Short summers yield a concentrated blooming season with perennial flower combinations not typically found at lower altitudes where flowering times don't always overlap. In the mountains especially, high precipitation levels increase the variety of perennials that can be grown without alot of additional irrigation. As well, the concentration of sunlight at high altitudes intensifies flower pigments, creating stunning color displays in the garden.
The First Step in Creating a High-Altitude Garden
Successful gardeners should first look to the landscape around them, emulating the natural environment and native plants found on and near their site. A visit to a local nursery will also generate detailed knowledge about plant materials that thrive in a particular region. It is important to note here that high-altitude gardening is also defined by latitude; growing conditions at 7,000' in northern Arizona are very different than the conditions at the same altitude in Wyoming. Finding out the length of the growing season, average frost dates, and average first and last snowfalls will give a general indication on the length of the growing season. Consulting a USDA hardiness zone map is always recommended.
Lack of good soil can pose the biggest limitation to high-altitude gardening. A gardener's best bet is to either import good soil, or amend the existing soil with appropriate additives such as sphagnum peat or wood chips for increased permeability, water infiltration and retention, drainage, aeration and structure.
Mulch is an absolute necessity in high altitude gardening. It reduces evaporation and runoff, inhibits weed growth, and creates an attractive appearance. Mulches also moderate soil temperatures, helping to warm soils in the spring and cool them in the summer. Consider organic mulches such as shredded bark, ground cork, ground corncobs, or walnut shells.
MicroclimatesCreating microclimates within the garden will encourage a wider variety of plant material. Areas of more extreme moisture content, shade, warmth, and protection exist naturally on a site, however, they can also be created simply by including rock and stone in a landscape. Stone absorbs heat, moderates the soil temperatures, and creates moist pockets of shade. Wind is often a constant presence in mountainous, high altitude environments. Often, winds can cool a site below thermometer readings and dehydrate vegetation. A microclimate that is very sunny but wind sheltered has many more plant possibilities. Plants in open, exposed areas need to be able to tolerate the intense sun of higher elevations.
Plants that can survive in exposed areas include:
- Trees: Blue Spruce, Ponderosa Pine, Bosnian Pine, Austrian Pine, Scotch Pine, Limber Pine, Swiss Stone Pine, Mugo Pine, Rocky Mountain Juniper, Bristlecone Pine, Gambel Oak, Bur Oak.
- Shrubs: Mountain Mahogany, Cliffrose, Peashrubs, Sumac, Rock Spirea, Four Wing Saltbush, Artemesias, Potentillas, Barberry, Buffalo Berry, and shrub junipers.
- Perennials: Penstemons, Mexican Hat, Boltonia, Blue Flax, Asters, Gaillardia, Yarrow, Nepeta, Thyme, Sulfur Buckwheat.
- Grasses: Grama, Sheep Fescue.
A microclimate that is sunny, but sheltered from the wind allows for many more plant possibilities. Plant suggestions for this area include:
- Trees: White Fir, White Pine, Limber Pine, American Smoketree, Green Ash, Honey Locust, Mountain Ash, non-fruit producing Crabapple and Plum, Linden, Hawthorn, Amur Maple.
- Shrubs: Apache Plume, Butterfly Bush, Gooseberry, Honeysuckles, Serviceberry, Blue Mist Spirea, Lilacs, Forsythia, Cistena Plum, Western Sandcherry, Brooms, Roses.
- Perennials: English Lavender, Purple Coneflower, Jupiter's Beard, Evening Primrose, Virginia Creeper, Trumpet Vine, Coreopsis, May Night Salvia, Solidago, Russian Sage, Oriental Poppy, Delphinium, Shasta Daisy.
- Grasses: Blue Fescue, Blue Oat Grass, Feather Reed Grass, Ribbon Grass, Switchgrass, Tufted Hair Grass.
The north side of a high wall or building is a microclimate that is moister than the sunny areas. Be alert to selecting species that can tolerate frozen ground for weeks at a time.
Suggestions include:
- Trees: White Fir, Gambel Oak, Peachleaf Willow, Aspen, Amur Maple.
- Shrubs: Dogwood, Spirea, Willow, Colorado Barberry, Oregon Holly Grape, Serviceberry.
- Perennials: Columbine, Lungwort, False Nettle, Ornamental Comfry, Daffodils, and other shade-loving bulbs.
Yet another microclimate that protects plants from harsh winds and blazing sun is the area found under a tree canopy. Here, soils maintain a higher degree of organic matter and a thick mulch of leaves or other porous material.
Suggestions include:
- Shrubs: Currant, Chokecherry, Silverberry, Serviceberry, Viburnum, Mahonia, Mountain Lover, Kinnickinnick, Wood's Rose.
- Perennials: Vinca, Saponaria, Veronica, Columbine, Whipple's Penstemon.
Successful Perennials
Cold temperatures and short growing seasons are the main variables that mountain plants must contend with. Frosts in late spring and early summer make growing perennials whose flowers are frost sensitive (e.g. Peonies) difficult. However, there are still many perennial plant choices for high-altitude gardens available from which to choose. Planting season for high-altitude gardeners really begins as soon as the snow melts and the soils thaw and warm. Listed below are proven successful perennial groups with recommended species and cultivars:
Border Perennials suggestions include:
Yarrow, Campanula, Delphinium, Lupine, Catmint, Poppy, Penstemon, Salvia, Veronica, Black-eyed Susan, Blanket Flower, Cranesbill, Heliopsis, Ladies' Mantle, Lamb's ears,Lychnis or Maltese Cross, Mondarda, Painted Daisy, Purple Coneflower, Scabiosa, Shasta Daisy
Groundcover suggestions include:
Hardy Ice Plant, Garden Pinks, Candytuft, Creeping Phlox, Soapwort, Creeping Speedwell, Creeping Thyme
The above information can be verified and expanded upon with a visit to High Coutry Gardens, a Santa Fe, New Mexico-based nursery.
Wildlife
Gardening at high altitudes also means sharing the environment with its native inhabitants. Deer, elk, and bear can ruin a garden in seconds. Many communities have implemented stringent planting regulations to inhibit wildlife visitation. For example, bears feed heavily on fruits and berries in the fall. Native shrubs such as chokecherry, currant, raspberry, and serviceberry are staples. As a result, many communities now require that any new flowering trees be non-fruit producing, and that native berry-producing shrubs be eliminated from the landscape plans. Elk can decimate a tree with their antlers in no time. Gardeners living in elk habitat should consider fencing evergreens and branching deciduous trees from October until April.
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