High-altitude gardening can be challenging, and finding the trees for the landscape that will survive in high altitudes might be a daunting task. Even native trees struggle to survive. The growing season at high altitudes tends to be very short -- typically June through September. Temperatures tend to get cool at night and there may be unexpected frosts even if the daytime temperatures are high. Soils tend to be rocky and coarse, and there are occasional strong winds. Furthermore, high-altitude climates can range from cold alpine to high desert environments.
Deciduous trees are trees that lose their leaves in winter. High-altitude trees should have leaves that emerge late in the season to avoid frosts. Poplar, Aspen (both are Populus spp.) and birch (Betula spp.) grow quickly are found in high altitudes from Canada to Mexico. Oaks (Quercus spp.) and a few tough maples (Acer spp.) are also common. Most are hardy within U.S. Department of Agriculture zones 3 to 8. In high-altitude desert areas, trees have to adapt to both cold and high heat, and trees like Acacia and mesquite (Prosopis spp., USDA zones 8 to 10) are common.
Flowering trees in high altitudes may be smaller than they would be if grown in less harsh conditions. Many of the flowering crabapples (Malus spp.) tolerate harsh conditions, particularly later-flowering varieties. Hawthorns bloom later in the season and tolerate high altitude conditions, with flowers nearly covering the branches in late spring. Purple sand cherry (Prunus x cistena) grows more like a shrub in high altitude conditions, but is tough and bears a profusion of single delicate pink flowers. Most grow well in USDA zones 3 to 8. In high-altitude deserts, the desert willow (Chilopsis spp., USDA zones 6 to 9) is a stunning weeping tree with frilly pink flowers.
It's possible to have fruiting trees at high altitudes, but the fruits may be smaller or less plentiful. Many apples (Malus spp.) and pears (Pyrus spp.) will tolerate these conditions, particularly those that mature early. "State Fair," "Yellow Transparent" and "Earligold" are a few early-bearing apples, and "Clapp's Favorite," Honeysweet," "Moonglow" and "Summercrisp" are a few early-bearing pear choices . Apricots and cherries (both Prunus spp.) all bear in July to August and nearly all plums (Prunus spp.) bear fruit in August, making them suitable to high-altitude areas. Any of these trees might do well in a high desert climate if the trees get enough chill hours (hours in the cold to induce fruit production). Most of these trees grow well in USDA zones 3 to 8.
When driving a mountain highway it's easy to tell when you're at a high elevation. Most vegetation gives way to pine (Pinus spp.) and juniper (Juniperus spp.) trees. Ponderosa (P. ponderosa), jeffrey (P. jeffreyi) and pinyon (P. edulis) pines are common from Canada to Mexico, and in the extreme high elevations you can find the twisted bristlecone pine (P. aristata). The USDA zones for pines range from 2 to 9. High desert regions may have junipers, like the California (J. californica) or western juniper (J. occidentalis, both in USDA zone range of 4 to 9). Cypress also tolerate high desert conditions, particularly the Arizona cypress (Cupressus arizonica) and tecate cypress (C. forbesii, both USDA zones 8 to 10).
- Denver Plants: High Altitude Deciduous Trees
- Theodore Payne Foundation: High Desert Plants
- Desert USA: The Mesquite
- Pima County Cooperative Extension: Chilopsis linearis
- University of Idaho: Growing Fruit Trees in Short-Season Gardens
- Mojave Desert: California Juniper
- Glendale Public Library: Cupressus arizonica v. glabra-Blue Arizona Cypress
- Utah State University: Pinyon Pine
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