My 93 yr old mom lives in a mobile home park and her house is on a corner. She has an area about 5' x 26' on side of house that I have dug out, sprayed, put down weed prevention fabric and then about a 3-4" layer of river rock. The weeds just keep coming - I assume from cars stirring up seeds, birds, etc. as the weeds are not deep down but are overtaking the area. We've sprayed, cultivated...done it all and can't do it any more. Digging out all the river rock is not an option at this point either (took me a week to do it 3 yrs ago and the cost is more then she can handle right now and I live 1200 miles away). I'm going there in 3 weeks and plan on working on this problem. Can I put another layer of weed prevention fabric on top of the river rock and then do a mulch? Someone told me there is a specific type of mulch that has something in it to help prevent weeds. Can you give me some suggestions. Thank you!
Mulch and landscape fabrics work fairly well in keeping weed seeds that are buried in the soil from germinating. However, they do nothing to prevent germination of seeds that blow in from other places, like the lawn, neighboring yards, the field across the street, etc.
I would not add another layer of fabric and rock mulch. We don't want to promote too much water retention there, as this will attract termites.
Existing weeds can either be pulled out by hand, or sprayed with Roundup herbicide. Roundup will kill anything green it lands on, but it will NOT move in the soil and harm the roots of nearby ornamentals. There is a Roundup Season-Long product, but it's expensive.
After removing all of the existing weeds, you can spread a pre-emergent herbicide such as Preen over the rocks. This will help prevent weed seeds from germinating. It's not exactly designed for use in rock mulches, as there is nothing for the chemical to stick to, but it may offer some prevention. This should be done in the early spring and again several weeks later; wouldn't hurt to try it after you've killed the existing weeds.
Be sure to read and follow all label directions.