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Henbit

Spring lawn care

By John Fulton

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[April 10, 2014]  Lawns are really greening up with a little moisture and some warmer temperatures. While we have passed the recommended date for seeding, there are many other areas of lawn care that should be on your radar.

Fertilizer is always an area of many questions. The place to start is a soil test. This will tell you where you are starting from. Basic soil test levels for phosphorus, potassium and soil pH should be in the neighborhood of 40, 350 and 6.1, respectively. These numbers will provide a great environment for grass. Phosphorus and potassium are on a pound-per-acre basis. This must be considered if you use labs that report in parts per million, which will give numbers half as large. Grass will really grow in very poor conditions, but it certainly won't have that manicured lawn look many strive for.

Lacking a soil test, or being at recommended fertility levels, general maintenance applications provide a pound each of nitrogen, phosphorus and potassium per 1,000 square feet of lawn area in May and again in September. Really lush lawns will usually have twice as much nitrogen applied in a season, but split among four applications.

If you decide to try late seeding this spring, remember a couple of things related to weed killers. First, you can't use crabgrass preventer in the spring if you put down seed. The crabgrass preventer doesn't know the difference between grass seed and weed seeds. The second rule is to mow the new seeding at least three times before trying any broadleaf weed killer. Generally this means spring broadleaf control doesn't happen when you seed in the spring. The end result is if you seed in the spring, you control weeds in the fall. Seed in the fall, and you control weeds and crabgrass in the spring.

If you do plan to use a crabgrass preventer, time it so it is on about when the forsythia blooms. That is assuming it actually blooms this year. Many of the flower buds were cold-damaged in the winter we just went through. This would be the approximate soil and air temperature needed for the crabgrass to germinate. About now is a good guess, but the date can vary widely with the weather. Many crabgrass preventers also only last for four to eight weeks, so plan on repeating the application in June anyway.

If you have missed some early germinating crabgrass, you can try one of the post-emergence chemicals  put on the actual crabgrass when it is small  such as DSMA or MSMA. They may temporarily discolor lawns, and all the statements about new seedings apply to these as well.

One last item for the week. Many lawns have brown spots or patches. In most cases these are a warm-season perennial grass such as nimblewill. There is no selective control for these grasses, meaning glyphosate (Roundup). These spots green up slowly and brown out early. The best plan is to spray them in late July when they are growing, then put down new seed in mid-August.

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Early spring lawn weed control

Each year, the winter annual weeds chickweed and henbit run No. 1 and 2 in the early spring as lawn and garden weeds. Winter annual weeds can actually germinate in the fall, carry through the winter, then get going very early in the spring. They also are done by the heat of the summer, leaving seed to germinate again later in the fall.

Right now chickweed stands out in yards because it is quite abundant and has a lighter green color than grass and most other weeds. It is even evident as grass is just beginning to green up. There are two types: common chickweed and mouse-ear chickweed. Henbit is easier to identify since it has purple flowers and smells like mint. It is very noticeable right now.


Chickweed

The straight 2,4-D that is used on dandelions seems to act like a fertilizer for chickweed and other problem weeds. The 2-4D is a growth regulator, and if it doesn't actually kill a weed, it does make it grow faster. Combinations that contain 2,4-D, MCPP and dicamba are rated very effective on chickweed, henbit, red sorrel, purslane, white clover and others. These combinations are sold under several different trade names. You can find these at most hardware, discount, and lawn and garden stores. Just check the label under active ingredients and check for two long chemical names and dicamba. You can also check to see that it says it will control chickweed and henbit.

This group of chemicals is effective in the 50-degree range and up. It just takes a lot longer for control with very cool temperatures. Remember that the control time for most broadleaf weeds is early May. As with any chemical control, read and follow label instructions very carefully. On these product labels there will be some cautions that you should be aware of concerning injury to sensitive plants. This is because dicamba can drift as a vapor for a few weeks after you apply it if the weather gets hot and sunny.

[By JOHN FULTON, University of Illinois Extension director for Logan, Menard and Sangamon counties]

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