Hello FB1- A white oak is very, very beautiful and must have acidic soil, from my understanding, so I am assuming that's what you have. Out here, you can only find them in East Texas (acidic). But the OP said his soil is alkaline. They can be successfully grafted onto a bur oak rootstock, and I'm considering getting one of these (probably the next tree I plant). My hunch is that your microclimate doesn't resemble the OP's at all. A black walnut gives off a toxin harmful to other plants and trees. This effect will likely be more pronounced in SLC. A tulip tree requires a ton of water in the heat and and will drop leaves in mid to late summer, when shade is needed most. A hackberry is very common here and plumb ugly. I hear that a lot. I think all native trees have their uses, but I personally wouldn't plant one in a front yard. A sycamore is a beautiful tree, but with a destructive root system. Any maple that is not native to an acidic soil is going to be shorter lived in an alkaline/droughty soil, and are known to have shallow and greedy roots. Many well established maples (that are not on the list I provided earlier) died recently in the drought of the last few years. here in Texas (10-20 percent, statewide). There is plenty of information on this forum, OP, why smaller is better. Interestingly, small seedlings of gingko (non-named cultivars) may turn out to be female, but aren't as slow as one might think, at least here in Dallas. It's a "must-have" tree, imo. It should be planted where shade isn't needed quickly. It would be real easy for me if I lived in SLC, given the information provided, what trees I would chose. The last thing to think about, and this might not be as important to you, is how responsible is it to plant a tree that wastes resources in the form of irrigation. Costs money, and is a lot more work than a tree that you can simply let go for the most part, and will thrive and be happy, healthy, non-destruvtive, long-lived, and BEAUTIFUL, as well. Never undertstood the fascination with most maples planted where they were never meant to grow. If you don't give them a lot of tlc in that type of environment, they're chlorotic and ugly, imo. All for a few weeks of fall color. You can tell a yankee down here, lol, by the type of maple in his front yard. Best, best wishes, OP, I've exhausted the subject or at least my experience/knowledge on droughty/hot/alkaline microclimates. M This post was edited by Mackel-in-DFW on Wed, May 14, 14 at 9:42

It isn't really necessary to repot and replace soil every two years if the soil mix is properly chosen to begin with. Roof top gardens are a similar situation, and rely on sand as a major component of the soil mix to avoid major drops in planting soil depth. I generally prefer to avoid organic/bark based soil mixes in large planters in favor of using a mix of sand, perlite, and pumice, with 25% maximum coconut coir. This sort of mix, even though it is totally artificial and has little organic/humus content, does not get anaerobic or evaporate over time as a bark based soil mix does. It will require regular fertilizing to maintain plant growth, as there is nothing to hold onto nutrients in such a well aerated planting mix. Repotting can be as simple as removing only the outer 1.5 to 2 inches of soil and applying fresh soil, similar to how bonsai plants are treated, and doesn't necessarily require removing the plant from the container. I'd agree that in general, keeping a small tree in good health in a hot southwest location does require more work than the same plant in the ground, but it isn't difficult if the right plant is selected for the conditions and degree of maintenance to be given. I wouldn't be recommending something like a Japanese Maple for a hot southwest facing wall, as a tree like this can't survive on just twice a week watering in heatwaves, and will most likely get leaf tip burn by mid summer. It would be a much better candidate for an east or north facing wall. Given that the OP wants to only water twice a week, it makes more sense to choose an extra drought tolerant species such as the Olive, or something equally tolerant of heat and drying out. If it is at all possible to provide automatic drip irrigation to these containers, it widens the possible list of potential plants exponentially.

Soil-less is hydroponics. Organics is a scam. Chemical fert is salts. Organics need to be broken down to the same salts that chemical fertilizer is made of before plants will absorb them. i have no problem with organics but it's not better than chemicals. Urine is organic feces is organic dead rotting animals is organic household ammonia is organic anything grown with artificial light, even just sprouted seeds, is not organic. Organic trees can be non organic trees fed organics only for a year. So something like grapefruit that takes 15 months to grow can start growing on chemicals, switched over, and be sold as organic.

coco does not disintegrate, it resist decomposition and last several years.. i have made a quick video showing how airy it is, and it's certainly not "dust" like it's mentioned in that 2 line sentence about the person in that link you posted say it is, and as i've said, coco can be purchased in coarser grade too. i'd imagine mixing the finer grade coco with the coarser coco would make one hell of a mix that will put the 5-1-1 mix to shame and keep so much money in your pocket.. but i think just the normal texture coco is fine, there are plenty of people who use it on thehotpepper forum by itself with amazing results. it does not compact at all despite how hard it is squeezed. very fibrous which is why it does not really need any additives such as perlite, bark, etc..which saves huge amounts of money. the amazing thing about is it has tremendous water holding capacity while still staying light and airy and not suffocating plant roots. there are so many other reasons why it's superior to just about every type of planting media out there. research and very much doubt you'll find many valid negative things about it.