Albizzia is a group of quick-growing, popular flowering trees, grown in the southern and western parts of the U.S. Albizzias are natives of Persia, Japan, and other Eastern countries and in Australia. A. Julibrissin, commonly known as Mimosa or Silk Tree, can reach a height of 30-40 feet. The foliage is feathery, resembling a fern's and their leaflets fold together at night. The 5- to 8-inch fluffy clusters of pink flowers are produced all summer long and are very attractive to hummingbirds. A. Julibrissin's variety rosea only grows from 15 to 20 feet high and has smaller clusters of darker pink flowers; it is also slightly more cold resistant. A. lophantha is the next hardiest. It will grow 10-12 feet tall, but can be kept much smaller by pruning every spring before new growth begins. If this is done, however, not many flowers, which are yellow, will be produced. These plants are suitable for use in summer flowerbeds because of their pretty foliage.
Mimosa trees can be grown outdoors in mild climates only. They grow best in full sun and well-drained soil, but will tolerate partial shade and poor soil, including alkaline soil. Young trees that aren't over 8 to 10 feet should be bought balled and burlapped in the spring. If your climate gets cool in the winter, wrap the trunk of your newly planted Mimosa in burlap or heavy paper for a few years until they become established. If they are grown in a greenhouse, they should be potted in March in loam and leaf mold with an addition of sand. A bit of peat moss would also be beneficial. March is when they should be repotted if they need larger containers. Pruning should be done in the winter or early spring.
Seeds are the easiest way to increase your plants. They are very hard so they need to be soaked in warm water for twelve hours before planting in February, in a greenhouse having a minimum temperature of 50 degrees. Cuttings that are 1½ to 2 inches long can be made from the ends of young side shoots. They're inserted in sandy soil in partial shade in the summer and are covered with a bell jar or hand light until rooted. This takes four to five weeks. The rooted cuttings are potted separately in small pots and kept in a greenhouse for the winter. When they start to outgrow the greenhouse, they should be severely pruned in early spring. The plants will soon start to grow again. Mimosas often have several trunks; while they are young, train them to grow with a single trunk by pruning out the extras.