We just moved into a home that had three existing garden beds. We're using them for vegetables. Next year I was thinking of building a new and smaller bed to use for herbs. I saw a video from Lowe's that seemed to show a relatively easy way to build a bed. After removing the sod they roll out landscape fabric that will sit under the soil in the bed.
What is the purpose of using landscape fabric? And more specifically, would it be useful in a vegetable or herb garden bed?
Without looking at your video, I would expect the landscape fabric is being laid as a weed mat to inhibit weeds from regenerating from roots left in situ and coming up in the middle of the raised garden bed.
Some people use layers of newspapers, and others old wool carpets.
One of the main reasons people build raised beds for vegetable gardens instead of planting directly in the ground is because it's often easier to fill a raised bed with a good soil than it is to try and improve poor soil in the ground.
Raised bed are commonly filled with either good topsoil and compost mix or something more like a soilless or a peat-based potting mix. I use a peat based potting mix for a raised bed I do square foot gardening in.
In either case the soil in your raised beds will be nicer than the soil in the ground. Nearby tree, shrub and plant roots may find their way into your raised bed soil and realize how nice it is in there and decide to stick around. They will compete for water and nutrients with the plants you want to put in your raised bed. The landscape fabric will help keep them out but some roots may still find their way in. Landscape fabric doesn't last forever either.
The depth of the soil in the raised bed should prevent weed seeds that are in the existing soil underneath from germinating.
If you have burrowing animals like gophers you may also want to use some hardware cloth on the bottom of your raised bed too.
I'm building a nice 12' X 3.5' X 23" asparagus bed. I'm using 12' X 5" X 11.5" beams. I hope that the bed will be productive for many years so I'm using hardware cloth and landscaping cloth underneath the entire bed to protect the bed from weeds and little varmits of the tunneling variety. I wish I had done it years ago but now is better than never.
I use landscape fabric to make my raised beds. I attach the fabric to galvanized welded mesh and then overlap the ends of the mesh with the fabric on the inside and attach them with galvanized baling wire. It ends up looking like an above ground pool filled with dirt, but is a cheap and easy to move circular raised bed. The fabric sides also air prune roots and facilitates draining making overwatering much less likely.
