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, and protection from animals that would feed on the smaller plant and significant changes in temperature. Fallen leaves from the nurse tree fertilize the ground underneath creating nutrient-rich soil for the saplings and vegetation beneath. Some nurse trees act as Nitrogen-fixing agents in the soil. The nurse tree relationship occurs both naturally and via human intervention.

Examples

The

Norway spruce ''Picea abies'', the Norway spruce or European spruce, is a species of spruce native to Northern, Central and Eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, 9–17 cm long. It is very close ...

(''Picea abies'') and

larch Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains furt ...

(''Larix'') can function as nurses for

hardwoods Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

. In the

Sonoran Desert The Sonoran Desert ( es, Desierto de Sonora) is a desert in North America and ecoregion that covers the northwestern Mexican states of Sonora, Baja California, and Baja California Sur, as well as part of the southwestern United States (in Arizona ...

, Palo Verde,

ironwood Ironwood is a common name for many woods or plants that have a reputation for hardness, or specifically a wood density that is heavier than water (approximately 1000 kg/m3, or 62 pounds per cubic foot), although usage of the name ironwood in E ...

and

mesquite Mesquite is a common name for several plants in the genus ''Prosopis'', which contains over 40 species of small leguminous trees. They are native to dry areas in the Americas. They have extremely long roots to seek water from very far under grou ...

trees serve as nurse trees for young

saguaro cacti The saguaro (, ) (''Carnegiea gigantea'') is a tree-like cactus species in the monotypic genus ''Carnegiea'' that can grow to be over tall. It is native to the Sonoran Desert in Arizona, the Mexican state of Sonora, and the Whipple Mountains ...

. As the Saguaro grows and becomes more acclimated to the desert sun, the older tree may die, leaving the saguaro alone. As the Saguaro grows larger, it may compete with its nurse tree for resources, hastening its death. Consequently, young saguaros are often seen adjacent to trees, while old saguaros are not.National Park Service. How Saguaros Grow.
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References

*John Vandermeer. Saguaros and Nurse Trees: A New Hypothesis to Account for Population Fluctuations. The Southwestern Naturalist, Vol. 25, No. 3 (Nov. 14, 1980), pp. 357–360. Trees Forest ecology {{tree-stub