Albizia julibrissin 'Alba': 'Alba' Mimosa Tree1
This fast-growing, deciduous tree has a low branching, open, spreading habit and delicate, lacy, almost fern-like foliage. Fragrant, silky, white puffy pompom blooms, two inches in diameter, appear in abundance from late April to early July creating a spectacular sight. The tree produces numerous seed pods and harbors insect (webworm) and disease (vascular wilt) problems. Although rather short-lived (10 to 20 years), mimosa is popular for use as a terrace or patio tree for its light, dappled shade and tropical effect. Its deciduous nature allows the warming sun to penetrate during the winter. There are too many other high-quality trees in this cruel world to warrant planting this tree.
Scientific name: Albizia julibrissin
Pronunciation: al-BIZ-zee-uh joo-lih-BRISS-in
Common name(s): 'Alba' mimosa tree, 'Alba' silktree
USDA hardiness zones: 6B through 9B (Figure 2)
Origin: not native to North America
Invasive potential:According to the IFAS Assessment of Non-Native Plants in Florida's Natural Areas (IFAS Invasive Plant Working Group 2008), Albizia julibrissin 'Alba' is invasive and not recommended in Florida.
Uses: reclamation; deck or patio; specimen
Availability: not native to North America
Height: 15 to 25 feet
Spread: 25 to 35 feet
Crown uniformity: irregular
Crown shape: vase, spreading
Crown density: open
Growth rate: fast
Leaf arrangement: alternate (Figure 3)
Leaf type: bipinnately compound, odd-pinnately compound
Leaf margin: entire, ciliate
Leaf shape: oblong, lanceolate
Leaf venation: pinnate
Leaf type and persistence: deciduous
Leaf blade length: less than 2 inches
Leaf color: green
Fall color: no color change
Fall characteristic: not showy
Flower color: white/cream/gray
Flower characteristics: showy
Fruit shape: elongated
Fruit length: 3 to 6 inches
Fruit covering: dry or hard
Fruit color: brown
Fruit characteristics: does not attract wildlife; showy; fruit/leaves a litter problem
Trunk and Branches
Trunk/bark/branches: branches droop; not showy; typically multi-trunked; thorns
Pruning requirement: needed for strong structure
Breakage: susceptible to breakage
Current year twig color: gray
Current year twig thickness: very thick
Wood specific gravity: unknown
Light requirement: full sun
Soil tolerances: sand; loam; clay; acidic; slightly alkaline; well-drained; occasionally wet
Drought tolerance: high
Aerosol salt tolerance: moderate
Roots: can form large surface roots
Winter interest: no
Outstanding tree: no
Ozone sensitivity: unknown
Verticillium wilt susceptibility: resistant
Pest resistance: sensitive to pests/diseases
Use and Management
Growing best in full sun locations, mimosa is not particular as to soil type but has low salt-tolerance. Grows well in acid or alkaline soil. Mimosa tolerates drought conditions well but has a deeper green color and more lush appearance when given adequate moisture. The litter problem of the blooms, leaves, and especially the long seed pods requires consideration when planting this tree. Also the wood is brittle and has a tendency to break during storms though usually the wood is not heavy enough to cause damage. Typically, most of the root system grows from only two or three large-diameter roots originating at the base of the trunk. These can raise walks and patios as they grow in diameter and makes for poor transplanting success as the tree grows larger.
Unfortunately, mimosa (vascular) wilt is becoming a very widespread problem in many areas of the country and has killed many roadside trees. Despite its picturesque growth habit and its beauty when in bloom, some cities have passed ordinances outlawing further planting of this species due to its weed potential and wilt disease problem.
Several other cultivars exist: 'Rosea' ('Ernest Wilson') has bright pink flowers, is hardier than the species, and is 10 to 15 feet in height; 'Rubra' has deep pink flowers. 'Charlotte', 'Tyron', and 'Union' are reportedly wilt resistant and might be coming into production in selected nurseries in some areas.
Mimosa readily germinates from its abundant seeds but the wilt resistant trees must be increased by root cuttings.
Problems include cottony cushion scale, mites, and mimosa webworm.
Mimosa (vascular) wilt is quite a problem and is fatal. It can spread to adjacent mimosas by root grafts.
Fox, A.M., D.R. Gordon, J.A. Dusky, L. Tyson, and R.K. Stocker. 2008. IFAS Assessment of Non-Native Plants in Florida's Natural Areas: Status Assessment. http://plants.ifas.ufl.edu/assessment/pdfs/status_assessment.pdf (November 16, 2012)