Ask Mr. Smarty Plants

Since you are asking about a barrier, I am assuming that you want evergreen plants. I will give you a few suggestions including both conifers and broad-leafed plants.

The two broad-leafed plants are deciduous, but they hold on to their leaves until late fall.

Saskatoon Service berry Amelanchier alnifolia (Saskatoon serviceberry)  is an erect shrub 3-18 ft tall. Produces small blue berries in early summer, and fall leaf color is orange.

Mountain Mahogany Cercocarpus montanus (alderleaf mountain mahogany)  is an 8-20 ft shrub with almost evergreen leaves. 

The three conifers listed usually grow taller than the height you indicated, but there are dwarf cultivars that can be had.

 Picea glauca (white spruce)  has several cultivars that are termed 'dwarf' that might work (e.g., 'Conica' or "Dwarf Alberta Spruce", 'Pixie' and 'Rainbow's End').   More images

Rocky Mountain Juniper Juniperus scopulorum (Rocky Mountain juniper)  Mature size is from 30-40 ft. high with a spread of 3-15 ft., but has cultivars that are shorter (e.g., 'Welchii' and 'Medora').  More images

Picea pungens (blue spruce) can grow from 50-100 ft tall, but it is usually shorter in cultivation. There are several dwarf cultivars.  More images

You can find more possibilities by going to the EXPLORE PLANTS menu and select Recommended Species. Click  on Idaho on the map and you will get a list of 111 commercially available native plant species suitable for planned landscapes in Idaho. Go to the NARROW YOUR SEARCH box and make the following selections: Idaho under State, Shrub under Habit, Perrenial under Duration, Sun under Light revquirement,and dry underSoil. Then click the "Narrow Your Search" button. Your list has shrunk to 29 shrubs. You can then repeat the process and select "Tree" under Habit.

Once you have found some plants that interest you, go to our National Suppliers Directory, type in your state, and you will get a list of  businesses that sell native plants or seeds and provide professional landscape or consulting services in Idaho.