Down here the farmers burn their fields annually to remove thatch. I don't know if you can do that as a home owner.

The cloth might not be impermeable enough. A lot of people have success using a heavy layer of cardboard, newspaper, or brown paper bags with success. I've used newspapers in the base of my raised beds, and paper bags as the bottom layer in my lasagne beds with success.

If your bed is really infested with roots- that might be part of the problem too, because with some weeds, no matter how much you remove, if you don't remove it entirely it will keep coming back from even tiny bits of roots.

@BeesNeeds. Thanks for the idea. How quickly does the cardboard decompose? It would be a pain to have to keep redoing it. That's why I bought a synthetic cloth liner so that it would be semi-permanent.

What plants roots are invading your beds?
Just wondering - if trees, that would be bigger problem.

Cardboard would help some, but you should probably have quite a few layers as BeesNeeds already mention. All of it will eventually decompose, so depending on thickness of layer you will have to add again sooner or later.
There are different cloth liners, which one did you use? How big is the bed?

removed dp

This post was edited by rina_ on Thu, Jan 29, 15 at 12:12

Hi Erica,
Can you post a pic (it is worth a thousand words) ;-)

Cut a notch about two feet deep, and drop a piece of polycarbonate plastic sheet in. It'll last just about forever. Or find some discarded corrugated galvanized metal roofing. If your tree roots run deeper than two feet, they will still get in.

Your other choice is to cut a deep notch every year. That will cut all the roots, so they will never get big enough to take over.

A veggie garden is hardly worth all this trouble and expense. Can't you find a better location?

@lilydude. Thanks for your advice. (No, there's no place else, I've got a tiny yard). When you say "cut a deep notch", do you mean just cut through the soil around the edges of the bed to break off the opportunistic roots where they're infiltrating? I've tried that but they come back very quickly. I don't understand the instructions re: the plastic sheeting -- "cut a notch two fee deep and drop it in" -- cut a notch where and drop the sheet in where? Thanks for clarifying!

Are you sure the roots are coming from the outside? This is a raised bed and the roots may have been under there all along. What did you do to the soil you put the raised bed on?

tj

Cut a notch along the edge of the raised bed where the roots are getting in. Drop a piece of corrugated polycarbonate or metal roofing in, so it is separating the outside soil from the raised bed. You don't need to backfill. Roots will not be able to grow horizontally into the bed. But if the roots are growing below the level of the notch, they will go under the corrugated panel.

Or you can cut a notch every year without installing a panel. That will keep the roots from getting established in the raised bed. The roots that are cut will eventually rot. If you have a tree that develops stems from the roots, this won't work.

Sorry I haven't checked back into this thread sooner Erica.

About cardboard. I don't know how it performs under beds. I've used heavy duty cardboard, like the stuff appliances or heavy shipping comes in, as walkway between beds, and that's lasted in a single layer for several months- I just laid it last summer. I've laid lighter weight, like moving box weight, under some pavers to help kill off the spot where those pavers are going to finally go in, and that's lasted about a year so far. That's been sitting so long because I haven't finished making all the pavers yet.
All this cardboard has been corrugated cardboard, so it in itself is a couple "layers" thick between facing, backing, and the corrugated layer. But I still used the stuff double layer, by essentially just having the box flattened in half. I have no idea how well thin cardboard would work, like the cardboard cases of soda cans come in is thin cardboard.

For under my raised beds, I've used several layers of newspaper. I think around 7-10 sheets thick, and overlapping by a couple inches along with going up the sides of the box by a couple inches. I also pre-killed the area with plastic for several months prior to putting in the raised beds.
For my lasagne beds, those just got built right on the grass. I used a double layer of brown paper shopping bags, again overlapping by a couple inches and extending beyond the bed by a few inches. I've done the double layers in two ways- one bed was created by cutting the bags open and laying them out, the other was created by just leaving the bags whole in their folded state and laying them out. Leaving them whole uses up a more bags, but the layering is thicker so I think it works more effectively as a weed barrier.

With both these methods, I've started from scratch, and built up the bed on top. If I were to try it with an already existing bed, I would remove the contents of the raised bed, and start from scratch refilling the bed with fresh material on top of my paper barrier for best results. I don't know if that would be possible for you or not.