Just like pain...everyone seems to have a different tolerance.

If you are not too picky....I say use whatever you have or can get free or reasonable.
Using the search feature at the top of the forum you will find enuff to cause total confusion. I linked MY fav below.

I recently saw someone on Craigslist who had excess Trex from a deck project but that was in CT. It may be worth a shot if that is what you want.

I do NOT see how any composite could get termites. Might leach something else into the soil but termites? Kinda curious where you heard that?

Just plain would wood (ha) give you 5-8 yrs, I am sure.

Good Luck in whatever YOU choose.
Gumby_CT

Here is a link that might be useful: Borders for Bed Gardening

I agree. Decent wood should last you a few years. Otherwise you can use concrete cinder blocks. Go to a supplier and if you want to save money, you can ask if they have slightly damaged ones. They often sell these at a good discount and you don't lose functionality.

If money is no object, you can look in deck material made from recycled plastics which will last a lifetime.

Over the years I've done uncontained dirt mounds, 2 by X wood of several types, large rocks, standard concrete blocks, RR ties, landscape timbers, used tires, discarded water heaters laid on side, and a few other items. They all worked, more or less.

For the last few years I've gone to poured in place concrete. Strong (no need to be careful with the shovel), permanent, not that expensive, and where called for they can be dressed up to look nice.

A 4" thick, 12 to 14" high wall is about $2 a running foot, say $65 for a 4 by 12 bed, for the plain jane type.

I use cedar. Pests don't bother it and it takes a long time (10 years or more depending on climate) to rot to the point it loses structural integrity.

If you want to stay away from wood entirely due to termite concerns then use the synthetic deck material or cinder blocks or poured concrete as pls8xx suggested.

Personally I like the idea of cinder blocks. They can be painted to look nice and the small 'pockets' can be used to grow drought tolerant plants as an added bonus. They will last pretty much forever.

For what it is worth, my first raised beds I made about 5 years ago I went on an ultra cheap way. I used 1/4 inch plywood cut to 12 in. with 2x4 every 4 feet sunk into the ground. I later found out that every 2 ft worked better. They lasted 5 years. This year I did them with 2x10. They should last a bit longer, but were really expensive. I think when I redo them next time I am going to spring for concrete block and do it once and for all. It will last forever that way.

to add to my previous post I don't believe composite materials would get termites. I think you got bum info there. Cedar and redwood are unlikely to get them either, but composite materials simply lack any food for them so I consider it extremely unlikely. Get a second opinion if composite material is what you wish to go with.

I worked for a lumber yard for a few years while completing my last degree. Trex or other similar composits contain wood pulp, and although I don't believe termites will be that interested, it does have a tendency to mold pretty bad. They even sell a cleaner specifically for the composite wood decking to remove it. I had this happen personally. I went with 100% PVC decking that was on clearance in the bargain area of a Menards. The store manager made me a great deal since I took it all off his hands. Then I cut it up and burried it 1/2 way into the ground so about 3" is exposed. I also used it for the path between by beds. All in all, I was impressed. The decking was by Royal products I believe.

I use stacked broken concrete, old sidewalk material is nice to use-- it's usually flat on both sides easy to break into usaeable pieces, has a consistant thickness, as it ages it takes on an appearance similar to field stone and tends to stay in place. you can use construction adhesive to hold it in place, or just dry stack it. i've got one wall thats about 2 foot tall-- thats all the more i'll dry stack it, about 40 foot long and about 1 foot deep. i've seen it used as retaining wall material stacked about 12 foot tall. its usually very cheap(=free) and you are recycling. soil tends to wash thru it if it's spaced too far apart, or you can line it with landscaping fabric. seems to last forever
diggerb

When I moved into my house the previous owner had left a gigantic dog house made of leftover cedar fence planks. They made great raised beds stacked two-high with 2x2s in the corners.

Would anyone recommend using laminate wood flooring boards to build my new beds? They're 8" tall and 4 feet wide. I have so much of it that I can triple them up before using them as sides. Is this a good idea? just trying to save money.

I was desperate to find something VERY cheap. I found 1X1 concrete blocks (for patios), but they were still over my budget. On a whim, I stopped at our local Restore (Habitat for Humanity). Browsing the shelves, I came across all sizes and colors of ceramic tile. When I discovered the price was only $.25 (yes, twenty-five cents!!) apiece, I decided to give it a try. I plan to double them up, staggering the tiles on the inside of the bed. Burying them half way up still leaves plenty sticking out of the ground. I will use rebar stakes to reinforce the corners. They are not in the ground yet, and this may be a flop, but the price was right!!