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March 1, 2009

Restoring Shady Landscapes

Master Gardener Column 2/28/09

Within our nearby forests, canyons, and drainages there are many places where shade loving native plant communities thrive. Most often these plant communities are found in areas that receive more moisture from runoff and have deeper, well drained soils. Some, however, are adapted to drier, poorer soils. In and around Flagstaff much of the shady, under-story growth has been lost either to development or past forestry practices. We can use the template or example of existing plant communities to restore the under-story of the interface between the forest and the shady, moister microclimates created by the urban environment. In the appropriate location these communities will thrive without supplemental irrigation.

The under story can be viewed as having two layers: an upper layer of small trees and shrubs and a lower layer of perennials and grasses. The lack of upper layer under-story plants results in a lack of screening and privacy for humans in residential landscapes as well as a lack of cover and habitat for birds. Small trees and shrubs that dominate this upper layer throughout the Flagstaff area include: Gambel oak, alligator bark juniper, Rocky Mountain juniper, wax currant, three leaf sumac, Woods' rose, and New Mexican locust. All of these can be planted directly under ponderosa pine that lack lower limbs to provide screening. Other upper layer trees and shrubs with more specific site requirements are sited in the examples below.

Provided below are three examples of lower layer native plant communities and their recommended placement within urban/suburban Flagstaff. The recommendations are based on soil type and availability of water. These are not complete lists but include common community representatives available at nurseries. The examples are derived from three places: Shultz Pass, Pumphouse Wash, and the forested rim of Sinclair Wash near Willow Bend. All three of these examples share the common upper layer trees and shrubs mentioned above.

The plant community of Shultz Pass will tolerate heavier soils amended with organic matter and thrive on increased moisture harvested from run-off such as a downspout leading to a depression. Additional shrubs include snowberry and buckbrush. Arizona fescue is the most common grass. Perennials include white cranesbill, golden pea, meadow-rue, false solomon seal, Arizona honeysuckle, mountain parsley, Arizona valerian, red columbine, princely daisy, aspen sunflower, and golden columbine. This community will work well in areas like Boulder Point and University Heights where ponderosa are still providing most of the shade and sloping lots provide opportunities for water harvesting.

The Sinclair Wash rim community is well adapted to drier sites or rocky slopes under ponderosa pine without the potential for water harvesting. Shrubs include buckbrush, creeping mahonia, and golden currant. Arizona fescue and blue grama are common grasses here. One perennial community could include mat penstemon, milk-vetch, leather flower, pussy-toes, meadow-rue, and scarlet bugler. Goldenrod often provides a monoculture groundcover beneath a ponderosa. On rocky slopes bulb panicum is a small ornamental bunch grass. Perennials include meadow-rue, Arizona valerian, Arizona honeysuckle, red columbine, scarlet bugler, and pussy-toes.

Pumphouse Wash provides a template for shady canyon plantings that will receive limited mid-day sunlight. This is an ideal community for the urban environment. Areas between buildings that have sandy soils rich in organic matter provide the canyon microclimate enjoyed by this community. Where space permits the colorful bigtooth maple and thinleaf alder are small tree additions to the upper layer of the under-story. Shrub additions include New Mexican raspberry (a large upright shrub), California buckthorn, snowberry and redtwig dogwood. Grass-like western sedge provides an excellent groundcover in addition to the perennials listed for Shultz Pass. Canadian violet, Arizona honeysuckle, and mountain lover can provide ground cover for even deeper shade.

Landscaping suggestions for shady areas:
• Grade to direct runoff to shade areas.
• Include recommended small trees to under-story.
• Add organic compost to soil when planting.
• Maintain 3 inches of surface mulch until the community is well established.
• Remove most, but not all, pine needle fall.
• Plant July through September to conserve water
• Water only to establish plants.
• In ground irrigation not required.
• Fertilizer not required.

Nigel Sparks is a landscaper and horticulturalist associated with Flagstaff Native Plant and Seed. Dana Prom Smith, coordinating editor of the Master Gardener Column for Coconino County Cooperative Extension, can be contacted at stpauls@npgcable.com. For more information about the Master Gardener Program, call Hattie Braun, Coordinator of the Master Gardener Program, at 774-1868 ext.17 or visit our Web Site: highelevationgardening.arizona.edu.

Posted by maxmaddy at March 1, 2009 5:04 PM