What problems might we encounter in raising Colorado blue spruce trees in containers?
We are raising Colorado blue spruce trees in containers to a 4' height. Can I feed them nutrients to produce a silvery blue color? We are burying the containers in the ground and insulating with straw. What problems might we encounter? We are in Durango.
Denver County Colorado
Colorado spruce seedlings will vary in needle color. Each seedling's slightly different genetic makeup will determine needle color.
A fertilizer cannot be used to produce a uniform silvery blue needle color on all of these seedlings. However, the newest growth from buds in May-June will be more silvery-blue; this color fades to the needle color of the entire tree by August.
The only way to guarantee a more uniform silvery blue needle color on all your Colorado spruces is to grow grafted or budded seedlings of a named cultivar, such as 'Hoopsii' or 'Fat Albert'.
I'm assuming that you are burying containers in the ground for winter only, and that the insulation of straw is a mulch used on top of the rootball in each container.
Try not to let wet straw stack up against the trunk of the tree. Straw may serve as a nesting site for voles or field mice. They could gnaw on and damage trunks/stems during winter.
It's possible that your container soil mix, if light and well-drained, may hold too much water if the soil in which you bury containers has very different texture and drainage.
You'll want to water containers during dry warm snowless periods in winter.
another potential problem may be associated with water quality - irrigation water that is saline (salty) to moderately saline may damage roots of your spruces.
If you've been irrigating many other plants over several years without any problems, water quality isn't a factor.