The best trees are the ones growing natively in your area. Once established they require ZERO care except in the most severe droughts. But some are understory trees at least when young meaning they start out under a "nurse" tree that provides some shade, increased humidity and wind protection. When you take a tree out of the pot and plant it out by its lonesome that can be a problem. I am not sure what you can do about that beyond possibly erecting a temporary western shade structure or planting a tiered screen of groundcover, shrubs, trees. If you buy trees at a nursery you often find them under a shade tree. They are conditioned to that environment and need to be hardened off by gradually increasing their sun exposure over a period of 2 weeks before transplanting. Secondly, they are growing in a pot, then find themselves in the ground. Two very different soil conditions. In a container the soil is rapidly draining and the nursery fertilizes it periodically to replace the nutrients that are washed out. Controlled waterings. While your area is also rapidly draining it likely is poor in carbon and maybe nitrogen. It may be high in salt and pH. "were brittle and dead within 3 months (even though they received ample water). And I don't think they got over watered -- especially considering that they are planted in very sandy soil." Sounds like under watering to me or root rot from over watering or lack of root development (not likely since they haven't blown over---unless you stake them). Could also be root disease like nematodes. Again natives are resistant to such things. How did you determine "ample?" "The ones that are alive are brown and with excessive foliage having dyed off. I assumed it was the cold, but maybe not. I planted some in the summer and the exact same thing happened (one was dead before the cold ever set in and the others had most its foliage turn brittle)." Sure sounds like dessication or lack of water uptake/availability to me. Young plants need to be watered frequently to a depth of 3 feet until roots are established. Sandy soil so you must water frequently, but most water applied goes straight down fast and doesn't spread out. Additionally at 5,500 feet evaporation is increased as is solar intensity. Add dry winds. Is there a surface mulch? A rock mulch might help to raise surface temp, cut evaporation and block competing weeds. What kind of trees natively grow in the area? What kind of successful non-natives do you see and how are they cared for? Hopefully your trees were planted at an appropriate depth in the pot and then in the ground? Hopefully the roots weren't circling the pot at the time of planting or were cut or straitened out? I would carefully excavate the dead ones and examine the roots for formation, planting depth and galls/knots. As I linked your local Co. Exchange agent or MGs (and the incredible Arboreum) are more familiar with your situation and can advise and diagnose. A certified arborist landscaper may prove cheaper in the long run to plan and plant. This post was edited by Fascist_Nation on Thu, Apr 3, 14 at 14:57

At about 48 degrees North latitude, I'm about 8 degrees further north than Denver. I am at 2,000 feet elevation. Since 1 degrees of latitude = 69 miles or 364,320 feet), I am 2,914,560 feet north and at an equivalent elevation of 5,643 feet (2914560/800 = 3643 + 2000 = 5643). What was the question? Oh! When I built my 180 square foot backyard greenhouse 20 years ago it was with the intention of running it thru the winter months. The greenhouse could be called by some, a "sunshed." It has an insulated north wall and roof, half of both the east and west wall are insulated. The south wall is UV-resistant plastic film set at an angle to best admit mid-winter sunlight. I had a natural gas ceiling heater installed. This kind of heater is often found in heated garages. Before I did this, I checked with the engineers at the local utility and talked about solar-gain. They told me that heating costs should average about $20/month thru the winter. That was 20 years ago. Plans change. I have never run the heater thru the winter and don't know if the engineers' estimate was accurate or not. It doesn't seem to burn much gas during March and April when I do run the furnace. I forget what the angle of the south wall is. It would be different for a place 8 degrees south of here. Your hours of winter sun in Colorado are a good deal greater than here not only because of more hours of daylight but because of greater chance of cloudless days thru the winter. I purchased 6, double-tube, 8' fluorescent fixtures for supplemental lighting. You may not feel that this is necessary. Somewhere, I found information about sunlight at various locations throughout the US. The solar power advocates use that info to assess the value of solar power. Sunlight is very important to someone who has a greenhouse. I will see if I can come across that again. One thing I learned is that this area is abysmal in this regard. Colorado fairs better. Nevertheless, leaving aside ideas about heat sinks etc., etc. - greenhouse glazing of any sort has little insulation value. And yet, sunlight cannot enter the greenhouse at a high angle nor from the north during the winter months. Maybe there will be more thoughts later. The math may have sprained a brain cell, for no good apparent purpose. Steve

Your higher elevation than the valley means you will get a wider swing in temperatures during the day--so it may be 75 during the day and freeze at night when it doesn't freeze in the valleys. This makes the spring and fall a riskier time and likely a shorter growing season because of the wider daily temperature swings. At the same time, being higher up than the surrounding valleys, the winter lows and summer highs will probably be milder than in the lower elevations. Not sure how all this translates into gardening selections, other than select trees that are late bloomers and/or plant them on a north facing slope where they will come out of dormancy later in the spring. Ripening times will be a little later than in the valleys due to the lower heat units at your elevation, and you will need to cover your tomatoes a bit earlier than they do in the valleys in the fall.

Posted by ddsack z3MN (My Page) on Tue, Jul 15, 14 at 9:59 The internet can be great if you use critical thinking skills and can be selective in what advice might work in your location, and most of that comes from experience. So many forget that what works great in the south, might not work in the north or in high altitude gardening %%%%%%%%%%%%%%%%% Well said. You cannot take any article, You Tube video, blog etc at its face value. They can be a source of confusion sometimes. I started learning the fundamentals about soil chemistry ( pH, nutrients) , Soil physics ( water drainage, retention), micro herds/soil web, . Then start learning about plants in more specifics. What one can learn is never ending. I learn something almost everyday.