Mesquite is a common name for some 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 ground. As a legume, mesquites are one of the few sources of fixed nitrogen in the desert habitat.
They are deciduous and depending on location and rainfall have either deep or shallow roots. Prosopis is considered long-lived because of the low mortality rate after the dicotyledonous stage and juveniles are also able to survive in conditions with low light and drought. The Cahuilla indigenous people of western North America were known to eat the seeds of mesquite.
Mesquite trees can range from small, shrub-like sizes to trees that are about 20 to 30 feet (6 to 9 meters) tall. In ideal conditions or with certain species, they might grow even taller, potentially up to 50 feet (15 meters). They often have a spread that’s as wide as they are tall, if not wider, giving them a somewhat sprawling appearance with branches close to the ground in open settings.
The leaves are usually compound, pinnate or bipinnate, meaning they are divided into smaller leaflets. This structure gives them a fern-like or feathery appearance. Each leaf consists of numerous small leaflets. The number and size of these leaflets can vary by species, but generally, there are many small, narrow leaflets along each leaf stalk.
The flowers are small and yellowish or creamy white. They can also appear greenish-yellow, depending on the species. Flowers grow in elongated, cylindrical spikes or catkins. These spikes can range from 2 to 4 inches in length, packed densely with tiny flowers. Each individual flower is quite small, often less than a centimeter, and has a simple structure with stamens that are noticeably longer than the petals, giving the spike a somewhat fuzzy or brush-like appearance.
Mesquite trees generally bloom in the spring, but the exact timing can vary with species and local climate conditions. Some might have a secondary bloom in response to rain in late summer or early fall. The flowering period can last several weeks, providing a prolonged opportunity for pollination. The flowers are perfect, meaning they have both male (stamens) and female (pistil) parts. However, cross-pollination is common due to the timing of maturity of these sex parts or through mechanisms that favor outcrossing.
Mesquite bark is dark brown to grayish-brown. As the tree ages, the bark can become darker and sometimes almost blackish. Young trees or branches have smoother bark, but as mesquite trees mature, the bark becomes rough, deeply furrowed, and can appear quite rugged with thick, scaly ridges or plates. This texture provides a distinctive look that can be quite striking.
Facts About Mesquite Trees
Mesquite trees are generally considered to have a moderate to fast growth rate. Under optimal conditions, they might grow 2 to 3 feet per year, but this can vary widely with water availability, soil quality, and species. In arid conditions, their growth can be much slower due to the need to develop deep root systems first. Young mesquite trees might focus more on root development than above-ground growth, which is why they might seem slow-growing at first but can accelerate once established.
Mesquite trees can live for a very long time. Some species are known to live for 200 years or more. The longevity of mesquite trees is attributed to their resilience against drought, their deep taproot system, which not only finds water but also anchors them securely against winds, and their ability to regenerate from the root crown after damage or cutting.
Mesquite trees are generally deciduous in response to cold or extreme drought, dropping their leaves to conserve water or protect against cold temperatures. However, in mild winters or with sufficient moisture, they might retain leaves longer or even year-round in some climates.
Mesquite flowers are primarily pollinated by insects, particularly bees. They produce a fragrance that attracts these pollinators. The abundance of nectar also makes mesquite trees significant for honey production.
In traditional medicine, parts of the mesquite, including the bark, have been used for various remedies. The bark has been employed in treatments for stomach issues, skin conditions, and as an astringent due to its tannin content.
Some species of mesquite, when introduced to new environments, can become invasive, outcompeting native plants due to their drought resistance and ability to spread rapidly via seeds. In areas where different mesquite species coexist, they can hybridize, leading to trees with mixed characteristics.
Factors Influencing Growth and Lifespan
- Water Availability: Although adapted to dry conditions, more available water can lead to faster growth but might not extend lifespan.
- Soil: They prefer well-drained soils but can tolerate a variety of soil types, including alkaline and saline conditions, which many other trees cannot endure.
- Climate: They thrive in hot climates but can be susceptible to prolonged freezes, which might affect their lifespan or growth rate.
- Human Intervention: Pruning, cutting for wood, or clearing for land development can significantly impact individual tree lifespan.
Adaptations for Arid Environments
- Reduced Water Loss: The small size of the leaflets and their compound arrangement reduce the leaf surface area exposed to the sun, thereby minimizing transpiration and conserving water.
- Pubescence: Some mesquite species, like the Velvet Mesquite, have fine hairs on their leaves (trichomes), which can help in trapping moisture, reducing wind speed across the leaf surface, and reflecting excess light.
- Stomatal Control: Mesquite trees can control the opening and closing of their stomata (the pores on the leaves through which gases and water vapor exchange occurs) very efficiently to minimize water loss during the hottest parts of the day.
Types of Mesquite Tree
Honey Mesquite (Prosopis glandulosa)
- Distribution: Native to the southwestern United States and northern Mexico.
- Characteristics: It has a somewhat rounded canopy, with bipinnate leaves. The tree can grow up to 30 feet tall but often remains shrubby in harsh conditions. Its flowers are creamy-yellow spikes, and it produces long, straight pods.
Velvet Mesquite (Prosopis velutina)
- Distribution: Found in Arizona, parts of California, and Sonora, Mexico.
- Characteristics: Known for its velvety, hairy leaves and pods when young. It can grow quite large for a mesquite, up to 30-40 feet in height. The bark is dark and becomes deeply furrowed with age. Its pods are somewhat curved.
Screwbean Mesquite (Prosopis pubescens)
- Distribution: Native to the southwestern United States, particularly in desert areas like the Sonoran Desert.
- Characteristics: Named for its distinctive, tightly coiled or spiraled pods, which resemble screw threads. It has smaller, more delicate leaves compared to other mesquites. Typically grows in floodplains and near water sources.
Argentine Mesquite (Prosopis alba)
- Distribution: Originally from South America, particularly Argentina, but introduced in other regions for its utility.
- Characteristics: It has a high canopy and can grow quite tall. The pods are somewhat flat and long, with a sweet taste, making them very popular for both human consumption and livestock feed.
Chilean Mesquite (Prosopis chilensis)
- Distribution: Native to South America, specifically in Chile, Argentina, and Peru.
- Characteristics: Similar to other mesquites but adapted to slightly different environmental conditions. It’s used for shade, timber, and the pods are used for food.
Black Mesquite (Prosopis nigra)
- Distribution: Found in Argentina, Bolivia, and Paraguay.
- Characteristics: It’s known for its dark bark and wood. The tree can be identified by its dark, almost black, deeply fissured bark, and it produces sweet pods used for various purposes.
Prosopis pallida (Kiawe in Hawaii, where it’s known)
- Distribution: Native to Colombia, Ecuador, and Peru, but famously invasive in places like Hawaii.
- Characteristics: Often has a very spreading form, providing ample shade. Its pods are quite nutritious and have been used historically for fodder and human food.