I'm looking to buy a bunch of 10 inch tall spruce trees. Each of them will go into a 5 gallon pail, and the pail will be put into a trench in the ground. Each year i'd add some slow acting fertilizer. The idea of pot below ground is less watering and better temp protection. Is this plan a good one?

It seems to me that those pots are going to severely restrict the root systems of your trees. And I don't think spruce trees need "temperature protection" even if the buckets did provide that, which I don't think they would. I would suggest using a layer of mulch around the seedling trees (not right up against them), which helps prevent the ground from successive freezing/thawing/freezing.

Agreed, and they would be more likely to heave.

Are you just storing them before they go in their final location? I don't understand. Are you thinking of keeping a tree in a pot?

I am trying this too, but for a different reason:

We have a clump of young cedar trees (from 6 to 15 feet in height) serving as a screen. The trees will eventually grow too large and we will have to remove them. I plan to gradually take the larger ones out first and let the smaller ones grow a bit longer. Meanwhile, I hope to establish a new crop of seedlings in place, but without competition from the larger trees' root systems.

So, I have dug holes in the soil around the larger existing cedars. Into those holes I placed 5 gallon pots, each one containing a two year old cedar seedling. These can grow in the pots for a couple of years underneath and in very close proximity to the canopy of the larger existing trees, but without competition because they are isolated within their pots.

Then, in 2 or 3 years (before the root systems of the younger trees get root bound) I will cut down the larger of the cedars. Once that's done, I will expose most of the sides of the 5 gallon plastic pots and slice them down the side walls, removing most of the plastice sides and the bottoms of the pots without disturbing the young cedars' root system. The young cedar can then continue to grow in place, without the set back of being transplanted.

I hope this works. Maybe it would be easier to start from scratch once the older trees are cut?

PK