Rhododendron are found mainly in Asia, although it is also widespread throughout the highlands of the Appalachian Mountains of North America. It is the national flower of Nepal as well as the state flower of West Virginia and Washington.
Rhododendron and Azalea are now placed together in the genus Rhododendron. It is a genus of about 1000 species in the Ericaceae family and was described by Carl Linnaeus in 1753. The name “azalea” is commonly used for native deciduous species and many evergreen hybrid types. Generally “rhododendron” is used for those species that have large, evergreen, leathery leaves and flowers distinctly clustered in terminal groups. When a sharp division cannot be made, it is always correct to call any of them rhododendrons.
IDENTIFY RHODODENDRON AND AZALEA PLANT
Rhododendron and Azalea are found mainly in Asia, although it is also widespread throughout the highlands of the Appalachian Mountains of North America. It is the national flower of Nepal as well as the state flower of West Virginia and Washington in United States, and state tree of Sikkim and Uttarakhand in India.
They are evergreen or deciduous shrubs and small to large trees with various hairs, and/or with peltate scales or glabrous, indumentum sometimes detersile (the hairs tangled and coming away as a layer) with spirally arranged 1–2 cm to over 50 cm leaves. The leaves sometimes clustered at stem apex; margin entire, very rarely crenulate, abaxial indumentum sometimes with a pellicle (a thin skin like layer on the surface). Throughout the summer and fall the leaves add a pleasing, deep‑green color to the garden. Some deciduous azaleas add bright fall color before the leaves drop.
The plants from this genus bloom in late winter through to early summer from a raceme or corymb inflorescence, mostly terminal, sometimes lateral, few- to many-flowered, sometimes reduced to a single flower. Most species have brightly coloured flowers. In addition to being renowned for its beauty, the Rhododendron and Azalea are also highly toxic - it contains andromedotoxins in both its leaves and nectar, including honey from the nectar.
Both species and hybrid rhododendrons (including azaleas) are used extensively as ornamental plants in landscaping in many parts of the world, including both temperate and subtemperate regions. Many species and cultivars are grown commercially for the nursery trade. In the Indian state of Himachal Pradesh, rhododendron flowers have been used for some time to make popular fruit and flower wines.
RHODODENDRON AND AZALEA PLANT CARE AND CULTURE
Cultural information should only be used as a guide, and should be to be adapted to suit you. Your physical location; where you grow your plants, how much time you have to devote to their care, and many other factors, will need to be taken into account. Only then can you decide on the cultural methods that best suit you and your plants.
Light:
Rhododendron need ample protection from wind and direct afternoon sun. Do not plant them in windy spots. Around buildings, they do best on the east or north side. In open areas, they like alternating sun and shade. Plants may survive continuous shade if trees have branches pruned high. Fences, shrubbery, or screens may also give protection from afternoon sun. Some deciduous azaleas are less sensitive to sun, and should be used if the location receives full afternoon sun. However, in full sun delicate flower colors will bleach quickly even though the plants may grow well.
Temperature:
In spring and summer, the ideal temperature for growth is 18–22 ° C. In autumn and winter, these plants goes to a rest period which last 1.5 - 2 months with a temperature of 12–15 ° C. Winter damage may occur at infrequent intervals, usually due to lack of dormancy in the plant when cold weather occurs. To help development of winter hardiness, avoid adding large amounts of nitrogen after July. Some factors affecting the ability of a plant to withstand cold temperatures are length of exposure to low temperatures, rate of temperature fall, extent of plant dormancy, wind and sun exposure, overall condition of the plant, and plant variety.
Substrate and growing media:
Soils should be well drained and should contain an abundance of organic matter. The addition of leaf mold, peat moss, or other organic matter will help almost all soils. Most of these plants prefer acid soils with a pH of roughly 4.5-5.5; some tropical Vireyas and a few other rhododendron species grow as epiphytes and require a planting mix similar to orchids. When planting, dig a hole twice the size of the root ball. Mix the excavated soil with soil amendments and place enough improved soil in the bottom of the hole so the top of the root ball is slightly higher than the surrounding soil. Fill the hole to the top, watering as you fill to settle the soil and eliminate air pockets. Allow the plant to establish itself in the new location before adding any fertilizer.
Rhododendron and Azalea, when properly grown, can be transplanted successfully at any time of year if they are given special care in watering and protection from drying and freezing. The ideal time to transplant these plants is during their dormant season, either in the fall or early spring while temperatures are cool and soil moisture is plentiful. Plant azaleas or rhododendrons at the same depth they were growing in the nursery. Spacing will depend on the mature spread of the plants.
Watering:
Rhododendron and Azalea have shallow, fibrous root systems, so provide ample water during the summer. If they are planted under wide eave overhangs, furnish water during the entire year. Keep in mind that although these plants need moisture, they will not thrive in wet, poorly aerated soils.
Use mulches to control weeds, conserve moisture, and provide more uniform soil temperatures. Mulches can be made of sawdust, bark dust, peat moss, straw, or other organic materials. If these materials are incorporated into the soil after serving as a mulch, add some nitrogen to assist in decomposition of the woody materials.
Avoid excessive irrigation in fall. Plants kept dry in September will tend to harden off and be better prepared for the winter. If the fall has been excessively dry, watering should be done after the first killing frost. At that time watering will not reduce winter hardiness but will prepare the plant for winter. The soil should be thoroughly moist before cold weather sets in. The best time for fall watering is about Thanksgiving.
Fertilizer:
Avoid the excessive use of lime or alkaline fertilizers around azalea and rhododendron plants. If necessary, apply nitrogen fertilizers or mixtures (either organic or inorganic) containing nitrogen, phosphorus, and potassium soon after flowering in the spring. Relative merits of an organic fertilizer as compared to a chemical fertilizer depend on whether the slow availability and less frequent application of the organic type can justify the extra cost. A light application of a fertilizer formulated for acid‑loving plants may be added to the surface before the mulch is applied.
Fertilizing should be done in April or May, but don’t fertilize after July. Late summer fertilization may force out tender fall growth that will be killed by the winter.
Pruning:
If new plants are selected properly, taking into consideration mature plant size and space to be filled, little pruning should be necessary. Remove dead and injured branches. If pruning is necessary, prune the plants soon after flowering to allow flower bud formation for the following year. “Dead-heading” is a pruning operation that involves removing spent flower clusters. It should be done annually.
Azaleas sometimes branch poorly and form a loose, open shrub. The plants’ form can be improved by pinching out the soft, new shoots of vigorous growing plants. Do not pinch after July because flower buds will not have time to develop for the following year.
Propagation:
Deciduous Azalea are propagated commercially by seed. Evergreen Azalea and Rhododendron root quickly (6 to 8 weeks) from softwood or semi-hardwood tip cuttings. Cuttings may be made at any time, but June to July cuttings seem most ideal for rooting azaleas, and August to September cuttings seem best for rhododendrons. Make cuttings 3 to 4 inches long, remove lower leaves, and place the cut end in rooting medium. Equal parts of peat moss and clean sharp builder’s sand make an ideal rooting medium. After roots are formed, place the plants in pots or in a protected area and keep well watered.
BUY RHODODENDRON AND AZALEA PLANT AND RELATED PRODUCTS
SOME SPECIES AND VARIETIES OF THODODENDRON AND AZALEA WITH CARE TIPS AND CULTURE SHEET:
- Rhododendron alabamense - Alabama azalea - Azalea alabamensis
- Rhododendron arborescens - Sweet Azalea - Azalea arborescens
- Rhododendron arboreum - Tree rhododendron
- Rhododendron atlanticum - Dwarf azalea - Azalea atlantica
- Rhododendron austrinum - Florida Azalea - Orange Azalea - Florida Flame Azalea
- Rhododendron bureavii - Bureau rhododendron
- Rhododendron calendulaceum - Flame azalea - Azalea calendulacea
- Rhododendron calophytum - Beautiful-face rhododendron
- Rhododendron canadense - Rhodora - Canada rosebay
- Rhododendron canescens - Piedmont azalea - Mountain azalea - Azalea canescens
- Rhododendron catawbiense - Catawba rosebay
- Rhododendron caucasicum - Georgian snow rose
- Rhododendron cumberlandense - Cumberland azalea - Azalea cumberlandensis
- Rhododendron davidsonianum - Concave-leaf rhododendron
- Rhododendron decorum - Great white rhododendron
- Rhododendron eastmanii - May white azalea
- Rhododendron edgeworthii
- Rhododendron English Roseum
- Rhododendron falconeri - Falconer rhododendron
- Rhododendron flammeum - Oconee azalea - Azalea calendulacea var. flammea
- Rhododendron fulvum - Cinnamon-coloured Rhododendron
- Rhododendron impeditum - Dwarf Purple Rhododendron
- Rhododendron luteum - Yellow azalea - Honeysuckle azalea - Sweet pontica azalea
- Rhododendron macrophyllum - Pacific Rhododendron
- Rhododendron maddenii
- Rhododendron megacalyx
- Rhododendron Nova Zembla
- Rhododendron occidentale - Western azalea - Azalea occidentalis
- Rhododendron pendulum
- Rhododendron Percy Wiseman
- Rhododendron periclymenoides - Pink azalea - Pinxterbloom azalea - Pinxter-flower
- Rhododendron PJM Elite Star
- Rhododendron prinophyllum - Early azalea - Roseshell azalea - Azalea prinophylla
- Rhododendron prunifolium - Plumleaf azalea - Azalea prunifolia
- Rhododendron Roseum Elegans
- Rhododendron seinghkuense
- Rhododendron simsii - Indoor Azalea
- Rhododendron viscosum - Swamp azalea - Clammy azalea - Swamp honeysuckle
- Rhododendron yakushimanum - Yak Rhododendron
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