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High elevation landscapes: unique opportunities

While it may not be the model that most landscapers choose, the habitats found on high plateaus, summits and ridgetops present unique communities of native species and some interesting options.

Seventeen different ecosystems described as ridgetops and summits are reported in the Poconos. While they vary slightly in composition and observed species, they share some common and potentially useful themes for landscapers who prefer to work with a challenging habitat, rather than attempting to amend it.

Scant, if any, tree canopy is a hallmark of many high elevation sites, which in turn creates opportunities for a variety of unique shrubs and many grasses. Above and top: National Park Service photos

A common theme among high elevation sites are conditions that appear to run counter to almost all materials for home landscapes. Soils are generally shallow, dry to the point of xeric, excessively drained, acidic and sands - very often coarse sands and rock.

Local climate can be harsh. Weather forecasts that call for wintery conditions "in higher elevations" generally refer to those about 1,200 feet and most certainly the Allegheny plateau in the northwestern area of the region. Shallow soils and rough weather cause a considerable hazard to trees, which often means the region is sparse in canopy and limited to Pinus rigida, one of the few conifers to actually relish forest fires. If trees common to the region are present, they are likely to be stunted to almost tall-shrub stature.

Working with shrubs

Thus Quercus ilicifolia (bear oak) and Quercus prinoides (dwarf chinkapin oak), which grow to a height of 12 to 15 feet, frame plant selections for this habitat: sandy, rocky, well-drained, nutrient-poor. Prospects, however, are not necessarily bleak.

These are excellent soils for a substantial number of flowering and fruiting shrubs to use for the major elements of design. All are durable, but Kalmias, Epigaea repens and Comptonia peregrina can be all but impossible to transplant; nursery stock is best.

Taller shrubs

Amelanchier arborea (shadbush) - About 20 feet

Kalmia latifolia (mountain laurel) - 15 feet

Rhododendron periclymenoides (Pinxter-flower) - 10 feet

Aronia melanocarpa (black chokeberry) - 10 feet

Vaccinium stamineum (deerberry) - 6 feet

Viburnum acerifolium (maple-leaf viburnum) -6 feet

Comptonia peregrina (sweet fern) - 5 feet (and deer proof)

Shorter shrubs

Gaylussacia baccata (black huckleberry) - 3 feet

Kalmia angustifolia (sheep laurel) - 3 feet

Vaccinium pallidum (lowbush blueberry) - 3 feet

Vaccinum angustifolium (low sweet blueberry) - 30 inches

Low shrubs and subshrubs

Arctostaphylos uva-ursa (bearberry) - less than 12 inches

Gaultheria procumbens (winterberry) - less than 12 inches

Epigaea repens (trailing arbutus) - less than 6 inches

In richer environments (such as on broad ridges where soils become a bit richer and habitat is more mesic), Lindera benzoin (spicebush) and Hamamelis virginiana (witch hazel) are often found under a more substantial tree canopy that usually features Quercus rubra (Northern red oak) and Quercus prinus (Chestnut oak) along with the inevitable Acer rubrum (red maple).

Grasses and ferns for dramatic effect

Comptonia peregrina, or sweet-fern, is actually a shrub and can form dense stands up to six feet tall

Shortage of tree cover is welcomed by many sturdy gramanoids that thrive in sterile, sandy, dry soils and can be used as masses or specimen plants to create some dramatic effect. As always, grasses and sedges are absolutely deer proof.

Common in the dry high elevations are:

Andropogen gerardii (big bluestem) - 3 to 10 feet

Panicum virgatum (switchgrass) - to 6 feet

Sorghastrum nutans (Indian grass) - 3 to 6 feet

Bromus pubescens (Canada brome) - 24-60 inches

Schizachyrium scoparium (little bluestem) - 20-45 inches

Deschampsia flexuosa (wavy hairgrass) - 12-40 inches

Eragrostis spectabilis (Purple lovegrass) - 12-24 inches

Danthonia spicata (poverty grass) - 8-24 inches

Carex pensylvanica (Pennsylvania sedge) - 4-16 inches

Carex lucorum (Blue Ridge sedge) - less than 6 inches, but may be difficult to find

These represent something of a catalog of classic prairie grasses that extended across most of temperate North America - particularly the Great Plains, and are widely respected for their ability to prevent erosion because roots are dense and generally run very deep. Depth of roots is what allows the grasses to withstand prolonged periods of drought. Carex pensylvanica, which thrives in dry, sterile shade, is the best alternative to attempting lawns in wooded areas and spreads methodically to carpet large areas.

A stand of Dennstaedia punctilobula (hay scented fern) will never be bothered by deer and will rapidly fill open areas. Keep it in check with a lawnmower.

Two species of ferns can be used for sweeping backgrounds or dramatic pools of green.

Deschamsia flexuosa (wavy hairgrass) is a thin, delicate-looking but very sturdy perennial that works as accents or as pure stands in masses

 

About Pennystone

The Pennystone project provides information relating to sustainable landscape practices using native species, with emphasis on the northeastern counties of Pennsylvania.

Common in these habitats are Pteridium aquilinum (northern bracken fern, 18-50 inches), which is every common in these habitats and Dennstaedtia punctilobula (hayscented fern, 15-30 inches).

Both are ignored by deer, but need room to run. They spread aggressively through long-reaching rhizomes, a trait that can be used to advantage for building large, care-free and dramatic sweeps of foliage with virtually no maintenance. Both will grow taller in part sun than in full shade.

Other herbaceous perennials that may be called into service for these types of habitats are Corydalis sempervirens (rock harlequin), Maianthemum canadense (Canada mayflower), Aralia nudicalis (wild sarsaprarilla), Polygonatum biflorum (Solomon's seal), Waldsteinia fragaroides (barren strawberry), Eurybia divaricata (white wood aster) and Symphyotrichum cordifolium (blue wood aster), all of which serve well in dry sandy soil.

Carex pennsylvanica (Pennsylvania sedge) is one of the must-have species for almost all types of woodland landscapes, especially those that are dry, sterile and in heavy shade

Conclusions

While at first glance high elevation sites may present a gloomy prognosis for creative landscaping, the use of sturdy perennials in especially large masses can create a variety form and complexity that adds up to drama - but with very little water and soil supplements. It may not be as extensive as options for a lush wetland, but xeric landscapes can exude considerable beauty in their simplicity.

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