you still can use pre-em. Lesco 0-0-7 from Home depot will still control some weeds. If you want a decent looking st augustine lawn... You must mow them at 4 inches height. They do much better in shady area at that height. You must fertilize to thicken them up. You must water deeply and infrequently. Since you have pecan tree, I would say 2 inches worth of water every 2 weeks. That's 1200 gallons of water per 1000 sqft. It must be slow soaking type so the ground can absorb all the water without water running off. That will saturate 12 inches of soil where all the roots are. What it looked like before... Anyway, if you water all the time like 3 times a week for only a few minutes, you will promote a ton of weed growth but not grass or trees. They have shallow root system so they like frequent watering. The weed seeds need frequent watering to germinate and grow. When you mow high, it prevent sunlight to the ground for weed seeds to germinate as well. Tall grasses in shade will absorb more sunlight and perform better. Also it promote deeper root system so it cuts down frequent of watering. I've seen my st augustine grow 16 inches of roots... I usually water every 2 weeks. I tend to get lazy at times with manual watering but they turn out fine. It proves that st augustine is not water consuming as everybody claimed to be. I just don't think they have proper knowledge on how to maintain st augustine the right way. Actually, bermuda and st augustine require same amount of water to look good. In my opinion, it's a lot easier to garden with st augustine and maintain st augustine than bermuda ... I use organic fertilizer like soybean meal from feed store. No weed control of any kind. I water deeply every 2 weeks.

I found this place just 30 minutes from me: TurfGrass America. The lady there said that this would work best for our area: http://www.turfgrassamerica.com/iProduct.aspx?ProdID=126 St. Augustine Del Mar , description at the bottom of this note. It says vigorous, I'll have to find out what that means exactly. $170 for a pallet...which if it can do every 5 feet would be enough I think. I'm on a 2 year schedule so I know it'll eventually get there. Yes, it is a big lawn and I am worried about the water. I'm considering either rainwater collection and/or reverse osmosis from a nearby creek! St. Augustine DelMar® Stenotaphrum secundatum DelMar® St. Sugustine DelMar® St. Augustine is a vigorous, dark emerald green, medium-coarse textured lawn grass. It is one of the most cold tolerant varieties of St. Augustine making it a great choice in colder climates such as Dallas/Ft. Worth, and has very good shade tolerance. It also grows well in full sun. DelMar® turns golden brown in its dormancy. DelMar® tests at the top of National testing in overall quality among St. Augustines. DelMar® is the highest ranking cold tolerant, St. Augustine Decline Disease Free St. Augustine grass available. DelMar® St. Augustine is a vigorous, dark emerald green, medium-coarse textured lawn grass. It is one of the most cold tolerant varieties of St. Augustine making it a great choice in colder climates such as Dallas/Ft. Worth, and has very good shade tolerance. It also grows well in full sun. DelMar® turns golden brown in its dormancy. DelMar® tests at the top of National testing in overall quality among St. Augustines. DelMar® is the highest ranking cold tolerant, St. Augustine Decline Disease Free St. Augustine grass available. Area: 1, 2, 3, & 4 Intended Use: Residential & Commercial Availability: Sod Mowing Height: 3" Optimum

What I would do is to fertilize only the St Augustine. Mow at the highest setting and allow the St Aug to go 2 weeks. Water deep and infrequent like we talk about and "favor" the St Aug. Your grass in the shade will need water less often than the grass out in the full sun. Don't water when the crabgrass looks dry. Water when the St Aug out in the sun looks dry. The shady grass will appreciate it, and it still won't encourage weeds. Crabgrass is a summer annual plant that thrives in the heat and full sun. With your lot size it's going to take a year or so for the St Augustine to completely grow out and take over. If you wanted to speed up that process, put a couple pieces of St Aug sod around amongst the weeds and do the 1,2,3 above. As the runners spread out, you have to fertilize along the runners, too. I use organics to fertilize so I'm not at all worried about over applying fertilizer. If you have access to the Floratam variety of St Augustine, use that out in the sun. If you want to use a spray weed killer, you cannot use normal Weed-B-Gone with 2,4-d in it. You have to use atrazine. Everything else seems to kill St Augustine. Here's one you can get at Walmart. Read the directions carefully. This stuff is not to be trifled with. You have to walk backwards as you spray so you don't walk through the wet grass. That makes planning your route slightly more important. Don't paint yourself into a corner where you can't get out. And you can only spray it twice in a year, so choose your timing wisely. Remember you are only wetting the weeds, not drenching the soil with it. It can take 2 weeks before you see the first signs of the weeds dieing, but "suddenly" they'll all be dieing. All you need to spray is around the St Augustine runners. I would leave the rest of the weeds to grow until the St Augustine spreads to fill it all in. When you spray around the runners, that kills the weeds around the runners giving them more light and soil to expand into. And you don't need to spray in the middle of the dense St Augustine except where you have the clovery stuff growing. Once it gets pretty dense it fights off the weeds by itself. Also rather than connecting a bottle like that directly to a hose I connect through another nozzle with a valve so I can turn the flow on and off. Those are cheap at Home Depot or Lowe's. Here's a link to a picture. Cheap hose-end valve.

Good point about the shade. Can you post a mid day picture taken from, say, across the street, showing how much shade you get? Generally St Augustine will spread about 2 inches per week when the temps are in the 70s if everything is going well. You applied a chemical fertilizer waaaaaay too early even for the Woodlands. I just read Randy Lemmon's website recommendations. At first it sounded fine, but he gets into preventive treatments for disease, which I STRONGLY disagree with. Your soil requires a healthy population of beneficial fungi to be healthy. Treating it for no reason kills off the beneficial fungi and destroys the soil biology. Then looking at the rest of his suggestions it appears he's selling fertilizers just like Trugreen is. He's just not applying it for you. And he's selling far too much. Growing great St Augustine is really easy. Water deeply (1 inch all at one time) but infrequently, mulch mow at the mower's highest setting every 1-2-3 weeks (depending on how fast it's growing, fertilize once in early May (for the Woodlands) and again on Labor Day and Thanksgiving. You do not need to core aerate. As you pointed out it's hard work. You can do a much better job by spraying the lawn with shampoo at a rate of 3 ounces per 1,000 square feet followed by deep watering. Then 3 weeks later you can reapply if you think the soil has not become soft enough. I sprayed mine in 2012 and after a rain like today it's almost too soft to walk on without turning your ankle. If you want to get rid of weeds, wait until April and spot spray the weeds with an atrazine product. Be careful to read the directions 2 times. You should only spray atrazine once a year so make it count. It will kill just about everything except the St Augustine in 3 weeks. The odd thing about spraying it is you have to walk backwards so you don't walk through the stuff you sprayed. Atrazine is not a friendly chemical, hence these warnings. After a decade or so of doing these lawn care forums I'm willing to go out on a limb and proclaim that most people do not water properly. I mentioned deep and infrequent. Deep is 1 inch all at once. Infrequent depends on the temperature. With temps in the 90s you only need to water once a week. Yes, even in the Woodlands. And yes, even in Phoenix. With temps in the 80s deep water once every 2 weeks. With temps in the 70s water once every 3 weeks. With temps below 70 you can water once a month. This is probably the most important part of lawn care. Once you get the water controlled, then the mowing and chemicals (or organics) will work better for you. I have become full organic and have seen some benefits. If you want to continue with full chemical fertilizers, I would suggest at least once a year you apply an organic fertilizer like corn meal or alfalfa pellets (rabbit chow). These materials feed the microbes living in the soil and make everything work better. These are quite often all it takes to make poor soil healthy again.