A nurse tree is a larger, faster-growing tree that shelters a smaller, slower-growing tree or plant. The nurse tree can provide shade, shelter from wind, or protection from animals who would feed on the smaller plant.

For example, the Norway Spruce

Norway Spruce

Norway Spruce is a species of spruce native to Europe. It is also commonly referred to as the European Spruce.- Description :...

 (Picea abies) and Larch

Larch

Larches are conifers in the genus Larix, in the family Pinaceae. Growing from 15 to 50m tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains further south...

 (Larix) can function as a nurse for hardwoods. In the Sonoran desert

Sonoran Desert

The Sonoran Desert is a North American desert which straddles part of the United States-Mexico border and covers large parts of the U.S. states of Arizona and California and the northwest Mexican states of Sonora, Baja California, and Baja California Sur. It is one of the largest and hottest...

, Palo Verde

Parkinsonia

Parkinsonia , also Cercidium , is a genus of flowering plants in the pea family, Fabaceae. It contains about 12 species that are native to semi-desert regions of Africa and the Americas...

, Ironwood

Olneya tesota

Olneya tesota is a perennial flowering tree of the Fabaceae family, legumes , which is commonly known as Ironwood or Desert Ironwood. It is the only species in the monotypic genus Olneya...

 or mesquite

Mesquite

Mesquite is a leguminous plant of the Prosopis genus found in northern Mexico through the Sonoran Desert and Chihuahuan Deserts, and up into the Southwestern United States as far north as southern Kansas, west to the Colorado Desert in California,and east to the eastern fifth of Texas, where...

 trees serve as nurse trees for young saguaro cacti

Saguaro

The saguaro is a large, tree-sized cactus species in the monotypic genus Carnegiea. It is native to the Sonoran Desert in the U.S. state of Arizona, the Mexican state of Sonora, a small part of Baja California in the San Felipe Desert and an extremely small area of California, U.S...

. As the Saguaro grows and becomes more acclimated to the desert sun, the older tree may die, leaving the saguaro alone. In fact, as the Saguaro grows larger it may compete for resources with its nurse tree, hastening its death. Consequently, young saguaros are often seen near trees, but old saguaros are not.