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 clo ...

(''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 the cooler regions of the northern hemisphere, where they are found in lowland forests in the high la ...

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

hardwoods Hardwood is wood from angiosperm 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 ...

. In the

Sonoran Desert The Sonoran Desert () is a hot desert and ecoregion in North America 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 and California). It ...

, Palo Verde,

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

and

mesquite Mesquite is a common name for some plants in the genera ''Neltuma'' and '' Strombocarpa'', which contain over 50 species of spiny, deep-rooted leguminous shrubs and small trees. They are native to dry areas in the Americas. Until 2022, these ge ...

trees serve as nurse trees for young saguaro cacti. 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.

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