Although you may think that you'll be done with weeding when you switch from a real lawn to artificial grass, weeds may still be a problem. You can make this less of an issue by getting rid of any weeds before you lay your new grass; adding an extra layer of weed matting may also help.
The Benefits of Weed Matting
Weeds won't be as much of a problem on synthetic grass as they may be on real grass, but they may still pop through occasionally. For example, a weed may be able to find its way on to your grass through ventilation holes or spaces in the turf.
Weed matting is a sheet of material that sits under synthetic grass, giving an additional level of protection against weeds poking through your lawn. The membrane of the matting ensures that there is nowhere for the weeds to come through. If you have a significant weed problem in the area where you'll put down the grass, this may help get rid of it.
Tip: If you're having synthetic grass installed by a company, ask if it recommends a weed membrane.
The Drawbacks of Weed Matting
If you don't have a lot of weeds in your garden, you may not need to put down a weed mat. Dealing with the odd weed that does manage to get through synthetic grass won't take up too much of your time, and you aren't likely to suddenly develop a major weed problem with this kind of turf.
Tip: Weeds are more likely to grow on your artificial grass if you allow it to become clogged up with leaves and garden debris. Get into the habit of raking leaves off your grass regularly and brushing it to keep it clean. If you do get weeds growing on or around the edges of your synthetic lawn, remove them as quickly as you can. If you plan on using weed killers near or on your grass, make sure to use products recommended by your installer or the grass's manufacturer to avoid damage.
However, if you have dogs or cats that will use your grass as a toilet, a weed mat may not be a good option. Pet urine may soak into the membrane under your grass. While it's relatively easy to hose urine off artificial grass to prevent it from drying and smelling, you may not be able to get rid of it if it soaks into the membrane under your lawn. Over time, the membrane itself may start to smell really bad, making your garden smell like a pet toilet.