Nuts That Grow at High Altitudes

How High

• At extremely high altitudes, you won't find trees of any kind, but at elevations where people live and garden, some nut trees will survive. Definitions of high altitude vary. For example, the University of Idaho Extension defines 4,500 feet as high elevation for gardeners, while Wyoming Extension uses 6,000 feet. Generally, only nut trees that are reliably hardy to at least U.S. Department of Agriculture zone 4, where winter temperatures dip to -30 F, will survive such altitudes. In several western states, the pinyon pine (Pinus edulis), which produces pine nuts, naturally grows at elevations between 4,500 and 7,500 feet, according to Utah State University Extension. Cultivated nut trees that can grow at these altitudes include those from the Carya genus: hickories and pecans; the Corylus genus: filberts or hazelnuts; and the Juglans genus: butternuts and walnuts.

Chilling Requirements

• Tree hardiness is not the only issue for producing nuts at high altitudes. Although many nut trees will survive the harsh conditions, other issues may thwart a harvest. Pinyon trees are adapted to the climactic conditions in their natural range, but growing most nut trees at higher elevations requires attention to chilling hours. Longer chilling requirements mean delayed flowering and spring growth. Thus, nut trees with greater chilling hour requirements are better choices for high altitude gardens with short growing seasons. Some filberts, pecans and walnuts have chilling requirements above 1500 hours, so are well-suited for colder climates, notes Arizona Cooperative Extension.

Pollination Issues

• Self-pollinating tree varieties are also more likely to bear nuts because insects and wind have less distance to travel to accomplish their work. Most nuts, including pine nuts, require cross-pollination from other cultivars. "Hansen" and "Colby" walnuts and "Winkler" hazelnuts are reportedly self-fertile, notes Purdue University Cooperative Extension Service horticulturalists.

Considerations

• Many other variables affect nut production at high altitudes. Once pollinated, temperature and rainfall must remain favorable for the nuts to mature. Late frosts or other harsh weather conditions may reduce or eliminate nut yields. Those who garden at higher elevations may value nut trees for the role they serve in the landscape, as well as the harvest.