The Rhododendrons
RHODODENDRON - Lovely White Rhododendron
Rhododendron is a very large genus – NO KIDDING - about 1,024 species!They are in the heather family (Ericaceae) - either evergreen or deciduous. Most are native to eastern Asia and the Himalayan region. Because of their spectacular flowers they are grown in every corner of the planet !Their name comes from the words RED TREE - referring to its flowers. These can be scented or not and actually occur in a wide range of colors—white, yellow, pink, scarlet, purple, and blue.Ranging in habit from evergreen to deciduous as well as low-growing ground covers to tall trees. Some are mat like dwarfs only 4 inches high, while others are trees in excess of 40 feet.Leaves are thick and leathery and are evergreen in all but the azalea species, some of which are deciduous.
Big bold and beautiful !
Azaleas are a subgenera and are distinguished from "true" rhododendrons by having only five anthers per flower.
Care
Like other ericaceous plants, most prefer acid soils with a pH of roughly 4.5–5.5. This means they require an acid fertilizer applied regularly. Monthly if the plant is containerized and being watered via automatic irrigation. Otherwise they can get chlorotic !
Chlorosis caused by alkaline soil
Some are tolerant of semi shade but most prefer full sun. Azaleas tend to be more tolerant of a shady spot but tend to become thinner and with fewer leaves.Rhododendrons have fibrous roots and prefer well-drained soils high in organic material. Doing poorly in non-draining or alkaline soil.Don't let them ever totally dry out as they may get stunted for an entire season if this happens. Their natural habit is an evenly moist soil - think the edge of a bog !
Diseases
Major diseases include Phytophthora root rot. This is directly related to poor draining soil as this fungus prefers stagnant soil.Stem and twig fungal dieback is common in wet springs when the buds are opening. Cold dry winter winds and a late spring frost will damage buds as well.
blackened roots from Phytophthora
Rhododendron bud blast, a fungal condition that causes buds to turn brown and dry before they can open, is caused by the fungus Pycnostysanus azalea.It is very specific and only brought to the plant by the rhododendron leafhopper. Insect control in Spring is very important to reduce the risk of this disease.
bud blast
Groups
There are 1000 + species - horticulturally, these are divided into the following groups.
Evergreen Rhododendrons
- Large group of evergreen shrubs that vary greatly in size- Most flowers are bell-shaped and have 10 stamens.
bubblegum pink !
Vireya (Malesian) Rhododendrons
- Tender shrubs from the tropics
Beautiful - looks like a Clivia !!!!!!
Azaleas
- Shrubs with smaller and thinner leaves than evergreen Rhododendrons- Funnel-shaped flowers that usually have 5 stamens
Deciduous hybrid Azaleas
Deciduous Orange Azalea
Evergreen hybrid Azaleas
Common greenhouse Azalea
Azaleodendrons
- semi-evergreen hybrids between deciduous Azaleas and Rhododendrons- Hybrids between the Japanese azalea R. japonicum and hardy Rhododendrons
What's a garden without a Rhododendron !
Or an Azalea !!!!!!!!!!
How about some in your garden !
Call us - we can plant some for you !
PLANT SPECIALISTSGREENING NEW YORK FOR OVER 53 YEARS !
Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBAAll photographs used with permission @SHUTTERSTOCK