Raised Grow Beds For Bonsai

>help. My question for the medium is, If I use the above ingredients will I
>need to be concerned with installing some type of drainage underneath these
>beds (French drain type) and having to water more often?

I want you to get it out of your head that drainage will be a problem, because it never is, unless the bed is hermetically sealed (and you've not designed it that way, of course). If it were my bed, I'd lay down either permeable landscape cloth ('weed barrier') or just plain black plastic and punch a lot of small holes using a pitchfork or similar object. The idea is the roots will strike downward, hit the barrier, and the go laterally along their way, taking the trunk along with it. What you don't want is any ground soil/bed soil contact, because then pests become more prevalent (along with worms breaking the soil down more quickly) and the trees will just root right into the surrounding soil, ruining one of the great features of the raised bed for bonsai-- the quick development of root flare. Also moles, voles, chipmunks, badgers, wolverines, etc. tunnel in and munch your roots-- annoying!

My favorite soil for beds is actually quite low in inorganic material-- inorganics in bonsai are used for their superior drainage and porosity [Editor's note: please see the article titled Healthy Bonsai From The Ground, Up to learn more about bonsai soils] but that's not needed in a bed because of the massive surface area we're dealing with. The water evaporates out quite quickly. Anyway, my favorite recipe, wrested from the great Peter Adams, is: equal parts spent mushroom compost (sheep manure that's had most of the nitrogen kicked out because it's been used to raise mushrooms), decomposed pine needles (a natural acidifier and source for mycorrhiza) shredded peat, and sand. Not everyone can get their hands on spent mushroom compost, so a suitable replacement is any well-rotted manure (bat guano is awesome, lots of trace elements). This provides an incredibly nutritious, light but moisture retentive soil that will allow the trees to bulk up quickly.

I like your idea of narrow, long beds because that will make tree maintenance much easier, along with weeding. If it were my space, I'd use either one course of cinder blocks or one course of 6x6 railroad ties. I've seen truly enormous azalea being field grown in Japan, and they invariably are in one-course deep cinder block beds filled with Kanuma soil. These are bonsai wannabes with eight to ten inch trunks-- with incredible root flare promoted by

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