Question
Hi Marc,

I live in central Minnesota. I can really use your help. Can you give me some suggestions of plants that would grow well in my area that is considered thick deciduous plants and trees?  I would like to use these plants as noise buffer on a 30 foot berm in my backyard that backs up to a heavily used county road.  I am also considering putting up a solid 6 ft. wall of fence on the top of the berm to help with the noise and dust, and to add privacy.  How can I maximize my outcome to achieve my goal?

Answer
You are correct, in that a berm & wall are your BEST bet on lowering sound.  The wall should be concrete, but a thick wooden wall will work too.  The best method for sound attenuation is getting the 搒ound deflector?as close as possible to the point of origin.

Consult your local building officials, as some communities require a permit to construct a wall or plant bushes, sometimes as low as 18-inches tall, at or near a roadway.  They want to make sure you don抰 block the traffic's ability to see obstacles, like kids in a cross-walk, etc, and that you actually are building it on YOUR side of the right-of-way.

As to plant selection and design ideas:

http://www.sustland.umn.edu/plant/

This excellent website, created by the University of Minnesota Agriculture Extension, discusses basic and advanced landscape design principles.  I could suggest a number of plants, but I think do a little of searching for yourself.  The website has a basic plant-search engine that may help you in your endevors:

http://www.sustland.umn.edu/plant/search.asp

Your factors are:

Plant type: "Evergreen tree" or "Evergreen shrub"
Use: "Screen" or "Screen Plant" for your tree search (but not the shrub search, as no shrubs will come up)
Hardiness Zone: 3 **
**Minneapolis/St. Paul, Minnesota is a 4a, International Falls, Minnesota is a 3a.  Check your zone here, by zip code:  http://www.arborday.org/treeinfo/zonelookup.cfm

I put in a "3" for your zone (not knowing exactly where you live in Minnesota), and came up with several prospective plants:
Norway Spruce, Scotch Pine & Canadian Hemlock - all good, thick screening trees.  In the evergreen shrub department, there are a number of Juniper and dwarf Fir that may work, plus Mugo Pine & Arborvitae.

I know you asked for  "thick" deciduous or semi-deciduous plants, but a search though this nifty site only turned up 8 possible prosepects. There are not as many deciduous as evergreen plants to choose from.  I think it looks nice to mix decidous & evergreen together, in my opinion.

Check with your local nursery for availability in your area, too.  Plants like Barberry (hardy to zone 4) are readily available, but rare native plants can be a challenge to find.

Enjoy the hunt & good luck!  ~Marc