They will die, get an action hoe. "The key to good gardening is not a green thumb but brown knees" - Read at the Tomato Forum

While it may not hurt the future plants - that is hotly debated as all the previous discussions on 'Roundup' will show - the search will pull them up for you. It most certainly will hurt the existing plants. Just look into all the posts here on weed killer damage.

Tomato plants are especially susceptible to drift from weed killers including Roundup.

Dave

They've only infested the ground where nothing was planted.
Thanks
-TomAndJerryGardener

Weed killer can drift from up to 1/2 mile away. Using it anywhere near the garden risks the plants.

Dave

Please don't use that poison on anything. I guess no one here has heard of Monsanto and the health risks of Roundup. Please do some research.

Tomatoes are the most sensitive plants you can have in your garden. They don't even like to be touched. Forget the round up. It will kill them for sure. Just pull up the grass carefully not to damage the roots or upset the tomato plants too much. Put down a layer of mulch. Grass clippings work real well. My tomatoes like that red plastic mulch.

Second what Dave said, my neighbors RoundUp application a few years ago did in my tomatoes, it's nasty stuff.

Steve

Tomatoes are the most sensitive plants you can have in your garden. They don't even like to be touched.

Where'd you hear that? My plants get "touched" all season long... whenever I tie new growth to the staking, untangle vines growing into one another, pick fruit, remove damaged foliage, check for pollination, squish aphids, check leaves for mites, etc.

But, tomato plants do not like Roundup, and that is a fact.

It does not care what it kills. A good pair of gardening gloves much safer for every one and thing.

You didn't give your zone or how tall your plants have grown in the month they have been in the ground. If you decide to use Roundup (glyphosate), I'd put garbage bags over every tomato plant all of the way to the ground. The drift and effectiveness of Roundup will surprise you and bite you in the butt if you don't. I've been bitten more than once.

The residual effects after it rains and it is in the soil are almost nil. I am a big fan of Glyphosate. I buy it in 2.5 gallon jugs of concentrate. Just stay very, very, aware of drift potential. It's a killer and does it's job well.

Not sure why you would want to put any chemical near your garden.

Scrape the surface of the soil with a sharp hoe to remove the grass. Cover the area with newspaper or cardboard and use rocks or cover with wood chips to hold in place. Once this years growing season is over then you can figure out what control methods you want to use to eliminate the grass.

You don't have to spray the roundup.

You can use a sponge or rag and wipe it on the grass, use gloves of course.

Then you don't have to worry about it getting on anything you don't want to kill.

Pull what you can near the tomato while it is small. Indeterminate tomatoes grow large unless you prune them and will out compete and shade Bermuda this season. In fall or late summer when your tomatoes are mostly done for the year take care of the Bermuda. Use cardboard up to the tomato plant - big brown sheets of it look best- cover it with some sort of mulch. It may be slick to walk on so be careful. I use Round up sometimes carefully near precious plants but it is so easy to accidently get on something or even when you are painting it on drips can fall on a wanted plant. I have Johnson grass in my asparagus and near a viburnum shrub and I have carefully painted it on individual leaves a few at a time gradually working toward elimination.