Albizia

( al - BIZ - ee - uh )

At-A-Glance Information

This genus of fast-growing tropical and sub-tropical trees and shrubs is native to Asia, Africa, Madagascar, America, Australia, and the Old World Tropics. These evergreen and deciduous trees are commonly called Silk Plants, Silk Trees, Albizzias, East Indian Walnuts, or Sirises. Silk trees are easily identified by their lofty, fern-like foliage and beautiful, profuse shows of brush-type flowers. Grow Albizzias as specimens, street trees, pollinator magnets, or in containers. Take care when planting these trees in the landscape, as leaves and seeds are toxic to animals if ingested.

albizia species and varietals

The genus Albizia includes around 160 species and is a member of the plant family Fabaceae. The genus is named for the Italian nobleman Filippo degli Albizzi. The growing zones for these trees vary somewhat depending on the species, though most will tolerate the climate in USDA hardiness zones 6-9 or Sunset growing zones 4-23. To find your zone, click here: Zone Map.

Albizia adianthifolia (Flat-Crown, West African Albizia, Rough-Bark Flat-Crown, Platkroon)
This species of Silk Tree is native to South Africa through Tropical Africa, and forms a large, deciduous tree reaching upwards of 82 feet tall at maturity. Foliage is dense and bright green, and fragrant flowers are fluffy and white to cream-colored, produced in late winter and springtime. These trees are widely cultivated as ornamentals, though they are profuse re-seeders, especially in sandy soils. USDA zones 9-11.

Albizia amara (Krishna Siris, Oil Cake Tree, Bitter Albizia)
This mid-sized, deciduous tree is native to Sudan, Ethiopia, India, and Sri Lanka, and has grainy, scaly grey bark. These trees resemble Acacias, but have no thorns. Flowers are white to yellow powder-puffs and bloom in springtime. These trees are intolerant of shade and drought-resistant. Bitter Albizias have medicinal uses and are also harvested for their wood, which is popular in construction and furniture-building.

Albizia chevalieri (Kalkora Mimosa)
These plants form shrubs or small trees that top out around 23 feet tall with open, spreading crowns. Foliage is grey-green and corky bark is pale grey to tan with deep fissures. Leaves are grey-green and flowers are reddish with white edges. Seed pods follow blooms. This species is best in USDA hardiness zones 9a-11b.

Albizia chinensis (Chinese Albizia, Chinese Silk Tree, Kala Siris, Sau Tree, Siris, Sirwal, Kalik Siris)
This species can be deciduous or evergreen depending on where it is grown and how much protection it has, and forms a tree that reaches 140 feet tall. These trees are a favorite forage plant of goats in their native range (India, China, and Indonesia). Foliage is green and ferny and brush-like flowers are white with red tips. Chinese Albizia does well in USDA hardiness zones 9-11.

Albizia julibrissin (Mimosa, Persian Silk Tree, Pink Siris, Nemu Tree, Bastard Tamarind, Japanese Mimosa, Silky Acacia)
This species of deciduous tree needs full sun to partial shade and regular water for best performance. It has an open growing habit, and reaches 40 feet tall with a canopy spreading out to around 70-80 feet wide. Leaves are fern-like and light sensitive, folding in on themselves at nighttime. Flowers are fluffy and pink. These trees are most attractive when grown as multi-trunk trees, but can also do well as a singular-trunked plant. The specific epithet julibrissin refers to the Persian word for silk flower (gul-i-abrisham). These trees do well in USDA hardiness zones 6-10.

Albizia lebbeck (Indian Siris, Broome Raintree, East Indian Walnut, Lebbeck, Frywood, Koko, Woman's Tongue Tree, Vaagai)
This species reaches between 60 and 100 feet tall and produces very fragrant white to cream-colored or yellowish flowers. Fruit pods follow blooms. These trees are used for medicinal purposes as well as timber in their native range (Myanmar and the Indian subcontinent). Good in USDA hardiness zones 9a-11b.

Albizia odoratissima (Kali Siris, Black Siris, Ceylon Rosewood, Fragrant Albizia, Kaadu Baage, Chinchava)
Known as one of the best nitrogen-fixing trees, this species is native to India, Bangladesh, Bhutan, Nepal, Myanmar, Laos, Thailand, Vietnam, and Sri Lanka. These are fast-growing trees, putting on about 3 feet annually, and are commonly seen between 50 and 80 feet tall at maturity. Foliage is dark green, and flowers are fragrant and white, fading to a pale orange with age. Bark is dark grey. These trees grow well in USDA hardiness zones 9a-11b.

Albizia procera (Tall Albizia, White Siris, Karoi Tree, Forest Siris, Safed Siris)
This species of large trees is native to southeast Asia and India, and is normally seen reaching between 23 and 50 feet tall, though some specimens have been recorded at 100 feet tall, hence the common name 'Tall Albizia'. The Latin specific epithet also refers to the towering height of these trees (procerus = very tall or high). These trees lose their leaves during the dry season of the year, and bark is smooth and light-colored. Puffball flowers are greenish-yellow. Tall Albizia grows well in USDA hardiness zones 10-12.

Caring for Albizia

These trees do best in areas where summers are hot, and with regular water will grow quickly to their maximum height. Start with a tree grown from container that is at least a year old. Plant Mimosa trees in full-sun exposure (they should receive between 6 and 8 hours of full sun each day to perform well). Ensure that soil is well-draining, and that it has a pH of between 4.6 and 5.0 (slightly acidic to neutral). Amend soil before planting with plenty of organic matter to give the tree a head-start in the garden. Mulch around the base of the plant to increase soil moisture retention and suppress weed growth. Avoid piling the mulch against the trunk, as this will lead to rotting diseases. Keep the soil consistently moist as trees establish themselves. At maturity, these trees can be drought-tolerant, but do prefer regular waterings especially during periods of the year that are dry and hot.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Prune to shape and remove dead, damaged, or diseased foliage. Pruning is best done in late winter or early springtime, just before new growth pushes out for the year. In cooler climates, these trees may need some additional protection from frost. Consider wrapping the trunk with a burlap covering or provide other winter protection in these areas. These are commonly short-lived ornamental trees, with an average lifespan of about 30 years.

Growing Albizia in Containers
Albizia trees can be grown either directly in the garden soil or in containers. Choose a large container that is about 3-4 inches larger than the nursery pot. Ensure that the container has adequate drainage holes on the bottom. Fill with well-draining soil amended with plenty of organic material and perlite, and cover the top of soil with a layer of mulch to increase soil moisture retention, insulate roots and suppress weed growth. Place the container in an area that receives full sun (between 6 and 8 hours each day). Albizia trees grown in containers will need more frequent waterings than their in-ground counterparts. As a general rule of thumb, water whenever the top inch or two of soil feels dry to the touch. Pot trees up when necessary.

Propagation

Albizias, or Silk Trees, can be propagated either by using cuttings or from seed. To ensure that your propagated tree will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your tree, follow the instructions below:

Propagating Albizia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about 3-4 weeks have passed, the cutting should be rooted.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home in the landscape. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new tree.

Propagating Albizia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds in fall. The seed pods on these trees are pretty easy to spot, they're large and dangle from the branches, left behind after flowers have faded. Once they have dried out and begun to split open, cut them off of the tree, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to release the seeds. Once they have been released, take them out of the bag and put them in an airtight container in a cool, dark, dry area. Properly stored seeds can stay viable for five years or more.
In spring, bring the seeds out. The seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get a tree with desirable traits. Place your seeds in a bowl and pour almost-boiling water over them. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float. Leave the seeds in the water for 24 hours.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds about a quarter inch to a half-inch under the soil surface. Cover them with soil and water them in. Place seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet as it continues to grow. Keep it in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home in the landscape.