I looked long and hard at Trex decking, but the cost to buy as much 2x6 special order would be thousands and thousands of dollars. As it was my beds cost about $500, so much for penny pinching as the book says. Even the 1x6 decking is expensive.

Besides cost issues, all Trex like product bows badly (it's plastic). I'm sure it would work for 4x4 beds but I wouldn't use it for any bigger boxes.

I used pressure treated 2x6s for my beds. I went that route for strength and durability. Going 11 feet with anything less would have bowed with the weight of all that dirt. Thus the vertical supports every 4 feet.

Here is a link that might be useful: Pics of my beds...

I like sinfonian's boxes...nice & deep. Well made too.
Anyway, all new lumber is pricey these days, and weather resistant woods like cedar or redwood are the priciest. Even pressure-treated boards are something like 7 - 10 bucks for each 2x6x8ft board. And some people have issues with pressure-treated wood and vegetable gardening.
Since it is Winter and you have a few months til Spring, keep your eyes peeled for people recycling wood from decks or houses or barns or whatever. In VA you're unlikely to find any redwood but you may get lucky and find some usable lumber sometimes for free or cheap. That's how I do it. It is quite interesting what people are happy to get rid of. Check craigslist or local newspaper classifieds or check out house demolitions or ask around.
You can also use less weather resistant types of wood...they just won't last as long. But they will be cheaper. Or find another way to keep your soil contained...reinforce old pallets, use cinder blocks, etc.
From what I know of TREX, it is easy to work with and I'm not sure it would bow more than any other wood since you're just using it to contain dirt not support the weight of dirt. But it is probably pricey. It would look pretty darn sharp though. And it would last for many many years.
I built my deck with new redwood. A couple years later I found a person giving away lots of redwood from an old deck and rented a truck and took that home and used it for planter boxes and raised beds for me & my friend. That was sweet!
Good luck.

The thickness of the TREX decking is most likely going to lead to bowing. They are only 5/4", similar to decking lumber. Some brands are even sold rolled up! If you were willing to put in good stake supports every 2 feet or so, you could fight the bowing pretty effectively, though. They do have a 2" product, but I would think the cost would be pretty darn high.

Bryce

Call local sawmills and see what they have. If you are somewhat west in VA there will be plenty of them. They may have native hemlock which holds up pretty well, or white oak for sure which will also last a good while. Often they have stuff stickered and fairly dry for not much more money, or you can let it dry for a few months after you get it. A quick way to dry wood if it's short enough is to stand it up in your basement. A barn or shed is better if you have one.

Hey folks,

Thanks for all the replys. Went to Lowes yesterday and looked at Trex. It's waaaay too flexible AND cost prohibitive for raised beds. Shoot, it might be too expensive for just about anything! - $40 for ONE 5/4x6x8. The other choices there are Pine or PT Pine - that's it. I don't think a softwood is going to last very long. So, all Lowes really had to offer is PT Pine. I'll have to research that one a bit - not too excited about using PT, but I'm not totally against it (yet).

I like the Lumber Mill idea. I actually have three within 10 miles or so. I've only been to one but that was to buy firewood a few years ago. I don't know their pricing, but they do have more varieties to choose from (Hickory, Red Oak etc). Guess I'll give them a call next.

Thanks for all your thoughts. I appreciate it!

All PT is yellow pine, which is more naturally rot-resistant than the soft pines and spruce. Trex is chemical-filled garbage, as well as expensive.

Native stuff at sawmills is generally pretty cheap. You should be able to find hardwood at less than $1 per bd ft. Red oak rots quick, be sure to get white oak. I don't have much experience with hickory but I believe it has some rot resistance. Beyond the wood species, remember that sap-wood rots far quicker than heart-wood, so it will be worth it to rip the sap-wood off the bottom of the first piece where it rests on the ground. And if you rest it on a little sand or gravel that will make a big difference also. Obviously the sawmill owner will be able to tell you which native species are most rot-resistant.

Auctions are another place to check. My DH goes to every auction that lists lumber and has stockpiled a pretty impressive inventory for next to nothing (it helps to have a good pickup and a willing neighbor to help load!)

I have built raised beds from Trex decking and it works great. There is no bowing in my beds, which are 8' x 4'.

They are joined with a bracket.

What's worse (now you really will hate me, LOL) is that I got a huge stack of it for free. Yes, a wealthy neighbor didn't like the looks of it so she tore out a deck that was only about two months old. She gave me the whole stack of decking that was thrown out. I can build raised beds until hell freezes over.

Another bonus with using this Trex decking stuff is that it's easy to saw. Not so with wood. So women like me who are not too swift with building stuff can easily pull this off.

When I get my camera fixed, I'll take some pics and come back and post them.

Cher in NJ