Hey, Bill!

I'm a real novice, so let that be a caveat!
However, I think your growing boxes should be deeper. I'd go at least 8 inches deep, maybe deeper for something like a maple (14 x 14 x 14 inches?). If your goal is to keep the roots nice and shallow for eventual bonsai pots, you might consider growing over a tile in these grow-boxes. I've never tried this, though, so I can't say how well it would serve you.

I think Dax (Gardener365) posted something about a growing box not too long ago....for Japanese maples possibly.

Josh

Nevermind!
It wasn't that deep after all!

Link attached.

Here is a link that might be useful: Dax's first

I made one, 14" x 14" x 3 1/2 deep. This size seems to be perfect. I gave it a quick slopy coat of polyeurthane, just so it doesnt rot out after one use.
Ill tell you what, a box that size takes almost a full bag of profile and half of my bag of aquarium gravel to fill. I think Ill recycle my soil on this one.

I goal here is to get the roots growing flat, so thats why you dont want alot of depth. Its getting trained roots for a pot. Not alot of info out there on grow boxes.

Thanks for the posts greenman.

Although I grew and still grow most of my trees on in the ground, I did have occasion to build some 'training' boxes. The best material I found was called JetNet, it's the same material they make those milky white cutting boards and resturant cutting surfaces out of. The stuff I got was 1/2" thick. It's easy to cut and drill, can actually be threaded (holes) but I put mine together with stainless steel screws. They had a removable bottom with large drain holes (covered with wire just like a bonsai pot). The boxes were from 4-5" deep.

Since I worked larger trees mine were 14-16" by 12-14".

I'd use a thicker piece, 3/4 or 1" square for the legs. Extending across the bottom of the box it supported the bottom. This material will last forever...the last few I gave away were about 10 years old.

I've been building my grow boxes in various sizes, depending on the type of tree and condition of roots. Generally, none of my boxes is more than 6" deep...although for smaller trees I see no reason not to make smaller/shallower training boxes. I use untreated cedar boards to build mine as they are quite resistant to rot, and not expensive at all. I've also used the cedar planks on which we grill salmon, which are reasonably cheap, and already cut to almost the perfect dimensions (usually about 6" wide by 12 - 16" long). I do need to cut these but there is less of this than buying the long cedar boards from a lumber outlet. I like the smell and look of the cedar as it ages, and it seems to enhance the appearance of the trees as they develop. In the bottom of the boxes, I space pieces of cedar with gaps, over which I nail plastic mesh for drainage. The mesh I think is used in embroidery, and can be found at most craft supply shops. Around the perimeter at the top of the boxes, I usually put in some tiny eye screws - these are great for securing branches using guy wire, which reduce the risks of scarring associated with the traditional wire-wrapping techniques (but I still use that method to some extent).

I hope this helps - if you want to see what the boxes look like, please e-mail me and I can send you photos of some of my trees growing in them.

Good luck!

The Cedar is actually a good idea (but will rot). I have used Cedar chips in soil mix to keep a lot of pests away, it works for many of them.

The problem with the (plastic) mesh is that roots will grow through it over time. If you use galvanized screen, 1/8th" holes, the roots of most trees won't go anywhere near it.

I grew partial to the Jet Net because it will never rot. It's also some pretty tough stuff.

I'm not familiar with JetNet - it sounds like it's plastic...is this correct? I know the cedar will rot, but it will also take a long time and if it lasts through the time the tree spends in the box, then I'm happy with that. I can always make more boxes. I have heard of people using all sorts of things for grow boxes, including the plastic bins for washing dishes. The main reason I went with the cedar boxes, is the appearance. I suppose that if you wanted the boxes to last a long, long time, then you could use some type of plant-friendly wood preservative on the box before you use it. I've seen cedar planters sold, which must have had something applied to them. These are not really suitable for bonsai cultivation as they're pretty deep.

The galvanized screen is a good idea - in fact, it seems to me that I'd come across some info online about a training box made with screen walls. These were intended to be used as a step between the tree's residence in a grow box and the eventual bonsai pot. Apparently what happens is that the roots grow to the edge of the box, but once they reach the light they stop. This causes a network of many fine roots to form. I may try something like this in the future.

As I posted above it's the material that cutting boards are made of as well as large cutting surfaces used in restruants. It can be be worked with common woodoworking tools and even drilled and threaded. I used the 1/2" thick material. It's somewhat flexible as well as strong as hell.

Most of mine had 2 large drain holes like a normal Bonsai pot, the 'feet' were put across the bottoms so that the bottom rested on them. I made the bottoms removable and when it was time to pot the plant just put a few bricks under the bottom and push the sides down.

hi, can anyone tell me where to look for jet net.I have searched and have not found a place to purchase.

C'mon guys - that stuff (high density polyurethane, aka sani-lite et. al.) in 1/2" thickness will retail for >$15/sq ft. It's extremely cost prohibitive and an overkill. It's hard to beat wood or a wood/screen combination. It's an advantage to use something that breathes - like terra-cotta bulb pans or wood boxes. If you're going to use the HDPE, you might as well saw off a nursery container.

{{gwi:4800}}

You can get up to 3 years out of a pine/spruce/fir box & 5-10 years out of cedar.

Al

Good to hear 3 years on pine. I went cheap and being my first go now wish I had spent the extra money on cedar. I have no doubt my pine boxes will last at least the three years, they just discolor real quick. Other things I have noticed:
Use galvanized screws, dry wall screws just bleed their color down the wood and will rust.
If you use pine you might want to coat with something or at least glue the edges. Untreated pine will warp after the first few rains and even glued joints will break but if your going to spend the time making them, go for a four year box.
They don't need to be very deep. Unless you are substantially growing you are trying to train the roots out, not down. It is tempting to build the box deeper but they take alot more dirt, get alot heavier, and then you have more roots to remove and probably even another year of training at the shallower depth.
Otherwise every thing I considered to make mine came from the net.

Well...I bought either 'used' cutting surfaces/counter-tops from used restruant suppliers also found a place in Pittsburgh that sold scrap Jet Net material. The material was cheaper than wood of any kind and 'forever' as far as lasting. I also used self-tapping stainless screws for assembling them.

Mmhmm - and how many who go out looking for used cutting board material will be successful @ finding the product to begin with, then in a quantity that would allow them to build boxes from it, then at a price reasonable enough that it was affordable? I come up with far closer to a goose egg than a 1% chance. Besides, like I said - why go to the trouble of building a plastic box when you can simply take a table saw to a nursery container & make it as shallow as you wish? Materials that allow gas exchange (wood, terra cotta, pond baskets, colanders from the dollar store) in the rhizosphere (root zone) should be much preferred over plastic sheet.

Al

Mmhmm...let's see...I'm not as negative or as highly technical as you seem to be. I just found the stuff and did it, it worked and they lasted, made a good transition between the ground and a final pot. Much sturdier than a cut down nursery container and I never had a problem with a tree in one of them.

However, it was only a suggestion in here, because they were cheap and worked.

Bob

I'm only negative to the degree that I don't want to see these guys out chasing their tail looking for a product the astronomical odds are they will never find at a price even close to reasonable (for a grow box); and I could easily offer a couple of links illustrating clearly that you're no stranger to negativity, so please .....

I never said you couldn't make it work or that you should expect problems, only that there are products that work much better at a fraction of the cost they would likely incur to duplicate what you're using.

BTW - since when is a nursery container not sturdy enough to rear woody material in. ;o) With that news, I suppose I'm going to have to repot another extra 100 plants come spring? ;o( Another aside: Since the material you suggested has no UV inhibitors in it (cutting boards & counter tops need no protection from the sun's harmful rays), it WON'T last forever. It will yellow & become brittle within approximately the same time frame that cedar deteriorates to an unusable condition.

Take care.

Al

It was a fregging suggestion anyway!
I guess they could also make their own choices about 'chasing their tails'?

BTW: The first Jet Net box I made was over 10 years old when I gave it and the tree in it away to a friend. It was still in very good condition--I had replaced the original screws with stainless self-tapping ones.

The last used cutting surface I remember buying was 1/2 inch material, 4' X 6' and made 4 nice big boxes...$30.

Now that they have solid information and know how badly the odds are stacked against a favorable outcome for their efforts, they can decide. Chasing around, looking for used cutting board material large enough and within budgetary constraints to make grow boxes from isn't my idea of how I'd like to spend my free time. I took a poll - 99.99% of those surveyed agree. ;o)

You: Eat at Joe's. It's the best restaurant in town. I eat there all the time.
Who you're talking to: Cool - sounds great!
Me, butting in: Ummm - Joe's doesn't even have prices on the menu because everything is $200/plate & up. Oh - and by the way, it's black tie only. (NOW they probably have the info they need to decide whether they want to try Joe's.)
Who you were talking to: Oops!

Al

I like used wood for cuttings, even clematis boxes. Very cheep. But using cutting boards that can be carved into flat containers with the use of clay sounds interesting.
Paul

Sorry
I meant clementine boxes.
Paul