building flowerbeds: remove St Augustine 1st or not?

To create beds, landscape contractor cut st augustine down to the runners, then laid landscape fabric, then cut holes in fabric for trees & lg. shrubs, then added good top soil & mulch). Can I expect slow growth of new plantings since grass not actually removed 1st & all will be growing in gumbo? I'm in zone 9, greater Houston TX area. I suppose over time I can add compost/organic matter under fabric to help break down st Aug runners. Comments/thoughts welcome. This is my 1st post! Gardening is my passion!

Honestly I'd probably get rid of the landscape fabric--it does help keep down the weeds and will prevent the grass from coming up but it interferes with normal soil biology to some degree, the soil underneath it won't be as healthy as it would be if you got rid of it. I'd use newspaper instead of the fabric--it performs the same beneficial function of keeping weeds down and killing the grass, but it's better for the soil. Only trouble is it doesn't last as long, but by the time it breaks down I think the grass will be dead. I don't know much about St. Augustine grass, I know Bermuda is impossible to get rid of but most grass if you smother it in newspapers and mulch that'll take care of it pretty well.

Luckily, St. Augustine grass is shallow rooted, (UNLIKE BERMUDA)...as long as the old runners are buried and don't get any sun, it probably won't come back. What your landscaper did will probably be fine...just leave it and see what happens. I doubt it will resprout.

I think that the grass will die with no problem, but I think you will not like the landscape fabric in the long term. Everytime you start to plant a new plant, you have to cut a hole in it. Hopefully if you continue to add dirt and compost, it will give you lots of good soil to work with. As far as the gumbo, you will find that some plants root extremely well and deep in the gumbo, others will grow well, but keep alot of roots closer to the surface.

Good to see some one so close!

Try lasagna gardening using thick pads of newspaper as the smothering mulch over and under layers of peat moss. I also use a compost/manure combo and sprinkle in a bit of bloodmeal and bonemeal. Plant through the first layers and finish it off with shredded bark mulch. Keep moist and you will have a blooming garden in a very few weeks.
If you have access to other free mulches, such as grass clippings, shredded leaves and rotted straw, shredded seaweed and kelp, or the powdered versions you can also use those. The author (below) uses up to 9 layers, but I use only 3-4 and it works fine. The newspaper breaks down over time and helps condition the soil. It does need to be renewed periodically for weed control, a great way to recycle your papers. Making your own compost also saves money.
You can plant right away or do it in the fall and let nature take its course over the winter. Your bed will be ready by spring.
I got this idea in June 2000 from a book called Lasagna Gardening by Patricia Lanza. It is mentioned in the Bookworm section of this website. I added my positive comments today.

I have started all of my garden beds by putting 4-5 layers of newspaper right on top of the grass, then a 3-4" layer of farm post (composted horse manure and bedding straw). That is it. I usually plant right away. The only weeds I get are those that blow in on the wind and the landscape fabric won't take care of that.

I think that landscape fabric sticking out around the edges of the garden and plants looks awful and the newspaper decomposes never to be seen again. Also when you plant you have to fight with that fabric.

The grass runners will decompose on their own, but I personally would start to gradually get the fabric out. Put the compost on top of the soil when you add it, it will help keep the weeds down while nourishing the soil.