Grow pots - size and recomendations

I am looking to grow some different deciduous trees in grow pots. My soil in my area is extremely heavy and full of clay. I tried raised beds and these are just too expensive and time consuming to build. I also have a limited area to build the raised beds. I was thinking about going with grow pots. I tried some Anderson flats and they seem to work ok. But when you have smaller trees you really need to watch the water. I have moved to a completely inorganic soil mix (turface and pumice). I would like to see your comments regarding grow pot types, sizes and if they work or not.

Material I want to grow are elms and maples, mostly small starter material less than ½” trunk size. I would appreciate your guidance so I do not waste my time and effort if this has already been explored.

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I size the pot to the tree. For 1/2 in (1.3 cm) trunk maples and elms I would use a pot that is 8 to 10 in (20 to 25 cm) or so wide and 1.5 to 2 in ( 3.5 to 5 cm) deep. I either make wooden boxes with a coarse screen (1/4 in - 6 mm) hardware cloth bottom (think of a min Anderson flat), or buy the heavy plastic saucers for under pots and put several 1 in diameter drain holes in them. Both work quite well in promoting a good flat root base. I feel I get slightly stronger growth from the saucers - most likely because they hold the moisture better on hot days - and need to repot every 2 to 3 years due to circling roots. The boxes end up with less circling and need to be repotted less frequently. As the trees get bigger, I increase the pot size.

I buy all kinds of plastic containers from the Dollar Store. Make sure to check the pet section which often has dog bowls that can be used as growing containers. Just need to drill holes.

For heavy stuff I line soda pop boxes (plastic "trays" used to carry 2 litre bottles), old fashioned milk cartons and 5 gallon dry wall compound buckets, cut down to the proper height. I line the boxes with landscape fabric or window screen. Styrofoam coolers make good grow boxes.

Some brands of kitty litter and dishwashing soap come in heavy plastic containers. The plastic containers can easily be cut down with a hack saw.

I collect this useful junk from here and there.

I have used pond baskets very successfully. They are available in many sizes from 4" to ver big ones. Planting in baskets has the added benefit of roots being air pruned and the root mass becoming more fibrous.

A gardendori from last spring:


IMG_1992 by Arihato, on Flickr