Why I rarely use landscape fabric
Far too many times I see landscaping fabric used for the wrong application. There are cases where the use of landscaping fabric is justified. Using landscape fabric in the correct way will help eliminate future problems down the road.
It is important that nothing will completely stop weeds from growing. Organic matter will find its way onto any surface. Seeds get carried on the wind and passing animals. Weeds will find their way.
Do not use landscaping fabric below bark mulch
This is the most common application I see fabric used for. The problem with this is that bark mulch is organic material that decomposes and creates a home for weeds. So like any garden bed, reglar maintenance will need to be done.
Removing weeds actually becomes more difficult with fabric installed. Roots attach themselves to the fabric and are harder to pull out.
Perhaps the most important reason landscaping fabric should not be used under mulch is for the health of the plants. The fabric crates a barrier where nutrients from the decomposing mulch cannot enter the soil below. Both nutrients and small organisms are kept from the soil below. This creates a dead zone right below the fabric, not very beneficial for our plant health.
When to use landscaping fabric:
There are a few applications where fabric is justified. The most common is under rock. Wether it is crushed rock, river rock, or lava rock, fabric keeps the rock from mixing with the soil below. If you plan on having rock in a garden bed, by all means go ahead and use fabric so or you will be topping up on rock each year when they sink into the soil.
There are some other times fabric is recommended. For example, when laying artificial turf or laying paving stones, I will put down a layer of landscaping fabric before my other materials. When making a pond, a layer of landscaping fabric is great beneath the pond line to keep any sharp stones in the soil from puncturing the rubber membrane.
So fabric is not so bad. Provided it be used to separate materials like rock, and not a weed barrier with mulch.