You definitely want *something* below the ground to prevent grass and other plants from growing under the bed.

Since the 2x4s are free you can certainly use them, otherwise I would go with a longer lasting option such as plastic edging. Replacing the bed with more free wood isn't a huge deal, but digging up and replacing the underground edging is more work and if you don't keep up with it then you have the bed invaded with stuff that won't want to go away.

Depends on the grass and really only bermuda is the truly invasive grass (AKA devils weed). You being in zone 5, chances are you have a Kentucky blue, rye, fescue mix - and only the KBG spreads via rhizomes, but is stopped dead in its track with shade ... like a hunk of wood and a raised bed full of soil :-)

g'day kay,

you could if want to and yes the timber may rot qicker as well, you can also ceate a weed barrier around the beds, that is as i do it is cut away some of the edge of the ground around the base of the bed so you can create an area wher ther is no grass and then lay newspaper down to about 1/2 a meter out and around the bed, then cover it with almost anything you desire ie.,. wood shavings/saw dust, biscuits of hay or straw, stone rubble pretty much anything then all you do is maintain this area and the weed grass can't get near the gardens.

if you use hay/straw this will break down so just refresh it as necessary this area then becomes a helpfull part of the garden as soil structure builds underneath it. check our pic's out there may be some help there for you?

len

Here is a link that might be useful: lens garden page

Thanks. Your answers were helpful. The grasses I have are not very agressive. They do spread without a barrier, an the wood should be just fine.
Thanks again
Kay.