Rhododendron catawbiense all about growing caring scientifically

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Classification:

Kingdom:     Plantae

(unranked):  Angiosperms

(unranked):  Eudicots

(unranked):  Asterids

Order:         Ericales

Family:        Ericaceae

Genus:        Rhododendron

Subgenus:    Hymenanthes

Species:          R. catawbiense

Symbol:         RHCA8                   

Group:           Dicot   

Family:           Ericaceae      

Duration:           Perennial             

Growth Habit:    Tree Shrub              

Native Status:          L48 N

                      

Wiki:

Rhododendron catawbiense (Catawba Rhododendron) is a species of Rhododendron native to the eastern United States, growing mainly in the Appalachian Mountains from Virginia south to northern Alabama.

It is a dense, suckering shrub growing to 3 m tall, rarely 5 m. The leaves are evergreen, 6-12 cm long and 2-4 cm broad. The flowers are 3-4.5 cm diameter, violet-purple, often with small spots or streaks. The fruit is a dry capsule 15-20 mm long, containing numerous small seeds.

The species is named after the Catawba tribe of Native Americans.

Cultivation and Uses

It is a popular ornamental plant, both in North America and also in Europe, grown for its spring flower display. Outside of its native range, it is naturalized locally north to Massachusetts.

It is very closely related to (and very difficult to distinguish from) the European species Rhododendron ponticum, and hybridizes readily with it in cultivation; the hybrid is invasive in parts of northeastern. Scotland in areas too cold for typical R. ponticum to thrive (Milne & Abbott 2000); the presence of this hybrid was only determined by genetic analysis.

Backyard gardener:

Boursault is a sturdy, hardy shrub, to -25 degrees Fahrenheit, bearing sizable lavender flowers held in round trusses. Shrubby, evergreen "ironclad" rhododendron with medium leaves. Grows to 5 feet tall.

There are between 500 and 900 species of evergreen and deciduous plants in the Rhododendron genus. Azaleas fall into this category. The evergreen rhododendron is characterized by medium to long, elliptical leaves and large, clustered, trusses of, late, showy, spring to early summer flowers, ranging in colors from red, pink, white, lavenders, purples and even yellow and orange. Form maybe low and mounding to gangly and almost tree-like with age.

All rhododendrons love well-drained, acid soil and should be planted high, preferably on raised beds. Partial shade is preferable too, though many plants grow quite well in full sun in cooler, more forgiving climates. In general, the evergreen rhododendron tends to do better in cooler areas of zone 7 and lower, thriving in the Appalachian Mountains and the Pacific Northwest.

Different Characteristics:

Habitat

• native to southern Appalachian mountains from Virginia through Georgia
• zone 4

Habit and Form

• an evergreen shrub
• typically 6' to 10' tall with an equivalent spread
• can get to 20' tall
• mounded to upright in habit
• generally dense under ideal conditions, but becomes more open in dense shade or in unfavorable sites

Summer Foliage

• alternate leaves, clustered towards the shoot apex
• evergreen, elliptical leaves
• 3" to 6" long and 1" to 2" wide
• color is dark green
• leaves quite leathery

Autumn Foliage

• no fall color
• evergreen

Flowers

• large flower buds at the shoot apex
• lilac-purple to magenta color with green or orange-speckled throat
• individual flowers are 2.5" across and funnel-shaped
• flower clusters are 5" to 6" in diameter and comprised of 5 to 10 flowers
• blooms in mid to late May
• quite showy in bloom

Fruit

• dehiscent capsule
• not ornamentally attractive

Bark

• gray-brown
• not often highly visible through evergreen foliage

Culture

• partial shade to full sun
• prefers moist, cool, acidic, well-drained, organic soil
• avoid dry, hot windswept sites
• removal of spent blossoms encourages new growth and flower bud set
• transplant from containers or B&B.

Landscape Use

• as a specimen
• in groups or massed
• shrub border
• woodland setting
• useful in partially shaded areas
• for decoration from both flowers and foliage

Liabilities

• black vine weevil
• phytophthora root rot
• desiccation in dry, windswept, sunny locations
• chlorosis on high pH soils

ID Features

• broadleaf evergreen
• large, showy flowers
• flower bud dramatically larger than vegetative buds
• leaf-like subtending bracts do not surround the flower bud as in R.maximum
• leaves large, clustered at end of shoot in an alternate arrangement

Propagation

• by seed
• by stem cuttings in late summer, fall and winter
• tissue culture for selections and new hybrids

Cultivars/Varieties

Often, the large-leaf rhododendrons are all grouped together under the heading R. catawbiense for convenience. This organization gives the impression that these dozens/hundreds of cultivars are all selections or hybrids of this species. In fact, most are complex interspecific hybrids and many contain no R. catawbiense blood. The varieties and cultivars listed below are either selections of R. catawbiense or F₁hybrids (first generation) with R. catawbiense. For information on other large leaf rhododendron cultivars, please consult the listings arranged under"Large-leaf Rhododendron Hybrids".

var. album - The white flowers of this selection open from buds that are tinged lilac. This form features dark green foliage. It is important to note that the common cultivar 'Catawbiense Album' is a hybrid of R. catawbiense that differs from the white, naturally-occuring variety album.

var. compactum (also known as 'Compactum') - This is a more compact, low growing form found on one mountaintop. It only grows to about 3' tall.

'Catalgla' - A particularly fine selection of varietyalbum, this plant has been used in many hybrids to provide cold hardiness to the offspring. It is very cold hardy to -25 F.

'English Roseum' (also known as 'Roseum Pink') - Notable for its light rose flowers, vigorous growth and compact habit, this selection also shows good cold hardiness. It is a dependable mainstay of New England gardens. It is probably a hybrid.

'Grandiflorum' - Hardy to -25 F with distinctive lilac-colored flowers, this selection also displays attractive plant habit. It is probably a hybrid of R. catawbiense.

'Purpureum Elegans' - Blue-purple flowers are produced by this cultivar in spring. It shows good cold hardiness and plant habit. It is probably a hybrid.

'Roseum Elegans' - The flowers of this popular cultivar are rose-like and somewhat small. It is a vigorous grower with good habit. This cultivar has become a mainstay in New England gardens -- probably the most common selection. The plant is very dependable and probably a hybrid. Some horticulturists criticize its monotonous use and rather brash flower color.

How to grow this Plant (Backyard gardener):

Characteristics

Cultivar:                                                    Boursault 

Family:                                                      Ericaceae 

Size:                                                         Height: 0 ft. to 5 ft. Width: 0 ft. to 0 ft. 

Plant Category:                                           shrubs, 

Plant Characteristics:                                    

Foliage Characteristics:                                 evergreen, 

Foliage Color:                                             green, 

Flower Characteristics:                                 long lasting, 

Flower Color:                                              purples, 

Tolerances:                                                drought, pollution, slope, 

Requirements

Bloomtime Range:                          Mid Spring to Late Spring 

USDA Hardiness Zone:                    4 to 8 

AHS Heat Zone:                             Not defined for this plant 

Light Range:                                 Part Shade to Sun 

pH Range:                                    5 to 6.5 

Soil Range:                                   Sandy Loam to Clay Loam 

Water Range:                                Dry to Normal 

Plant Care:

Fertilizing

How-tos : Fertilization for Established Plants  Established plants can benefit from fertilization. Take a visual inventory of your landscape. Trees need to be fertilized every few years. Shrubs and other plants in the landscape can be fertilized yearly. A soil test can determine existing nutrient levels in the soil. If one or more nutrients is low, a specific instead of an all-purpose fertilizer may be required. Fertilizers that are high in N, nitrogen, will promote green leafy growth. Excess nitrogen in the soil can cause excessive vegetative growth on plants at the expense of flower bud development. It is best to avoid fertilizing late in the growing season. Applications made at that time can force lush, vegetative growth that will not have a chance to harden off before the onset of cold weather. 

Light

Conditions : Partial Shade  Partial Shade is defined as filtered light found beneath trees with high limbs. Partial shade usually offers some protection from direct afternoon sun.  Conditions : Part Sun  Part Sun refers to filtered light, with most sun being received during the afternoon hours. Shade usually occurs during the morning hours.  Conditions : Partial Sun, Partial Shade  Part sun or part shade plants prefer light that is filtered. Sunlight, though not direct, is important to them. Often morning sun, because it is not as strong as afternoon sun, can be considered part sun or part shade. If you live in an area that does not get much intense sun, such as the Pacific Northwest, a full sun exposure may be fine. In other areas such as Florida, plant in a location where afternoon shade will be received.  Conditions : Full to Partial Sun  Full sunlight is needed for many plants to assume their full potential. Many of these plants will do fine with a little less sunlight, although they may not flower as heavily or their foliage as vibrant. Areas on the southern and western sides of buildings usually are the sunniest. The only exception is when houses or buildings are so close together, shadows are cast from neighboring properties. Full sun usually means 6 or more hours of direct unobstructed sunlight on a sunny day. Partial sun receives less than 6 hours of sun, but more than 3 hours. Plants able to take full sun in some climates may only be able to tolerate part sun in other climates. Know the culture of the plant before you buy and plant it!  Conditions : Types of Pruning  Types of pruning include: pinching, thinning, shearing and rejuvenating.

Pinching is removing the stem tips of a young plant to promote branching. Doing this avoids the need for more severe pruning later on. Thinning involves removing whole branches back to the trunk. This may be done to open up the interior of a plant to let more light in and to increase air circulation that can cut down on plant disease. The best way to begin thinning is to begin by removing dead or diseased wood. Shearing is leveling the surface of a shrub using hand or electric shears. This is done to maintain the desired shape of a hedge or topiary.

Rejuvenating is removal of old branches or the overall reduction of the size of a shrub to restore its original form and size. It is recommended that you do not remove more than one third of a plant at a time. Remember to remove branches from the inside of the plant as well as the outside. When rejuvenating plants with canes, such as nandina, cut back canes at various heights so that plant will have a more natural look. 

Watering

Conditions : Regular Moisture for Outdoor Plants  Water when normal rainfall does not provide the preferred 1 inch of moisture most plants prefer. Average water is needed during the growing season, but take care not to overwater. The first two years after a plant is installed, regular watering is important. The first year is critical. It is better to water once a week and water deeply, than to water frequently for a few minutes.  Conditions : Moist and Well Drained  Moist and well drained means exactly what it sounds like. Soil is moist without being soggy because the texture of the soil allows excess moisture to drain away. Most plants like about 1 inch of water per week. Amending your soil with compost will help improve texture and water holding or draining capacity. A 3 inch layer of mulch will help to maintain soil moisture and studies have shown that mulched plants grow faster than non-mulched plants.  Conditions : Outdoor Watering  Plants are almost completely made up of water so it is important to supply them with adequate water to maintain good plant health. Not enough water and roots will wither and the plant will wilt and die. Too much water applied too frequently deprives roots of oxygen leading to plant diseases such as root and stem rots. The type of plant, plant age, light level, soil type and container size all will impact when a plant needs to be watered. Follow these tips to ensure successful watering:

* The key to watering is water deeply and less frequently. When watering, water well, i.e. provide enough water to thoroughly saturate the root ball. With in-ground plants, this means thoroughly soaking the soil until water has penetrated to a depth of 6 to 7 inches (1' being better). With container grown plants, apply enough water to allow water to flow through the drainage holes. * Try to water plants early in the day or later in the afternoon to conserve water and cut down on plant stress. Do water early enough so that water has had a chance to dry from plant leaves prior to night fall. This is paramount if you have had fungus problems. * Don't wait to water until plants wilt. Although some plants will recover from this, all plants will die if they wilt too much (when they reach the permanent wilting point). * Consider water conservation methods such as drip irrigation, mulching, and xeriscaping. Drip systems which slowly drip moisture directly on the root system can be purchased at your local home.