Some individuals consider shady sites to be problem areas in the home landscape. However, shady areas actually provide opportunities for home gardeners. Wise plant selection can turn a shady site into an attractive landscape area. A number of trees and shrubs can be successfully grown in partial shade. (Partially shaded sites receive 3 to 4 hours of direct sun, but are in shade the rest of the day.)
Below is a list and brief description of trees and shrubs adapted to partial shade.
Serviceberries (Amelanchier spp.) are native to Iowa and are often found in open areas in woodlands. Other common names include Juneberry, shadbush, or sarvis-tree. Serviceberries are large, multi-stemmed shrubs or small trees that reach a height of 10 to 25 feet. Ornamental characteristics include white flowers in mid to late April and colorful fall foliage. Fall foliage varies from yellow to orange to red. (Fall color is generally best in full sun.) Serviceberries also produce small, berry-like fruit which usually ripen in June, hence the common name Juneberry. The ripe fruit are excellent in pies and muffins. The birds also love the fruit and usually devour most of the fruit before they can be picked. Excellent cultivars for the home landscape include 'Autumn Brilliance,' 'Princess Diana,' 'Cumulus,' and 'Strata.'
American hornbeam (Carpinus caroliniana) and ironwood (Ostrya virginiana), also known as American hophornbeam, are slow growing, native trees that should be used more in the home landscape. The mature heights of the American hornbeam and ironwood are 20 to 25 feet and 25 to 40 feet, respectively. Their use in the landscape has been limited by the fact that both are somewhat difficult to transplant. However, once established they develop into small, attractive trees.
The eastern redbud (Cercis canadensis) is native to much of the eastern United States, including southern Iowa. It reaches a height of 20 to 25 feet. Redbuds are cherished for their pinkish-purple flowers that appear in late April or early May. (There are also a small number of white flowering cultivars.) Mature trees possess a handsome flat-topped to rounded appearance. When purchasing a redbud, select a tree grown from a northern seed source. Redbuds grown from a northern seed source are more likely to be cold hardy in Iowa. They perform best in moist, well-drained soils.
The pagoda dogwood (Cornus alternifolia) is a large shrub or small tree. Its mature height and spread is 15 to 25 feet. Ornamental characteristics include a horizontal branching habit, yellowish white flowers in late spring, and reddish purple fall foliage. The pagoda dogwood requires a cool site and moist, well-drained soils. Protected sites and eastern exposures are generally the best planting sites.
Another large shrub or small tree is common witchhazel (Hamamelis virginiana). Its mature height is 12 to 15 feet. The flowering habit of common witchhazel is unique. It blooms in the fall (October to December). The yellow, strap-like petals unfold on warm days and curl up on cold days. In fall, the leaves turn a bright yellow. Common witchhazel develops a rounded, open habit in shady sites, but has a more dense, fuller habit in full sun.
Several deciduous shrubs also do well in partial shade. Gray dogwood (Cornus racemosa) is our most common native dogwood. It is an adaptable shrub which tolerates wet or dry soils, full shade or sun. Gray dogwood reaches a height of 8 to 10 feet. It produces whitish flowers in late spring which are followed by small white berries. The use of gray dogwood in the home landscape is limited somewhat by its suckering habit.
Another shade tolerant, native shrub is the arrowwood viburnum (Viburnum dentatum). It is an adaptable shrub which grows well in sun or shade and tolerates most soils. Arrowwood viburnum grows about 6 to 8 feet tall. Plants produce creamy white flowers in spring followed by blue fruit in the fall.
Alpine currant (Ribes alpinum) is an extremely hardy shrub. Its mature height is 3 to 6 feet. Alpine currant is one of the first shrubs to leaf out in the spring. It tolerates pruning well and makes an excellent formal hedge.
Other shade tolerant deciduous shrubs include
- five-leaf aralia (Acanthopanax sieboldianus)
- summersweet clethra (Clethra alnifolia)
- smooth hydrangea (Hydrangea arborescens)
- black jetbead (Rhodotypos scandens)
- snowberry (Symphoricarpos spp.)
Only a limited number of evergreens do well in shady areas. Yews (Taxus spp.) are evergreen shrubs that do well in sun or shade. However, they do require well-drained soils. Yews often die in wet, poorly drained soils. They are also prone to winter injury when planted in windy, exposed sites. Yews tolerate pruning well and are often pruned into formal hedges.
The Canadian hemlock (Tsuga canadensis) is an attractive, graceful tree. Hemlocks perform best in cool sites with well-drained, moist soils. Avoid windy, exposed sites and hot, dry locations. Hemlocks may eventually attain a height of 40 to 50 feet when grown in favorable sites. In Iowa, Canadian hemlocks grow best in the eastern portion of the state.
Rhododendrons (Rhododendrons spp.) are broadleaf evergreens that do well in partial shade. However, only a small number of rhododenrons can be successfully grown in Iowa. 'PJM' (lavender-pink flowers), 'Aglo' (light pink flowers with dark pink throats), and 'Olga Mezitt' (pink flowers) are three hardy cultivars which can tolerate our harsh winter weather. When planting rhododendrons, site selection is extremely important. Rhododendrons perform best in protected sites in partial shade. An area that receives morning sun and afternoon shade would be a good site for rhododendrons. Windy and exposed sites should be avoided. Rhododendrons also require well-drained, acid soils. An excellent way for home gardeners to lower their soil pH is to incorporate Canadian sphagnum peat into the soil prior to planting.
Selecting and planting shade tolerant trees and shrubs, along with suitable annuals and perennials, can transform bare shady areas into attractive landscape sites.
This article originally appeared in the April 3, 1998 issue, pp. 32-33.