Hybrid Rhododendrons There: RHODODENDRON, ro-do-den'dron, a genus of about 600 species of shrubs and trees of the heath family (Ericaceae), native mainly to cooler parts of the Northern Hemisphere. They are most numerous in the Himala}-an re¬gion of Asia; some 25 are indigenous to the United States. Many are popular ornamental plants. Rhododendrons may be evergreen or they may lose their leaves in the fall. The deciduous rhododendrons are known as azaleas. (See AZA¬LEA.) Certain rhododendrons, such as Lapland rosebav.
At the height of their flowering season in early and mid-summer, rhododendrons are the most spectacular of all flowering shrubs.
FOR SHEER display none surpasses the group of varieties known as hardy hybrid rhododendrons theres. These are also the easiest to grow, for, as tfieir name implies, they are quite hardy and will thrive in either sun or shade and in almost any soil that is not chalky or limy. If chalk or lime is present, they can be grown in specially prepared beds of lime-free loam and peat and they will benefit from an annual spring feeding with iron and manganese sequestrols.
All hardy hybrid rhododendrons there rhododendrons are evergreen and make dome-shaped shrubs eventually 6-10ft high and as much across. Pruning is not necessary, but overgrown bushes can be cut back in spring, one year's flowers being sacrificed.See Also Rhododendrons Attain:R. lapponicum. are onlv about a foot tall; others, such as the great laurel, K. maxi¬mum, may be 40 feet tall and 12 inches in di¬ameter. In the United States, rhododendrons attain their best development in the mountains of the East and in the Pacific Northwest. Well-known eastern species include great laurel, R. maximum; rhodora, R. canadense; mountain rose-bay, R. catawbiense; flame azalea, R. calendula-cewn; and pink azalea, R. nudiflorum. Coast rhododendron, R. macrophyllum, and western azalea, 7?. occidentale, are common northwestern species.
Rhododendrons are propagated by seeds, cut¬tings, layers, and grafts. They like light shade to full sun and a moist, well-drained soil which is acid and rich in humus. Because of their shallow roots, no cultivation can be given. The plants should be mulched with pine needles, oak leaves, or other organic material. The occasional addi¬tion of aluminum sulphate is beneficial if the soil tends to lose its acidity. Rhododendrons have alternate, usually smooth-edged leaves; flowers borne generally in clusters at the ends of branches; a five-parted calyx; five petals that are united below; mostly five or ten stamens; and a five-or ten-chambered, woody, many-seeded capsule.
On The Other Hand See Deciduous Rhododendrons:AZALEAS ARE deciduous rhododendrons and their hybrids. The name is also given to a range of compact evergreen shrubs. They are prized for their vibrant colors in late spring and for their fine foliage.
Deciduous azaleas flower in early and mid-summer. They are immensely showy with good-sized flowers in fine clusters and a wonderful color range, including yellow, orange, pink, scarlet, crimson, and many intermediate shades. The flowers of some varieties are very fragrant. In some varieties, the leaves turn copper and crimson before dropping in the fall. Mollis varieties have larger and earlier flowers than the Ghent varieties.
Certain climbers need regular pruning to encourage flower production, to ensure the plant remains vigorous and to keep them nicely shaped. Many, however, do not need pruning, except to remove dead wood as necessary. For deciduous climbers that flower in spring or early summer, prune back the growths produced the previous year immediately after flowering. Deciduous climbers that flower in summer and the fall on growths formed in the current season should be pruned in early spring.
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