Question
Hi and thank you in advance!  I have shrubs that I planted in a rock garden and I put that weed screen on the bottom so weeds would not grow, well, needless to say last year I still got a lot of weeds growing up through the rocks.  This Spring is there any product out there that I can put on top of the rocks and stop the weeds before they start?

Judy

Answer
Hello,

I would suggest that you weed by hand and use mulch and you might want to experiment with solarization. Solarization consists of putting down a layer of clear plastic over the soil. The weeds and their seeds are killed by the heat that builds up under the plastic. Follow these steps for solarization:

Uproot existing weeds.

Remove the uprooted weeds with a rake,then rake the soil again to smooth it. Wet the soil. Wet soil conducts heat better.

Cover the area with clear plastic sheeting of 1 milimeter to 6 milimeters thick. Hold down the sheeting with rocks,etc.. and make sure no gaps exist in the edges of the sheeting. Leave the area covered for 4 to 6 weeks.

The best time for solarization is June through July because thats when the sun is hottest,but solarization can be done all year. However,solarization done outside the June to July range will take longer. For cooler weather,leave the plastic in place for 8 to 10 weeks.

There is nothing I can suggest that you place over the rocks,except perhaps the clear plastic for solarization. I would not suggest any kind of impermeable membrane for weed control,such as black plastic because the soil and plant roots need contact with the open air. A weed barrier combined with mulch may be more effective than  a weed barrier alone. A weed barrier is designed to be used with mulch. The weed barrier is permeable. It has tiny holes throughout to let air and water in,but this also allows a certain number of weeds through. Pine straw mulch has an excellent track record at suppressing weeds and is resistant to wind. It retains water well and takes a long time to break down. Good luck.

Mark  Harshman
http://www.mahdrafting.com
Email: [email protected]

http://www.scribd.com/markscrib47