Every little piece of stolon from bermuda grass grows a new plant after tilling. Tilling before a freeze, then tilling again before a freeze might work, but too late for that. Also, solarizing (clear plastic laid down for a month, or a season) also too late for that if you want to use the plot soon. Try cardboard covered with some other mulch. If you haven't planted yet, go through the soil and remove all roots and stolons. I don't believe you ever get rid of bermuda grass in Oklahoma, you just keep pulling it up.

The methods for removing Bermuda grass can likely be separated in two general categories: multiple spraying of non-organic herbicide on warm sunny days or labor intensive digging. The way I start a new raised bed (or would deal with a raised bed that is infested with established Bermuda grass) is to dig out the top soil to a depth below the roots and set it aside. I pile the dirt with the Bermuda in a shady spot on the north side of my house, and after a year or two, the Bermuda dies because it does not like shade. I then refill the raised bed with organic material and soil that no longer has the Bermuda grass.

In your situation in a community garden, you might not have the ability to set the soil aside, have access to Bermuda free soil, or want to buy new soil. Therefore your best bet would likely be the labor intensive process of digging all the soil out of the raised bed, pull out all of the Bermuda grass paying close attention to get as many of the roots out as possible. Then put the soil back into the raised bed. You will then need to be very vigilant of any Bermuda that tries to grow and pull it out before it can get established. If your soil stays loose, as it should in a raised bed, it is relatively easy to pull out any Bermuda as long as you catch it early. One tiny Bermuda grass stolon, left in place and given time can overrun the raised bed.

Thank you for your responses. The Bermuda grass is stealing my rose colored glasses of spring. Each spring, I believe that this year's garden will be perfect. Of course, it doesn't last, but I would have liked for the feeling to last a wee bit longer ;)

Rototilling is the worst thing you can do with bermuda grass because even if you leave only a 1/4" piece of stolon every three feet or so, that is enough to enable the bermuda grass to completely take back the garden plot in just a couple of months. Hoes don't particularly work with bermuda grass as they often chop off the top growth and leave the stolons beneath ground.

One way to (maybe, success not guaranteed) get rid of it before planting would be to rent a sod cutter and cut out all the bermuda sod/dirt in late winter/early spring before attempting to plant. That's similar to what Mars described but it doesn't involve digging---the sod cutter does it for you. You would have to use the sod cutter deeply enough to get out all the stolons. Then, to make up for the soil removed with the sod cutter, you'd have to bring in compost and other amendments to refill your garden plot to at least its original depth. I doubt that I would go to that much trouble for a single plot of land in a community garden unless I could keep the same plot year after year. What I'd do in your shoes is just keep digging it all out. It will keep coming back, but if you religiously dig it out before it becomes too deeply entrenched, eventually you realize that less and less is coming back each year. If the soil is soft enough that you can pull it out, pulling could work but often when people think they are pulling bermuda grass out, all they're doing is pulling runners off the stolon and leaving the stolon behind so make sure you aren't doing that.

If your community garden allows the use of herbicides (some do, some don't because of herbicide drift issues), you could kill the grass with a herbicide, following label directions and carefully applying so no drift travels to adjacent gardens and kills their plants. Personally, because of herbicide drift, I'd never use a herbicide in a community garden area. I live on acreage in a rural area and I don't use herbicides either, but still get plant damage'plant death from people using them nearby---often multiple times a year.

If you haven't planted yet, you could put down landscape fabric, cut holes in it where you want the plants or seeds to be planted, and plant. You would do this after you already had removed all the bermuda grass stolons to the best of your ability. Then cover the fabric with mulch a couple of inches thick. This isn't foolproof, but in a very weedy area it can help a great deal. You still will have to deal with weeds that come up in the cut hole areas beside your plants or seedlings, but it still will cut back on the weeds a great deal. You also may have weed seeds blow in or wash in during heavy rain and sprout in your mulch, so you'll have to pull them out before they can grow down through the mulch and through the landscape fabric.

Dealing with bermuda grass is just a fact of life in this part of the country as it is incredibly aggressive and you cannot ignore it or it will take your garden plot away from you.

I can tell you from personal experience that laying cardboard down and covering with mulch won't deter Bermuda longer than a few weeks. Unless it is a HUGE, THICK layer of cardboard, the Bermuda WILL find any crack or opening and by fall cover your cardboard/mulch with a very healthy mowable carpet of grass.