Question
Hello. I live in a small Eastern/Central Idaho town called Arco and am faced with the task of adding greenery downtown. I was wondering if there were any potted trees that would grow in our climate I think on the plant scale thing we are a 3. I am nowhere near an expert in this area as you can tell by my wording. There is not a very large amount of space to add greenery and I am currently working on flowers. However your input would be greatly appreciated!
Thanks!
Heidi

Answer
You are in a USDA zone 4a (Sunset zone 1).  The map is pretty tough to read, as the hills create all sorts of microclimates in your area. If you'd like, I can send you the map I used - I had to overlay your county map onto the USDA state map in Photoshop - but, trust me (or rather the USDA), you are in 4a.

Depending on the container size (I usually deal with 5 ft x 5 ft x 3 ft tall, min. for trees in big pots), there are all sorts of options.  I include a layer of crushed aluminum cans or structural foam in the bottom of the container base, as this lessens the settlement of potting media and if you have to move the thing (trees and dirt can be VERY heavy), you won't max out the forklift/crane.  If you are planting directly in the ground, then never mind the soda cans/foam idea.

Some smaller trees that will survive your zone are: Birch, Catalpa, smaller Maples (Pacific Sunset, Queen Elizabeth, Columnar Maple), Crabapples, Hawthorns, Amur Maple, Serviceberry, Newport Plum (beautifully colored leaves), or Bolleana Poplar (tall & skinny).  You might need to watch the mess on some of these (messy fruit/annoying leaves/twigs, etc.), if it is near foot traffic or cars.

Not just flowers, but I would also add a mix of evergreen/semi-evergreen shrubs, too. ?Barberry, Honeysuckle, Potentilla, Spirea, ground roses.

For winter interest, you may also consider dwarf evergreens, if they do not block store-fronts or intersection sight-lines. Just watch shadows across sidewalks and such(ICE!)  

It all depends on your budget $$$=pretty! I have even harvested wild plants for funding-limited communities; and you know they will grow locally.

Another good source of local plant information/election/ideas is the Idaho Master Gardener Program, which divides ID into regions with expert local help:

http://www.ag.uidaho.edu/mg/counties.htm

Beyond just making the downtown look attractive, the Idaho University Extension has a great Economic Leadership Program, with helps with developing small-town tourism & other economic ideas:

http://www.extension.uidaho.edu/community.asp

Hope it helps in making your community more beautiful! -Marc