Scientific: Leucaena leucocephala (Synonyms: Leucaena glauca, Leucaena latisiluqua, Mimosa leucocephala)
Common: lead tree, white lead tree (there are MANY other common names for this tree in many languages of indigenuous peoples within tropical areas around the world)
Family: Fabaceae (Leguminosae)
Origin: From Mexico south into tropical Latin America, but has naturalized in tropical and subtropical regions worldwide (pan-tropical).
Pronounciation: Lew-ka-EN-a lew-co-SEPH-a-la
INVASIVE ALERT: Lead tree is a fecund naturalizer in tropical, subtropical, and arid climates (where there's water) worldwide. In recent decades, it has established a 'naturalized' foothold in the south and central sections of the city of Phoenix and is now rapidly spreading like "The Blob" throughout the metropolitan area. Shown in this image are lead trees that germinated from seed in place of where once grew Pyrus calleryana trees on the Arizona State Tempe campus. And yes, I know what you're thinking. Callery pear IS a lousy tree choice for the Phoenix area....and you're right.
To summarize, lead tree is clearly vigorously invading the Phoenix urban ecosystem and as such should be thought of as an invasive species. Because of its aggressive invasiveness, I would STRONGLY DISCOURAGE anyone from planting this tree in any Arizona landscape.
Hardiness zones
Sunset 13-24
USDA 9-11
Landscape Use: Medium-sized, mesic or oasis tree for light shade and spring floral accent. Able to grow rather well in highly neglected sites. In irrigated Phoenix landscapes (the oasis desert), this tree is highly invasive!!!
Form & Character: Open-canopied upright tree with an eventual broad based canopy, tropical effect, agressive, fecund (like rabbits), unruly.
Growth Habit: Semi-deciduous, woody, perennial broadleaf weed (cough...cough...tree), very fast upright growth from 15 to 50 feet, weak wooded and brittle, clumping, sometimes forming little urban thickets.
Foliage/Texture: Alternate, twice pinnately compound leaves, to 10-inches long; secondary rachis about 5 (4 to 9) pairs, up to 3- to 4-inches long, leaflets about 12 (11 to 17) pairs, leaflets linear and less than 1/8-inch long, trunk is brownish to gray, smooth, young branches and stems have prominent lenticels; medium texture.
Flowers & Fruits: Pin cushion like pom-pom flower heads in terminal racemes, greenish yellow or white, produced during spring. Fruits are extended brownish pods (green when immature) to 6-inches long, clustered, persistent on the tree, unattractive.
Seasonal Color: Minimal seasonal color, though flowers during late April to early May are a subtle accent.
Temperature: Sadly, lead tree is very tolerant of Phoenix temperatures.
Light: Full sun to partial shade.
Soil: Sadly, lead tree is highly tolerant of Phoenix soils.
Watering: Lead tree is incredibly adaptable to a diversity of soil moisture regimes. Irrigation in Phoenix strongly stimulates growth.
Pruning: Elevate canopy base, but better yet agressively rouge emergent seedlings when they are small!!
Propagation: Prolific seed producer, propagates (itself) very easily by seed.
Disease and Pests: Sadly none, though this tree itself has become an invasive pest in Phoenix.
Additional comments: Lead tree as a nitrogen fixer (symbiont Rhizobium bacteria) is one of the highest quality and most palatable fodder trees of the tropics for ruminant animals. And no, there are no cows grazing in the backyards of Phoenix homes, though the stench of local dairies in the southeast and southwest portions of the Phoenix metro tend to irritate some. Otherwise, it's rumored that humans will experience hair loss, reduced thyroid function, goiter, and infertility if "we" consume lead tree foliage and seeds because it contains the toxic amino acid, mimosine, which we're unable to metabolize in our digestive tracts because we lack the proper intestinal bacteria that are otherwise present in cows. Last I checked though around Phoenix, I've not seen any "humans" out-and-about grazing on lead trees.
