Yes, you could use either. Personally, I'd stick with the Preen if given a choice. Casoron can have an effect on existing plants as well as deterring new weed development. It is extremely persistent in the soil and its effects could be ongoing. It also carries a higher toxicity rating than Preen and can present some health issues as well. Just not a good product all around.

How about a nice organic mulch instead? It suppresses weeds, keeps the soil more evenly moist, and in the long run it adds organic matter to the soil. I find I need to do very little weeding in mulched beds and my plants are happy as well.

I do use mulch what I'm battling now is Johnson grass and Bermuda grass It grows up through over and around everything, it even has grown up against our house and has a sprout under the bottom plank of our siding! has grown 3 to 4 feet up in our aborvitae that all has to be hand pulled.

Next to the house there is black plastic with river rock, it has been a while since I have seen it though once the grass moved in I spray 3 times a summer but back it comes, there is at least a 3 to 4 inch layer of just tangled roots so close to the house its impossible to use a tool to get it out, any suggestions are welcome.

There are also herbicides that target grasses (monocots) specifically. Grass-B-Gone is one brand but there are others. These can be quite useful if you have grass growing into planting areas, as it won't harm other, broadleaved plants. And edge the lawn regularly to keep it where it's supposed to be!

Sometimes you just can't avoid a proper clean out of all weeds. It may make sense to remove the rocks and plastic and clean out the weedy roots. Then apply your pre-emergent and mulch or whatever to cover the soil surface. River rocks are hard to work with as they inevitably collect debris and promote weed growth that is difficult to remove. And landscape cloth or plastic has minimal benefits as far as weed control is concerned. Most consider it more of a handicap than a helper.

If you use something like Grass-B-Gone just be sure that you don't have "good" plants that it will kill such as ornamental grasses. There are other ornamental monocots (lilies, daffodils, bananas, palms, just to name a few) and I don't know if they are susceptible to this type of herbicide. The directions should tell you or you can do a web search or perhaps GG knows.

Nope - any monocot will be affected so keep away from the type of plants Babs mentions.