Rhododendrons are some of the most vibrant plants you can add to the garden. Reliable and long lasting, many rhododendron varieties provide year round color and structure to a space.
As well as highlighting some of the most attractive rhododendron varieties currently available, this article will also seek to explain exactly what these colorful, showy plants are. Finally, we will also provide some general care and planting tips, allowing you to help your chosen plant, or plants, thrive in your garden.
These versatile shrubs are both colorful and low maintenance.
What are Rhododendrons?
The plant’s name is derived from the Greek words Rodon, meaning rose, and Dendron, which means tree. The name perfectly describes the tall growth habit of these hardy bushes. During the spring and summer colorful, bell shaped flowers form in clusters all over the plant.
Many rhododendron varieties are found wild in Asia. The plants can also be found growing wild in the Appalachian mountains. First discovered in the 16th century, these attractive flowering shrubs have been cultivated for centuries.
Is my Plant an Azalea or a Rhododendron?
Often confused, these two plants are not actually two separate species. All azaleas are rhododendrons. However, not all rhododendron varieties are azaleas.
Azaleas are smaller in both height and width. The flowers of both plants are similar. One distinguishing feature, which is easy to spot, is that the azalea flower typically has 5 stamens while rhododendrons have 10. Finally, azaleas are deciduous, most rhododendron varieties are evergreen.
There are over 1000 recorded rhododendron varieties but less than 20 of these are commonly grown.
In some areas, such as the UK, the plants are so prolific that they are considered invasive. Most invasive varieties are not true plants but a hybrid cultivar, rhododendron ponticum. To prevent the spread, cultivation of this particular breed has ceased. Instead nurseries are developing noninvasive, ornamental cultivars.
Ornamental rhododendron varieties come in 3 types. None of these are considered invasive. The 3 ornamental varieties are:
- Evergreen shrubs, smaller than trees, can flower throughout the year. Evergreens are a good choice for year round greenery.
- Deciduous shrubs, these are small plants that drop leaves in the fall and in winter.
- Evergreen trees, trees that stay green throughout the year.
Now that we have established what they are, here are some of the most popular rhododendron varieties.
Elvira is one of the many evergreen rhododendron varieties. A broadleaf shrub, in the spring cherry red trumpet-shaped flowers develop at the end of the branches. The blooms are lightly scented, further adding to the attraction. Elviira’s dark, coarse foliage has a compact, mounded growth habit.
Elviira is best planted in richly organic, well draining soil that is slightly acidic. In soil that is not well draining Elviira, like other rhododendron varieties, struggles to survive. Typically reaching 24 inches tall and wide, these are slow growing plants that in ideal conditions can survive up to 40 years.
In favorable conditions, Elviira is a low maintenance plant. A popular specimen plant, Elviira can also be planted in containers or used to edge the borders of flower beds.
Red flowering varieties are amongst the most popular.
2 Blue Peter
Blue Peter is evergreen or deciduous depending on the planting zone. Best planted in well draining, humus rich soil, like other rhododendron varieties Blue Peter prefers an acidic soil.
Pleasingly cold hardy, Blue Peter is also sun and heat tolerant meaning that it can cope in a more open position. A great hedging or screening option thanks to its erect growth habit, Blue Peter’s large, green foliage is both colorful and dense. The flowers, which are tubular and violet-blue in color, emerge in attractive clusters. Further adding to the interest are the frilled petals.
Blue Peter is a bushy shrub that can reach up to 9 ft in ideal conditions. The plants can be used in a range of planting schemes including cottage gardens.
Specks and streaks of color further the interest of these colorful blooms.
3 Boule de Neige
Boule de Neige is another of our evergreen rhododendron varieties. A round shrub with dense broadleaves, Boule de Neige has an upright, wide growth habit. If allowed to, the plant can reach up to 10 ft tall and 3 ft wide. Luckily a slow growth habit means that despite being capable of spreading out over a wide area, you won’t have to prune it too frequently.
Best planted in loamy or acidic soil, the flower buds of Boule de Neige are an attractive shade of pink. These open to reveal funnel-shaped white flowers, the petals of which can be decorated with yellow or brown flecks. Further adding to the attraction, the elliptical foliage of Boule de Neige is a pleasing light green shade. Ideal for a range of gardens, regularly pruning the plants means that they are also suitable for containers, patios and small spaces.
Pale white blooms help to create a soothing space, ideal for planting around a patio.
4 Bow Bells
Another evergreen shrub with a vertical growth habit, Bow Bells is a slow growing plant. Over the course of 10 years Bow Bells will grow about 3 ft. Best planted in acidic, humus rich soil and in partial shade the Bow Bells produces masses of oval shaped leaves that are mid green in color. The underneath of the leaf is covered with dense, colorful hair.
The flowers of Bow Bells form in loose clusters. These are bell-shaped and pale pink, opening from bright pink buds. An ideal cottage garden choice, Bow Bells can also be used to screen an area or as hedging.
Hot pink flowers bring warmth and life to a flower bed.
Windsong is an evergreen cultivar which is popular for its slow and open growth habit. Rarely exceeding 4 ft in height, even after 10 years of steady growth, this is a particularly attractive, low maintenance choice.
Hardy down to 0 ℉ Windsong, like many varieties, does best in well draining, acidic soil. The flat glossy foliage is olive green in color. This provides an elegant backdrop to the frilly, funnel shaped yellow–green blooms. The showy flowers have dark red throats, further adding to the attraction. Windsong blooms develop on a bell shaped truss. This can hold up to 17 blooms, making Windsong an standout addition to the garden.
Pale yellow flowers help plants to stand out in even the most colorful planting scheme.
6 White Angel
Another evergreen variety with an upright growth habit, White Angel develops from a compact, round or vase shaped crown. One of the smaller rhododendron varieties, White Angel can reach a mature height of between 3 and 6 ft depending on the growing conditions.
White Angel plants are covered with leathery foliage which turns from light to dark green before developing a purple hue in the fall. A low maintenance plant that does best in an acidic soil that has been amended prior to planting, White Angel flowers emerge in either white or purple shades. These open from eye-catching pink buds. White Angel is one of the best lasting and showy rhododendron varieties currently available.
White flowers contrast nicely with deep green foliage.
7 Nova Zembla
Nova Zembla is an evergreen shrub popular for its rich red flowers which sit amongst thick, dark green leaves. The flowers form in large trusses, further adding to the attraction. Ideal for borders and foundation planting, Nova Zembla is also a good choice for a flowering hedge or privacy screen.
Nova Zembla has an upright growth habit, reaching 6 to 8 ft tall when fully mature. The plants also have a spread of between 5 and 7 ft. Best planted in well draining, moist, humus rich acidic soil Nova Zembla is one of the easiest rhododendron varieties to cultivate.
Varieties with large flowers and thick foliage can be planted to increase privacy in the garden.
8 Black Satin
A semi erect shrub, Black Satin is another of the many evergreen rhododendron varieties on our list. Reaching 3 to 6 ft tall, Black Satin varieties are popular for their showy flowers which emerge in abundance all over the plant during the late spring and summer months.
Best planted in well draining, evenly moist soil, Black Satin prefers conditions to be slightly acidic. When in flower, the rose pink blooms sit above small,dense foliage. Ideal for a forest planting scheme Black Satin can also be used in a winter garden. During the winter months, Black Satin’s foliage turns a shiny coal-black shade, adding interest to otherwise bare gardens.
In acidic soil, flowering is profuse.
9 Golden Oriole
The next entry in our list of rhododendron varieties, Golden Oriole is a hybrid azalea cross. Developed during the 19th century these attractive plants can reach up to 6 ft in height and spread just as widely.
Golden orange-yellow flowers emerge in the spring, sitting above attractive green foliage. During the fall, after the flowers have faded, the foliage maintains interest by turning an attractive shade of bronze. The dense foliage makes Golden Oriole a great hedging or screening plant.
Hybrid varieties are popular for their large blooms.
10 P.J.M. Elite
One of the hardiest rhododendron varieties, P.J.M. Elite is popular throughout North America for its vigorous growth habit and showy flowers. One of the most resilient rhododendron varieties, P.J.M. Elite can withstand heat and direct sunlight as well as it can freezing temperatures. This resilience has helped to bolster the popularity of P.J.M. Elite.
The trumpet shaped flowers, which emerge in large clusters, can be either white or pink-purple in color. Meanwhile the elliptical, glossy green foliage turns dark purple in the spring, prolonging the interest. Reliably producing masses of dense foliage and rarely exceeding 5 ft P.J.M. Elite is an ideal choice for rock gardens or flower beds.
When in flower the foliage can be hard to see.
A hybrid, the product of crossing the ornamental plant with Gable Stewartsonian, these evergreen specimens belong to the Gable hybrid group. A medium sized shrub with a low growth habit, Stewartsonian rarely exceeds 5 ft in either height or spread.
One of the showiest varieties on our list, Stewartsonian’s green foliage can be hard to see when the plant is in flower. During April and May, Stweartsonian’s vibrant, orange-red flowers practically cover the entire plant. Once the flowers fade the interest continues. During the fall and winter months, Stewartsonian’s foliage turns a shade of mahogany, providing year round interest.
Many varieties are popular for their long lasting, showy blooms.
A hardy azalea shrub with rich, evergreen foliage, Bloom-a-Thon flowers twice a year. Once in early April and again in early July. On both occasions the plant is covered with vibrant pink flowers. Pleasingly resistant to warm summer temperatures, Bloom-a-Thon often continues to flower until the first deep frosts of the year.
Reaching a mature height and spread of around 4 ft, Bloom-a-Thon is popular for its reliable, mounded growth habit. This showy plant is ideal for mass plantings, container gardens or for use as a specimen plant.
Vibrant, colorful blooms help to brighten gardens.
Care and Planting
Whatever rhododendron varieties you select, planting and general care is pleasingly easy. Most cultivars are evergreen and, when healthy, reasonably hardy.
If you have pets, particularly cats or dogs, you may want to avoid planting these specimens in your garden. These attractive shrubs are toxic to pets.
How to Plant
These attractive specimens have a reputation for being a little fussy. However, if you take the time to find the right planting location, they will thrive for many years with just minimal care.
Rhododendron varieties with large leaves like partial or dappled shade. A place which enjoys early afternoon shade is ideal. The edge of a tree canopy is an ideal position. Be careful not to select a position that is too shady. Azalea and dwarf varieties prefer full sun positions. If your garden is open with little to no natural shade, a Sunblock Shade Cloth is an easy way to shelter delicate plants.
These flowering shrubs are a popular choice for lining walkways.
The soil should be acidic and humus-rich. It should also be well draining. If the soil is too alkaline try to increase the acidity levels before planting. You will need to continually amend the soil after planting to ensure that acidity levels remain high. A more low maintenance solution is to plant in a container. If you don’t know the acidity levels of your soil, a soil test kit is a cheap and easy way to find out.
All rhododendron varieties dislike having wet feet. Soggy or waterlogged soil often causes these plants to fail. Amend heavy or clay soils before planting.
Avoid planting too close to large shrubs or trees which will steal the moisture and nutrients from the soil, depriving your growing plants. Finally, plant in a protected area away from strong or cold winds and frost pockets. The plants tolerate open positions if it isn’t very windy.
Unlike other large specimen shrubs and small trees, the roots of these plants rarely reach further than 12 inches deep. This means that they are unlikely to disturb or damage any underground infrastructure such as water pipes. However, the shallow roots also mean that all these otherwise resilient shrubs require more regular watering than other flowering shrubs. Mulching can help the soil to retain moisture without becoming waterlogged.
Finally, avoid planting near members of the walnut family, including pecans, hickories and butternuts. Walnut plants are toxic to all rhododendron varieties.
When to Plant
Most cultivars are best planted either in October or in the spring, during late March and April. If you are growing in containers, you can plant at any time of year. Planting in the fall is preferred. This gives the plants time to settle and establish roots before winter begins.
Plant when the soil is workable and not overly waterlogged. If you are planting in the spring, wait until the last chance of frost has passed.
Before planting, weed the soil and work in lots of ericaceous compost, this is lime free, or organic matter high in acidity. Pine needles, leafmould and composted tree bark are all ideal choices. Gathering fallen leaves and needles and placing them in a compost tumbler is a great way to create your own compost while also keeping your garden tidy. Avoid using animal manure on these plants. This often proves to be too strong for the sensitive, shallow roots.
When you are ready to plant, dig a hole as deep as the root ball and twice as wide. The aim is to plant the shrub at the same level as it was in the pot. The roots should sit just below soil level.
Remove the plant from its container and gently tease apart the roots. Position the plant in the center of the hole and half fill, being careful not to sink the plant as you do this.
Fill the hole with water from a garden hose and allow it to drain away. Once the excess moisture has drained away, continue to fill the hole. Apply a layer of mulch, 2 to 4 inches thick, around the plant. A bark chip or pine needle mulch is ideal. This provides a nutritious, acidic boost whilst also protecting the roots.
If you are planting more than one plant, space them 6 ft apart. You may be able to plant smaller varieties closer together. Check the plant information label before planting.
Regularly weed the soil during the growing season. This is best done by hand. A hoe may damage the plant’s shallow roots.
Most rhododendron varieties are native to areas with high rainfall. This means that they like the soil to be damp. In general, if it has rained less than 1 inch in the week, water your plants until the soil is wet to the touch. If you struggle to know when to water your plants, a soil moisture sensor is a useful way to measure the water content of the soil.
Shade loving annuals such as impatiens can be planted in front of established shrubs. This helps you to gauge when to water, if the plants are wilting then water the area. Low growing plants, such as impatiens, also provide good ground cover in shady areas, helping to suppress weed growth.
Growers in areas with hard water should harvest rainwater to use on their acid loving plants. Hard water contains calcium, which can reduce the acidity levels of the soil. As the soil is neutralized your plants start to suffer.
In poor soil an occasional dose of fertilizer encourages buds to set.
Fertilize the plants sparingly. Too much fertilizer may burn the roots. A slow release plant food, either a general purpose fertilizer or one designed for ericaceous plants, should be sprinkled around the base of the plants in early spring, as the flower buds start to fill out. Dr Earth Acid Lovers Organic Fertilizer is made specifically for acid loving plants. Simply sprinkle onto the soil and water in. Consult the instructions on the packet to work out how much fertilizer you need to apply. Avoid applying bone meal to your shrubs. This contains calcium which, as already noted, can lower the acidity level of the soil.
Most rhododendron varieties do not require much pruning. Once flowering has finished, remove any damaged or diseased branches. You may need to prune the plants every few years to reduce their height and spread. After a severe pruning the plants may not flower again for a few years. Selecting a plant that is an appropriate size for the planting area means that it is unlikely to require a severe pruning.
Deadhead spent blooms. This keeps the plants neat and healthy. It also prevents seeds from forming and spreading around the garden. Be careful when deadheading, next year’s buds form below the spent flower head.
Most rhododendron varieties are hardy in USDA Zones 4 to 8. In cooler areas, you may need to cover the plants with a REMIAWAY Shrub Jacket. This insulates the plants, protecting them from the potentially harmful effects of prolonged exposure to cold weather.
Rhododendron varieties are some of the most showy plants you can add to a garden. A great size to plug gaps in beds or hedges, the colorful foliage and flowers are a reliable way to introduce long lasting, low maintenance interest to your garden.