The tree boxes I have experience with, are short lived.

Hi Jim, you're referring to the ones from nurseries, like the picture I have? How short? If we're talking couple of years, then I'm going to pitch them. I'm in southern california and mostly dry here.

snuffles - I think the wire would look awful and not work too well either. I imagine you would have trouble getting it tight enough to hold the boxes together. I would suggest putting a piece of 2" x 2" wood down each corner on the inside and then screw them in place from the outside. That is through the external vertical edges, through the horizontal slats and into the 2" x 2" pieces - 3" screws every 6 inches should do the trick.

Plumbing section in HD will have rolls of metal straps used to hold pipes. You can cut them to size.

The box is huge and with the weight of wet mix the bottom will give up first. If it is cedar or redwood it will last a bit longer but the bottom needs to be thick - at least an inch thick.

I think plywood will fare better than pine since the layers have opposing grain directions. CA might also be better location. Our winters are too harsh for just plain pine wood. Especially the bottom boards. And it will need to be reinforced too with cross braces.

Thanks for all the tips. We're going to try using 2 x 2 on the insides and use thick plastic liners and NO bottom so roots will go directly in the ground which is shallow but very wide. We want to elevate the tree and like the way the box looks.

They are not constructed out of long lasting wood. They are used to change the growth pattern of roots (circular) of trees grown in round containers. There are commercially available liners designed to be used in the nursery planters. The larger a tree grows, the larger container. Is the wood rough sawn? Dark streaks?

Yes, maybe a couple of years.

If you want a wood planter, I recommend redwood, (West Coast). But I understand the difference in cost.

Have you considered using the wooden boxes as cache pots by putting a cheap plastic pot inside them?

Yes the wood is rough swan and has dark streaks and I know there are better wood out there but I mainly want to repurpose these wooden boxes. True that the bottom will be the first to go as experienced with my oak wine barrel planters. That's why we're going to use them without the bottoms, which would also benefit the roots. Yes I've thought about using a plastic pot inside but none are square and as large as the wooden box. We have enough to experiment with so will have a go at it. We don't have as much of an issue with things rotting as much as sun damage. Things left outside tend to stay dry most of the year.

When I built my tree boxes (2' x 2' x 2') I lined them with landscape fabric. I know it is not water tight but I just wanted to keep the wet soil away from the wood. It was purely an experiment to see if the boxes last longer with it.

Yup same reason I'm lining the boxes with these thick black commercially plastic sheeting we have. So did they last longer for you?

I suspect your planter boxes are disposable, used by commercial nursery’s. They may be constructed from beetle killed pine. Pine is not earth contact resistant as is redwood or cedar. Reads you are going forward with this, please research using pine as a planter box.

I don’t think fences are made from pine, so you may have damage from sun. Maybe your research will find a pine preservative.

I don’t understand why you want to plant trees in a box above ground, maybe an attempt of raised boxes?

I repurposed pallets and they had maybe 2 years life. But, it was what I wanted to spend....time vs money.

Good luck.

I can't tell the difference in type of wood but I just googled lumbar companies that make these wooden tree boxes for nurseries and they all say the materials are either cedar or redwood. Yes I mentioned in my comment earlier that we wanted to elevate the trees.

I made mine from cedar. I can't say if they have/will last longer yet as they are only two years old so far.

Im growing trees to sell later and am interested in these to grow trees bigger. So, thats typically what they are for. I. Going to try and build them myself, but dount see why i couldn't just make square boxes, as they are easier to make.