Just moved Grass is overrun with weeds

[irishmedic1]

I just moved to a house in S. Florida. ( zone 9/10) I have a small grass yard with St. Augustine grass. The lawn is overrun with crabgrass and broadleaf weeds. I am looking to get control of this lawn. Some questions.

1. As it is February do I start with a pre emergent herbacide and how often?
2. When do I use a fertilizer and how often?
3. How much time do I with between pre emergent herbacide and fertalizer?
4. As I have established crabgrass and weeds, do I also use a post emergent herbacide and how often?
5. How far apart can I use a pre and post emergent herbacide?
6. Can you give me some good brands of fertilizer and pre / post emergent herbacide.

Thank you

[Dchall_San_Antonio]

You may have crabgrass seed in the lawn but you cannot have actively growing crabgrass in Feb. It is a summer annual plant. If you post a picture of the weed we can ID it for you, but there's not much point to nailing it down. Why? Because the herbicide you will use toward the end of this month is going to take it out. The herbicide is atrazine. Most of the herbicide mfgrs carry a variety of it with some sort of purple label. Here's one variety.



Read the label 3x before using it. Don't get that stuff on you. Walk backwards when applying and apply with the wind to your back. It takes several weeks to see the results, but 'suddenly' you will notice you don't have any weeds...at all.

Here are some hints for growing good St Augustine. These may or may not address each of your questions.
Water deeply and infrequently. Deeply means 1 inch all at one time. Put out some cat food or tuna cans in the yard and time how long it takes your sprinklers to fill all the cans. Be sure to put some cans in spots that appear dry. The time it takes to fill your cans is your new watering time. Mine is 8 full hours using an oscillating sprinkler with my hoses and water pressure. An old neighbor had a high flow in ground system that filled his cans in 20 minutes. Your mileage will be somewhere in between. INFREQUENTLY means you won't water every day or even every other day. It means when the temps are in the 60s or below, you water ONCE PER MONTH. With temps in the 70s, water once every 3 weeks. With temps in the 80s, water every other week. With temps in the 90s, water every week - ONCE. Use this as a guideline to start. You will have plenty of humid, overcast days in the 80s which may allow you to extend the dry period. Take rain into account and watch the grass for signs of drying. I have gone as long as 6 weeks without watering following a Memorial Day downpour.

Mulch mow at the mower's highest setting - always. There is never any reason to lower the mower deck for St Augustine.

Fertilizer. If you are using chemical fertilizers, wait until early May to fertilize in So FL. The grass will come through the winter with some energy. If you fertilize too early, the grass will burn through that stored energy faster requiring fertilizer again in early May anyway. Just put it off. After the May application, you can fertilize again in September and again toward the end of the growing season. Do you have an end to the growing season or can you mow new grass all year long? I'm thinking of winterizing, which should be done only after the grass completely stops growing. If you use chemical fertilizer be sure to water it in immediately after application. The reason for that is to dilute the fertilizer before the dew hits it. I cannot recommend a good chemical fertilizer, because I stopped using chem ferts in 2002. I use only organic fertilizer now. When I started with organics i had many lawn issues. All of those got resolved with the use of organics, so I just continued using them. If you look at the ingredients in organic fertilizers, they usually start with a list of grains like soybean meal, alfalfa meal, corn meal, wheat flour, etc. If you visit your local feed store you can find these materials at about 1/6 the price of commercially bagged fertilizer, so that's what I've been doing. The application rate is 15 pounds per 1,000 square feet for most of those. Organic fertilizer can be applied any day of the year, or every day of the year, without fear of damaging anything. Cost per 1,000 square feet is slightly more with organics, but the complete lack of hassle has to be factored into the value. Well, there is one hassle with organics - they don't flow through a spreader like chemicals do. I scatter alfalfa pellets (rabbit chow) by hand for my relatively small yard. Use what you want. If you have questions about organics, I can help to read up on the organic lawn care forum here.

You can spray herbicide in late March in So FL. You may not need it again. If you see weeds in August, then spray again in mid September. St Aug is self sustaining once it becomes dense, so you should not need to use preemergents.

With the watering program outlined above you likely will not have fungal disease issues; however, Mother Nature can cause problems. If you get a disease that looks like this...

then please find some ordinary corn meal and apply at 15-20 pounds per 1,000 square feet. This is an organic approach which has been denied by several organiphobes, but it works for me for 16 years out of 16 years. Many others report it works very well especially for this disease in St Augustine.

If you happen to have crabgrass, there is a very specific solution for St Augustine and Centipede lawns. The solution is baking soda. Traditionally we have moistened the crabgrass with water and shampoo, because crabgrass is extremely hydrophobic. Wet the grass first and then dust the baking soda onto it through a very fine mesh. I use an old sock. Squeeze the sock and the dust falls out. Don't breathe the baking soda dust. After the water dries the crabgrass and surrounding St Aug should be white looking. The baking soda does kill the entire crabgrass plant and rather quickly. You should see it turning black the same day. The baking soda does not kill St Augustine, but it might slow it down slightly. Recently I read about a herbicide applicator on the end of a stick. Basically they use a sponge on a stick, dab the sponge into the herbicide, and dab it onto the weed. Supposedly this wipe-on approach works very well for hydrophobic plants like crabgrass. I don't get crabgrass, but I get dallisgrass, which is susceptible to baking soda, so I want to try this approach to minimize the trauma to surrounding St Augustine. I'm not sure how much baking soda I'll mix to make a solution, but it's dirt cheap, so we'll see.