Any suggestion on a plant that would grow under spruce trees whose lower branches have died and been removed, something that would grow to a maximum of 15 feet, offer privacy and help shade out weeds? - C -
Leatherleaf viburnum (V. rhytidophylloides 'Alleghany'), Oregon grapeholly (Mahonia aquifolium) and Ural false spirea (Sorbaria sorbifolia) are three shrubs we consider for situations such as yours.
Most of the time, however, when spruces have limbed themselves up so far, the best solution is to remove the spruces and start an entirely new hedge.
If that seems too drastic consider this: Given that the spruces are bare in precisely that area where you need a visual barrier, the trees aren't fulfilling your needs anymore. They no longer provide you privacy, so you are already starting over. By keeping the useless, deteriorating trees in place you accept several handicaps. One, your newcomer plants must deal with competition from the spruces. Two, your choices in plants are limited to understory species. Finally, you're probably hastening the spruces' thinning and death with the root damage you'll inflict as you plant beneath them.
Regarding the picture below: If the purpose of these black spruces was to block the view of the road, cars and house beyond, that objective is no longer being met.
The shrubs in that bed will eventually become a screen 10' tall. Yet their growth would be quicker and foliage more dense if they had open sky above them.
Leatherleaf viburnum (V. x rhytidophylloides) is a fast growing shrub that keeps its leaves a full year in most situations, dropping the old foliage only in extreme winters or as new leaves emerge in spring. Pruned every spring and touched up every summer they can be kept as you see here, just about 6' tall. If left to grow they would reach 12' or more with rounded tops.
The flowers of leatherleaf viburnum are ivory in late spring, with a sour scent. The berries are red ripening to black in late summer and are favored by birds.