Good luck. I have bermuda growing two feet under a concrete walkway that separates my front lawn from my front flower bed.

I think the only way to deal with BG is to periodically pull it up before it gets too established. Having organic material and keeping the area moist at least makes it easier to pull up.

Yes, that's a good start. But as you say, it can be overwhelming in summer with it grows like wildfire.
Bermuda grass is my enemy #1. (Nut sedge is #2) I finally got control of it by using large cardboard pieces 2 or 3 layers thick. Stager/overlay the seams and breaks so that it can't come up between pieces. I also put mulch over the top to hold them down. Good size flakes of straw or spoiled hay are my favorites.
The big cardboard from things like washing machines and appliances are great. Also the boxes that paper towel and t.p. come in at the supermarket. Great big pieces with fewer seams so it's easier to keep it from coming up between.
Once when I had a huge area to do I purchased a load of damaged drywall sheets (had gotten wet so could not be used to build with. Got it for $20 to have someone deliver it) these were wonderful since they are so big, but very expensive if you have to buy new. When they break down, the gypsum is good for the soil.
Once you have the major problem licked, you have to become compulsive. Even the smallest little sprout that tries to start must go! I grow dates and if you drive around our area you will not find a date garden that doesn't have bermada... except mine. I remember one offshoot that had some growing right in it and I pulled that stubborn little thing 20 times if I pulled it once. But in the end, I won.
Remember it can send a root runner 20+ feet underground 4 to 6 inches down with a node just waiting to sprout every inch, so when you start pulling, remember you will be back at that spot several time before there is real and lasting victory. Hope that helps.
Good luck!

I've experienced some of these tough grasses (don't know what all mine are but I'm sure bermuda is one of em as it is quite common down here.) Anyway, the stuff that is sending rhizomes over/through your mulch are the easy ones to pull. The stuff that is comming up from below and makes it through everything are nearly impossible to get the roots without some major forking.

I do recomend using a fork to help find those rhizomes without cutting them up too much as larger bits are easier to sift out.

As for a barrier, look into bamboo rhizome barriers. I've installed some of it before for bamboo (it was 48" wide and quite thick durrable plastic.) If you can get something less than 24" wide and perhaps even slightly thinner it will cost alot less. Whatever you use, you want to angle the barrier so whatever you are trying to stop will hit the thing and go up so that you will see it to cut. If the barrier sends the rhizome down, it will be deep under the bed before it comes up and totally defeat the purpose. Also the seams should be secured such that the rhizomes can't wiggle their way in.

Good luck

I guess I'm surprised so many people have so much trouble killing bermuda in garden beds. Killing it out of an established lawn is a huge issue, but killing it in bare dirt is simple. Bermuda requires FULL sun to grow and thrive. If there is a tree or building to the south between you and the horizon, you have a pretty good shot at killing it out. All you need is shade.

My neighbor killed her hybrid bermuda front lawn for two years by applying too much compost. The compost shaded out the bermuda. After two years of a really horrible looking lawn, they replaced it all with St Augustine.

Just this year I killed a 500 square foot patch of bermuda by smothering it with sand and mulch. We had just finished remodeling last winter and the bermuda filled in where the contractors were working. We needed to relevel the area for drainage anyway, so we brought in sand. The sand ranged from 6 inches deep against the house out to zero inches deep at the edge of the stone driveway. The mulch was 2 inches deep next to the house and out about 10 feet, but then we put in a row of bricks at the edge. The bermuda was growing at the time and we received 50 inches of rain in the 100 days of summer. Although the bermuda was plush out in the (formerly) rock driveway, it never came up through the sand and mulch.

This was not a Herculean attempt to kill the bermuda. It was straight forward gardening. We were prepared to pull bermuda shoots as long as necessary. We had less than a handful spring up where the mulch/sand combination was very thin under a huge rose bush. Those were in deep so I know they were volunteers from below. The bermuda creeping in at the edge is extremely easy to pull out of mulch and sand.

The main problem is when you have a flower or vegetable bed bordering a lawn of bermuda. Most of my yard is full sun, including the flower beds, so the bermuda will grow there. The bermuda will continue to creep into the bed at the edge, which is why regular edging with a gas edger to get 4 inches down is necessary. Still I have to pull up strands that get into the bed from lower down. And as I said, even with a 2 ft wide concrete walkway between the lawn and rose bed, the grass manages to creep in from underneath.

I have 'killed' bermuda in the backyard, which closest to the house gets little sun. I still had to round it up to get rid of it for good before putting pavers down. It doesn't grow well in shade but it will continue to put out shoots from where it is growing well.

If you going to have a bermuda lawn, and flower beds, you have to be constantly vigilant about pulling up stray shoots to keep it from becoming established.