immature grass, brown patch fungus will.

The second reason we discourage seeding in the spring is probably the most important one. It has to do with the prevention of crabgrass and other spring weeds. Applying spring pre-emergent weed controls is our most effective means of controlling spring and summer weeds. We are unable to apply the spring pre-emergent weed controls if you have new grass seed down on your lawn because the pre-emergent weed control will severely inhibit the germination and development of the new seed. It is almost impossible to effectively control crabgrass and other annual weeds without a solid pre-emergent weed control barrier on the lawn being established in the Spring. In many cases the weeds will not only take over the newly seeded areas, but they will cause damage to the existing grass as well.

Spring Lawn Maintenance
The look of your lawn in the Summer is decided by how you care for in the Spring.

The goal of every homeowner with a lawn is to have it looking lush, green, thick and healthy during the summer. The problem is most homeowners do not realize they need to start the process early in the spring if they want to see the results in the summer.

Bermuda and zoysia lawns should be scalped in the spring after they start greening up. This is typically around mid March. Scalping entails removing the dead grass from last season. The lawn should be mowed to within 1/4" of the ground. Typically this involves mowing several times, lowering the mowing height as you go. All clippings should be bagged. If these cuttings are not bagged, the material will build up on the lawn and severely inhibit the ability of the grass to green up. If you do not have a mower that can be lowered to within 1/4", and if the mower does not have bagging capability, we strongly suggest you purchase one that does. The buildup of excess clippings on the lawn is called "thatch". Heavy thatch causes density problems, and it severely limits the effectiveness of the spring pre-emergent treatments. Remember that pre-emergent weed controls are the most effective way of controlling weeds in the lawn. You want to make sure that the thatch layer is less than 1/4" thick so it will not interfere with the establishment of a solid pre-emergent barrier.

 

 

Once the lawn has been scalped, it will be easy to see any ruts, low areas, or other depressions in the lawn. This is the time to apply sand to the low areas in order to smooth the surface of the lawn. Scalping is a good thing in the beginning of the season, but you do not want to have scalp marks in the lawn later in the summer. The only parts of a bermuda or zoysia grass plant that hold a significant amount of chlorophyll are the leaf blades at the top. The rest of the grass plant is brown in color. When the mower drops into one of these ruts or low areas, it causes the blade to remove all the green material from a section of the lawn. This leaves a half moon shaped brown scalp mark in the lawn. Sanding the low spots will eliminate unwanted scalp marks in the lawn later in the summer.

You should sharpen your mower blade after scalping the lawn. Mowing with a dull blade rips the grass blades and inhibits moisture retention. If your grass cannot retain moisture, it will not be able to stay green regardless of the amount of fertilizer we give it. After the lawn has fully greened up you should have it core aerated. Core aeration relieves soil compaction and increases the air, water, and nutrient uptake to the roots of your grass.