You may want to ask this in Cottage Forum, hopefully they'll have some answers for you. I have the same question!

Once you get your roses established, you will have a thick layer of mulch around them. That should keep the weeds to a minimum. However they will manage to pop up. You can hand pull them, which is what I mostly do. You can put down a pre-emergent in the spring to stop any seeds from germinating (do these spread by seed or underground?).

You can use roundup around roses, I have. There is the possibility of some exposure for the roses. You have to be very careful. I only do it if the weed is something so invasive, RU is the only way to get rid of it.

I've read enough horror stories concerning roses and RoundUp, including RoundUp's ability to transfer from the soil, that I wouldn't let it anywhere near my roses. I have no experience with Mexican petunia but a 12x8 area isn't very big and I would think cutting everything down to ground level and then applying a smothering layer of newspaper or cardboard followed by mulch, over the area and maintaining matters for a couple of months would do the job.

Hi!!
Thanks so much for the help. I am going to dig it all up and hope that pulling them up as they re-grow (they are so thick there is a plant every half inch... they spread underground) will work.

I just recently learned these are on the invasive species list here in FL. I can sure see why.. they are a nightmare.

Since I have such a small area with any shade.. these things have to go!

Love you guys.. I appreciate the posts.

They spread by seeds and underground runner. If you leave even a piece of runner, it can regenerate. I have been fighting them for over six years, and can't seem to totally get rid of them. Just when I think I have them beat, another one pops up.

Make sure you remove the top foot or so of soil when you plant your roses, or they can pop up in the middle of the rosebush. That's what happened to me, and they are very hard to get out of the roses. I ended up letting them grow tall enough that I could bend them over and stick the tops in a jar of roundup. You have to kind of bury part of the jar so it can't get tipped over or that will be a disaster.

Sounds like the buttonweed I have. I can't get rid of it. I actually put round up on a patch of lawn to get rid of it. Yeah, it killed the grass too, but that's growing back.

I hate weeds.

Sounds like the "bindweed" stuff I have! But don't use Roundup. It's a poison,what's more,the company that produces it sells a type of birdseed that is poisonous to birds, I believe. Also, wild animals that innocently eat stuff that has been sprayed with Roundup are then poisoned by the weedkiller.And I gather that the company that makes it tries to convince people that it's "environmentally safe". Sure, sure...
Weeds are a part of the gardener's life,IMHO. Like insect pests, the goal is to keep the situation under control, not "get rid of all the weeds". I think they should be regarded with philosophy...bart

I use and love roundup. I use it judiciously, and it is a blessing. I am familiar with mexican petunia - there are the tall ones with purple flowers and the lower growing ones. The taller ones are the most invasive - had them once, will never grow them again. Other posts are correct - they grow by runners. If I had that problem.....I would spray them with roundup, rake the debris up after the tops died, wait for more to sprout, spray them again. I would keep spraying until no more grew. Hand pulling them to me is an exercise in futility and if you dont stay at it, they will take over. It is doubtful you will get rid of them by digging them out or pulling them up. Its not like you will be doing this all the time - just to kill the petunia. I raise horses and have 30+ acres, so I fight weeds all the time. Weeds are a part of life in a garden, but I dont have time nor inclination to fight a pest like mexican petunia. I am doing some new beds and I kill the little emerging weeds with roundup spray - once they are dead, I put rotted horse compost then my soil mixture of mushroom compost, bark fines and sand. That pretty much solves the weed problem and I have an excellent soil mixture to grow things. I had a little crawling weed that made a little strawberry looking thing.....huge pest! It was just in one area of my yard. I spot sprayed roundup on it until it finally died and I am now rid of it, but watch closely - if any should pop up I zap it. There is a product called Relegate that I use to kill tallow trees in my pastures - they are a horribly invasive, hard to kill pest of a tree. I had a little in my hand sprayer that I used on some smaller weeds - even with no wind, the aerosol from this product will travel to other plants so I only use it in the pastures. Roundup, however, is not like this. I do understand many people wont use this or other chemical sprays, but it is a godsend to me. And once I get the weeds killed off.....I pile on the compost and good soil and dont have to use it again on that bed.

If you have an invasive plant with runners, I have found that RU won't go deep enough to kill the roots unfortunately. It will kill off the tops, but will resprout.

I planted an innocent little perennial called 'Chameleon' a few years back. Little did I know it was an invasive thug that would take over and spread everywhere by underground runners. After years of futile digging, my hubby put down heavy black plastic and piled mulch over the top of the plastic. The plants couldn't get through the plastic because it smothered them. I could cut through the plastic the next year and plant roses and no more 'Chameleon' plant. That plant should come with a warning label!

Use it.
Use it carefully.
Use it only where you need it.
Target it very carefully to the green growing part of the plant you want to get rid of and repeat when you see regrowth.
I have eradicated Bermuda Grass using Roundup, and it's a tough bugger.
If you think you have gotten some spray on something you didn't want to kill, prune that part off immediately.
RU can be your friend, but you must use it very very carefully or it will turn on you.
There is a method called "the glove of death" which you can use if spraying makes you nervous. Google it.

Buford, there's a broad leaf weed killer that will kill only weeds and not your grass. The brand I use is Weedmaster. I use it along the fence lines in my pastures.

The plant you are looking at is botanically called Ruellia. It is a known invasive plant (as you have found out) and should be eliminated. That is easier said then done. I told a friend of mine in another state that she shouldn't plant the Mexican Petunias and she went ahead and did it anyway. At first it was meek and mild, but after the reseeding began she regretted planting it for years to come. Round up will work on the existing plants, but if this has been around for awhile, you will have seeds laying in the soil that will sprout for years to come. Here's an article about it from the Florida Native Plant society....Maryl

Here is a link that might be useful: Mexican Petunia

I use RU but only along my walkways...never ever near my roses! For weeds in my rose-beds, I use roofing shingles-- lay them on the weed and leave them for several weeks, and the weed is suffocated and toasted by the sun... the shingles are heavy and don't blow away, and last for years- just move them around the garden as needed, they are black and inconspicuous, or put a bit of mulch on them to hide them....I get the packs of shingles at HD for abt. $28. and it is enough to work the whole garden (150 roses)... this works on anything that grows, grass, weeds w/runners, etc. sally

Ha, TerryJean - Houttuynnia cordata 'Chameleon' was it? Horrible swinish running roots. What a 'mare.

Yes, it was that dastardly plant, Camp. I loathe that citrus-y smell when you pull those suckers that go clear to the bowels of the Earth and then break off. Even after 5 years, a little rootling will sometimes re-appear.

I second everything that Landlady has said. Round Up is a great tool to be used in certain situations, and it is safe as long as you apply it carefully to only the weed you want to kill.

Years ago, when I had an outbreak of a low-growing weed on my gravel paths (I don't remember which weed it was) I went so far as to use a paint roller to carefully apply the Round Up only to the weeds on the paths.

Weed control is a multi-step process. You must kill or remove the ones you have, then do what you can to prevent them from returning. Sometimes a careful shot of Round Up applied by a conscienctious gardener (RU is innert in the soil and is labeled as to not transfer from place to place in the soil) can save you hours of digging and the frustration of having weeds return from pieces of root that were overlooked.

Round Up is a tool. Use it wisely.
Connie

P.S. Ornamec is a selective herbicide that kills grass only, so it is perfectly safe to use around roses and other broadleaf plants (read the package insert to make sure that your plants are on the safe list). It kills Bermuda and crabgrass particularly well, while leaving roses completely unharmed.

The following was stated: "(RU is innert in the soil and is labeled as to not transfer from place to place in the soil)".

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Here is one full paper (not just the abstract)
http://wiki.community-harvest.org/images/e/e8/Laitinen2007.pdf

Also please read starting on page 31 what a recent Ph.D. thesis has to say about "Rhizosphere transfer of glyphosate from target to non-target organisms".

http://d-nb.info/1007899328/34

Here is a link that might be useful: 2009 Ph.D. thesis

Another group seems to be interested in Round-Up.
http://www.thetriallawyermagazine.com/blog/viewpost/422
"A decade later, in 2007, Monsato was fined in France for misleading the public about the environmental impact of its flagship herbicide Roundup. A former chairman of Monsanto Agriculture France was found guilty of false advertising for presenting Roundup as biodegradable and claiming that it left the soil clean after use. Monsanto�s French distributor Scotts France was also fined 15,000 euros. According to a report from the BBC, France�s Supreme Court upheld that verdict in 2009."

Here is a link that might be useful: trial lawers

Roundup is dangerous to fetuses, gets into ground water, and the spray drifts on the slightest wisp of a breeze, easily damaging roses and other nearby plants.

Just sayin'

The trial lawyers' link seems to be down. In case it does not come back, the link started out with a discussion of the following 2012 Parkinson's disease paper:
http://www.sciencedirect.com/science/article/pii/S0892036212000438
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Another 2012 Parkinson's disease - glyphosate scientific paper:
http://www.springerlink.com/content/k04267614g27062l/

Here is a link that might be useful: paper first discussed in lawyers link