Soil for large grow boxes

[swatchpost]

Hello All—

I was planning on buying a couple of large grow boxes for some trees to thicken trunks for 5 -10 years. What type of soil should I use? Regular well-draining bonsai soil fitting to the species? Or something more organic like one would find if you just planted the trees in the ground?

What do you all recommend? I was thinking about using something like this photo with proper drainage holes in the bottom. The one they actually have at my local garden store is shorter and squattier and lends itself better to bonsai.

 

[Mikecheck123]

It's a common myth, but a bigger pot doesn't make it grow faster. It's better to keep uppotting over time.

Also, filling something like that with bonsai soil would be a very expensive proposition.

 

[ShadyStump]

It's a common myth, but a bigger pot doesn't make it grow faster.

No, but a smaller pot will make them grow slower.

I do agree, though, that it would be expensive and unnecessary to use straight bonsai mix of some sort. The deeper the pot the more efficiently it drains, and the larger the volume the more water it can retain (roughly speaking) so you have allot more leeway in what you use. Depending on what you'll be planting in the pot, you could get away with a standard potting or nursery starter mix, maybe mix some extra perlite or lava rock or the like in to help with drainage and development of the fine roots.

 

[erich_raudebaugh]

I've done this before, with a 35 gallon steel tub. Way more soil than you need, but the reason was because I was living on a floating home and didn't want the tree blowing over or waves knocking it over.

I used lava rock (scoria) in the bottom quarter or third to essentially make the tub shallower. The other soil was large particles of pumice, about 3/8", mixed with a bit of organic compost, lava, and local diatomaceous earth (very hard, from Washington). It would have been fine in 100% pumice, but I didn't want to water so much.

This was a trident I've been developing with sacrifice branches and leader chops. In 4 years, roots filled the tub including the lava rock, which kinda served as ballast.

The trouble with this method is that there are a massive amount of roots to tame.

There would be no point unless you have a large tree, and a grow box will probably produce the same results.

 

[Wulfskaar]

Another thing to consider is using organic components in the soil. I've read that bonsai artists in TX use a little more organic material in order to retain more moisture during the hot season, which can be long in TX.

 

[ShadyStump]

Stopped by the local thrift shop after work today looking for a desk lamp. Passing by a shelf of reed and wicker baskets I noticed there were a couple of rather large ones, and had the thought of maybe something like that would make a decent grow box for a season or two if they don't rot out too fast. Has anyone experimented with this idea?

 

[Dav4]

Stopped by the local thrift shop after work today looking for a desk lamp. Passing by a shelf of reed and wicker baskets I noticed there were a couple of rather large ones, and had the thought of maybe something like that would make a decent grow box for a season or two if they don't rot out too fast. Has anyone experimented with this idea?

A good grow box will remain structurally sound for at least 2 or 3 seasons, and preferably more. I've never tried them, but I suspect reed or wicker containers wouldn't be strong enough to keep the soil from markedly shifting every time it was picked up/moved which would potentially damage new roots, and the constant moisture would cause them to fail quickly. I've got grow boxes made from pressure treated decking... probably cost less then 10 bucks to make... that have been in constant service for 4-5 years and are still going strong.

 

[swatchpost]

I also saw that American Bonsai has some grow boxes with mesh bottoms. Pretty nice. They'd last a lot longer and you could fill the whole thing with bonsai soil, probably.

 

[Firstflush]

For your needs I would use 3 to 1 cactus mix to potting soil (high quality bagged) and then add a coarse bag of perlite equal the amount of 1/4 of the entire mix. Here in deserty CA I find cactus mix has plenty of water absorption for potted plants.

 

[Shogun610]

I would use plastic colanders on the ground with bonsai soil substrates, or an Anderson flat or even a grow bag. You get the growth of growing in the ground , but better control of the roots. For colanders , you can also but they into larger colanders for extra root growth in case that space is confined.

 

[swatchpost]

Great ideas, everyone. Thanks so much for your thoughts and replies! Gosh, I never considered using a colander in the ground. That's pretty brilliant!