Question
I live in Milwaukee,WI, very close to lake Michigan (zone 5b).  I planted a trio of skyrocket junipers 10 years ago in a row (east to west) with 9 feet between each tree.  They are on the north side of my side yard, and share a narrow planting bed with only Siberian iris.  The westernmost tree is located at the drip line of a 90 year old Norway maple that is about 50ft tall.  I have the maple pruned every 3 years to allow light penetration but it's still a huge tree that casts a big shadow.  The trees are all 15ft tall.  They are parallel to a walkway and used to get quite pounded by the snowblower before I started wrappiing them two winters ago. The easternmost one (gets the most direct sun and is furthest away from the maple) is quite healthy looking and needs to be pruned. The middle tree is thinner with less robust growth and more dead interior branches apparent. The last tree is almost see through and especially bad on the west side. they are on a sprinkler zone that only waters this bed and I do not believe that watering is a problem. I do not fertilize.  I recognize that sunlight is likely my problem and not something I can control. My questions are:  Other than competition for water, light etc., is there anything about the maple that affects the juniper?  Is there anything I can do to help these three trees grow more uniformly?  Since the westernmost tree is already pretty bare looking, is tree anything I can do to help it regenerate?  Finally, if this is a lost cause, do you have any ideas on how I could get the desired effect (3 tall thin sentinels in a row) and have more uniform growth under these conditions?

Answer
I agree the sunlight is the problem. These do best planted in full sun, it is, however, able to handle small amounts of shade throughout the day.Growth rate, and foliage density will both suffer when planted in shady locations.   The maple is not effecting the juniper except by the shade. And there is not really any thing that can be done to the juniper to increase the growth. Sorry just does not seem like a good place for the juniper to grow.