How big are the trees and what kind of fruit are you talking about?
If they're going to have any substantial size, I would go with a relatively heavy medium like gravel or river rock.
Are you going to flood the 5 gallon bucket from a seperate reservoir? why layer them together; to make them easily prunable?

I have a key lime tree in a 5-gallon bucket right now. It's not hydro, but fwiw I think the 5-gallon is too small. I went from a 2 gallon to a 5 and it loved it. Now I'm getting yellowing leaves and I think it wants a bigger pot. If you want to never have to re-pot your tree, you might look for a bigger container, like a trash can or small barrel. If it's heavy and you want it to be mobile, you can strap it to a dolly/hand truck.

how about a missouri gravel bed style medium with pea gravel and calcined clay? i have been using that mix to hold landscape materials and it offers quite a bit of stability. I use a 2:1 gravel:calcined clay (turface) ratio. The calcined clay fraction helps considerably with water retention.

Sorry for the slow response I have been traveling for the holidays.
My plan is to grow a variety of fully dwarfed trees, with possibly some semi-dwarfed. I would be growing citrus, apples, pears, and some stone fruit like mangoes and plums. I would be pumping to the buckets from a separate reservoir. The stacked buckets I have gathered are to allow air circulation, hold the medium together by flooding them together in the bucket, and it keeps the medium from clogging the pump. If they will also make the tree roots easily prune able that would be a bonus.
I like the idea of never potting up, but to fill a trashcan with medium would be very expensive. I was hoping the excess of nutrients that causes smaller root masses in hydroponics would mean hydro trees would not have to be potted up or even pruned. Does anyone have insight on this?
Finally thanks for the medium suggestions I will check into that mix as well as just gravel.

Normally, root mass is a function of plant size. In hydroponics, your plants won't really have a smaller root mass. You're just able to keep said mass all together since you're giving them food directly. Thus the roots don't have to go out in search of food (or water) The pot inside a pot is not really relevant to EnF systems as far as providing air to the roots. basically, during the drain, or flo, part of the cycle air is pulled down into the medium where the water has departed. That is how EnF aerates the medium.
As far as container size, I doubt a 5 gallon bucket will be adequate for the life of the tree. a 5 gallon bucket full of medium might support one (maybe two) tomato plants when full sized and fruiting. So unless the trees are very small, it is just not big enough. The dwarf apple and orange trees I have seen are just not that small.
Through the years, I've seen people come here looking to grow a variety of long term plants in hydroponics. I say this to you as I've said to them, without any intended disrespect or arrogance, but those types of plants are best suited to be stuck in the ground. hydroponics requires periodic regular attention and most people don't really want to maintain that kind of attention indefinitely. That is why it is best to grow single crop plants. That way when you're tired of tending to them and/or they've played out, you can simply kill off the plants and take a break. with a long term plant, like a tree, you don't really have that option.
Now maybe your personality isn't like that. I would suggest you grow something smaller for a spell in a hydroponic system to see if you're really inclined to maintain an indefinite routine for a hydro system. Perhaps 6 to 8 peace lilies. That way when you get tired of tending to them you can simply pot them and give to friends.

I had entioned this earlier hopeing to get some discussion going on the thought of over wintering trees hydroponicly.

the only way you are going to grow a tree without having to maintain the roots ever would be to plant them in the ground. You will be able to maintain them in a hydro medium for a long time, but eventually you will have to deal with too many perennial roots versus feeder roots. I suggest you check out tapla's post over in the container forum about growing trees in containers. He is an experienced bonsai grower and bonsai culture is essentially a to waste hydro culture. He breaks down root maintenance very well.

Dwarf trees are a huge misnomer. A dwarf citrus grown in the ground will still grow to be 12 feet tall. It will just do it more slowly than a standard rootstock. Pruning both the roots and top growth will be critical to maintain the trees at the size you want.

5 gallon containers will not be sufficient unless you plan on essentially treating them like bonsai. They will work for a while if you start with 1 gallon dwarfing stock though. I would plan on something bigger for stability alone.

Grizzman you got me. I have been known to drop a hobby now and then.
Anyway this information is just me beginning to put an idea together for the future. Last season was my first hydro grow. I built an aeroponic system where I grew a blueberry, a bush cherry, and some raspberry plants. This season I plan to add an ebb and flow system using a concrete mixing pan to grow strawberries. I probably would let the peace lilies die, but that's only because they don't provide delicious fruit. Anyway this tree project is a couple years in the making, and from all the information you all provided I can see it won't be as easy as I had hoped. But hey that's half the fun. I'll check out that tree container forum and see if I can come up with any more questions âº. Again thanks for the concern and the help.

It doesn't have to be hard. I just wouldn't use a recirculating system. I would just dump pea gravel and turface in a 15 gallon pot and fertigate to waste. You can collect that waste water, readjust nutrients, and reuse. Or just dump it in the yard. Then every three or four years, pop the tree out of the pot, whack the roots hard, and repot in the same pot with new media. You would prune the top hard at the same time.

Trees in containers

Check them out at There is a new Ebb & Flow system design that might solve your problem. The system is called âÂÂOxygen PotsâÂÂ. They use a Ebb & Flow design but they also utilize fabric pots. These are custom made fabric pots specifically to fit in the Oxygen Pots Ebb & Flow 5 gallons. I know the tree industry uses fabric pots more then they use plastic pots so they donâÂÂt have to transplant as often. Tree growers also use fabric pots because trees grow bigger, healthier and faster. Air prunes the roots automatically and it also feeds the roots additional Co2. All these reasons are why you can keep a tree in a 5 gallon Ebb & Flow system for long term purposes. I also recommend you use Hydroton with your trees. Take it from someone who tried everything and get an Oxygen Pot system.
P.S. IâÂÂm a good customer of Oxygen Pots and the owner. I was given a 10% discount code for all of May!
CHASE7517H5X
Check them out at http://www.oxygenpotsystems.com/

Here is a link that might be useful: Oxygen Pots

" a 5 gallon bucket full of medium might support one (maybe two) tomato plants when full sized and fruiting"

Most truly drawfing fruit trees are smaller than a large tomato plant.

I'm growing oranges in a 5g pot, and figs in a couple of 6g pots. You'll sacrifice some production (of course) but you'll still get fruit. (mine aren't hydro)