The ornamental Kwanzan flowering cherry tree (Prunus serrulata "Kwanzan") adds show-stopping beauty to almost any garden or landscape. In the spring, the tree grabs attention with a profusion of pink blossoms. In the fall, the leaves turn shades of yellow to orangish-bronze before falling off to reveal a beautiful trunk and branch structure that brightens winter gardens.
Named after a mountain in Japan called Sekiyama, Kwanzan flowering cherry trees are native to China, Japan and Korea. The trees became well known in the United States when Japan gave a gift of more than 3,000 flowering cherry trees to the United States in 1912. Of those original trees, the Kwanzan now dominates the cherry trees around the Washington, D.C. area. Originally, the Kwanzan cherry trees were planted along the Potomac River from the Lincoln Memorial all the way to East Potomac Park. While few of those trees now exist, recently planted Kwanzan cherry trees grow all over the city.
Kwanzan flowering cherry trees put on a great show each spring when clusters of large double-pink blossoms resembling carnations cover the tree in mid-to-late April. The beautiful pink flowers tend to last longer than those of other flowering cherry trees. Once the flowers fade, green leaves with a tinge of red pop out, turning dark green in the summer. In the fall, the leaves turn beautiful shades of yellow, orange and gold. Once the leaves fall off in late fall, the shiny, gray bark of the tree and its twisted branches become apparent. The tree grows up to 30 feet in height and a bit wider at maturity.
Kwanzan thrives in U.S. hardiness zones 5 to 9. The deciduous tree grows best in full sun in moist soil. It also grows in alkaline soil if well-drained. Plant Kwanzan in the spring after all danger of frost has passed. After planting, water the tree thoroughly and continue to water it every few days for the first few weeks. While Kwanzan trees tend to be somewhat drought tolerant, water the tree regularly after it gets established.
Kwanzan trees remain highly susceptible to pests, limiting their lifespan to 15 to 25 years. Aphids attack the tree, distorting new growth and contributing to unsightly mold spots. Borers also attack the tree although regular fertilizer applications help eliminate the problem. Spider mites cause yellowing of the leaves, while tent caterpillars create large webby bags that contain hundreds of caterpillars who eat the leaves. The webs of the tent caterpillars need to be manually removed and destroyed.
Bacteria sometimes causes leaf spot and twig cankers on Kwanzan cherry trees. Once these small, reddish spots dry up, they fall out, leaving holes in the leaf. Black knot also causes problems by causing the branches to swell. These branches need to be pruned from the tree to help contain the problem.