Rhododendron arboreum Sm.
Rhododendron arboreum var. arboreum, Rhododendron puniceum, Rhododendron windsorii
Color: Red, pink or white
Bloom Time: Early and mid-spring
Rhododendron arboreum is the national flower of Nepal, in India it is the state tree of Uttarakhand and the state flower of Himachal Pradesh and Nagaland. Its name means "tending to be woody or growing in a tree-like form." It has been recorded as reaching heights of up to 66 feet (20 m), although more usually it has a height and spread up to 39 feet. This plant holds the Guinness Record for World's Largest Rhododendron. In early and mid-spring, trusses of 15 to 20 bell-shaped flowers, up to 2 inches (5 cm) long and wide, are produced in red, pink, or white. They have black nectar pouches and black spots inside.
USDA hardiness zone 7b to 10b: from 5 °F (−15 °C) to 40 °F (+4.4 °C).
How to Grow and Care
Once properly located in the planting bed, water thoroughly and cover with an organic mulch, which will break down to supply nutrients as it decomposes. A pine bark covering applied at 2 inches (5 cm) is thought to inhibit fungi that cause root rot. Do not mulch with peat moss, as it is difficult to rewet after it has dried out. Proper mulching will decrease the need for future care.
Rhododendron care includes yearly fertilization, which is best applied in fall, following a hard freeze or in early spring. Use fertilizer for acid-loving plants, such as organic cottonseed meal. The organic material you have worked into the soil previously will break down to provide some of the necessary nutrients.
Consistently moist soil is needed for proper care, but too much water creates problems for the growing Rhododendron. When leaves curl and twist, this indicates that water is needed immediately. The Rhododendron bush should not be allowed to go through the stress of wilting. See more at How to Grow and Care for Rhododendron.
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