- A few Rhododendron facts
- Planting rhododendron
- Pruning and caring for rhododendron
- Problems with growing rhododendron
- Diseases and parasites attacking rhododendron
- Learn more about Rhododendron
- Smart tip about rhododendrons
- Plant Database
- Rhododendron calendulaceum
- Rhododendron calendulaceum (Michx.) Torr.
- Synonym(s): Azalea calendulacea, Azalea lutea
- USDA Native Status: L48 (N)
- Rhododendron Flower (Meaning, Varieties & Facts)
- Facts About Rhododendron
- Varieties Of Rhododendron
- Uses Of Rhododendron
- Seed Ecology
- Dwarf Rhododendrons
- Azaleas and Rhododendrons – what’s the difference?
I have heard all kinds of ways and times to deadhead rhododendrons. Please settle this question once and for all. When is the best time and what is the correct procedure to deadhead rhododendrons? Thank you!
You’re right! There is a lot of information and opinions about rhododendrons out there. It is important to understand that there are oodles of varieties. The important thing is to try to find out what variety you have and then learn how it thrives best. In general, you should deadhead the flowers once the petals are wilting by snapping off or cutting the top stalk, which supports the petals. Go down to the first ring of leaves without taking any leaves off the branch. You can do this to each flower head while the shrub is still in bloom. This is deadheading. Now, pruning your rhody is a different concept.
Rhododendrons do not need to be pruned every year — only when you need to shape your plant or help promote growth because it is looking too leggy, with too much branch showing. Some varieties will do much better than others when drastically cut back. If you do prune the shrub, it will inhibit the next year’s blooms, but that is good for the plant in the long run. You can cut branches back while it is blooming and enjoy the flowers inside, or prune immediately after blooming. Also, if a rhododendron needs drastic pruning, you do not have to prune the entire plant in one year but could spread the pruning out over three years. When cutting it back, always cut the branch right above a whorl of leaves.
In mild climates rhododendrons and azaleas can be planted almost any time of the year with reasonable success. In colder areas, early spring planting is recommended, with early fall planting being a second choice. In hot areas, fall planting is recommended, as this allows the plant’s root system to get well established during the colder fall and winter months.
Rhododendrons and azaleas do well with direct light for at least part of the day. Excessive shade normally results in very limited flowering. In hot areas, northern exposures are preferable to southern exposures. Exposure to constant wind is not desirable, especially the salty winds of marine environs. Generally large-leaf rhododendrons are less tolerant of sun and wind than small-leaf rhododendrons or evergreen and deciduous azaleas.
Proper soil conditions are very important. (See Soil Conditions for more information.) Rhododendrons are acid loving plants. As such they perform best when the soil is acidic (with a pH between 4.5 and 6.0). They need well-draining soil with an abundance of organic matter. Rhododendron and azalea roots also need oxygen for healthy growth. Many materials can be used to amend the soil. Compost or decomposed pine bark are very effective. Heavy clay soils collect and retain water so it is recommended to plant rhododendrons and azaleas above the base clay soil in a mound of desirable soil. (See Figure below.) If you dig a hole in heavy soil and fill it back with a light soil mixture, you may be creating a bucket which will hold significant water.
The top of the root ball should never be below the level of the surrounding soil. The top of the root ball should be planted several inches above the surrounding soil. Planting rhododendrons and azaleas too deep can eventually lead to plant death.
Planting near concrete foundations or other concrete materials is to be avoided as the concrete creates alkaline conditions (a pH of 6 or above) that are harmful for healthy rhododendron and azalea growth. People often use aluminum sulfate to lower the pH of soil, i.e. make it more acidic, for growing hydrangeas. Using aluminum sulfate to acidify rhododendron soil is not recommended as aluminum is toxic to rhododendron and azalea roots. To lower soil pH use wettable sulfur or ferrous sulfate.
In hot climates, root rot organisms flourish in wet soils and can kill rhododendrons and azaleas. Under these conditions, raised planting beds that incorporate 50% or more fine pine bark can be helpful in suppressing Phytophthora root rot. Extreme cases may require the use of fungicides such as Subdue or Aliette. Always read and follow label instructions when using chemicals. Soil from plants that have succumbed to Phytophthora should not be reused to plant more rhododendrons.
Plants should be thoroughly watered prior to planting. The roots should be loosened. Root bound plants that have been in containers for a lengthy time should be thoroughly loosened, and some of the outer roots cut. With a knife make vertical cuts 2″ or more deep, equally spaced around the sides of the root ball. Use your hands to gently loosen the roots where cuts were made and pull the roots outward. This will stimulate new root growth and allows water and nutrients to penetrate into the root mass.
Field grown plants are dug up with a ball of soil around their roots, and the ball is then wrapped in burlap or a synthetic material and tied with twine or wire. Such balled-and-burlapped plants can be damaged if handled roughly. Always support the bottom of the root ball when moving the plant; avoid dropping the plant which might shatter the root ball. The burlap may be left on the root ball unless it is plastic or otherwise non-biodegradable. Open up the biodegradable burlap and lay it well back from the trunk, remove any cord or wire. Field grown plants typically are grown in heavy soil that holds the ball together when dug. Loosen the rootball and cut some of the roots to stimulate the growth of new roots. The texture of the soil surrounding the root ball should match that of the rootball.
Rhododendrons and azaleas rely upon their shallow root structure for their water and nutrients. It is very beneficial to mulch around the plant at least out to the drip line. Do not pile the mulch right up to the trucks, leave 5″ – 6″ free of mulch. Mulching helps accomplish several important functions. It helps in keeping the soil moist and cool. As it decomposes it provides nourishment for the plant. Competing plants and weeds have a more difficult time getting established so they are not taking the moisture and nutrients. Many materials are useful as mulch, such as fir bark, pine needles, wood chips, composted materials, etc. Ideally, the mulch should have loose texture to allow water and air to reach the root zone. Chips, bark, compost materials, etc. should be allowed to age at least for a season so that they do not use up the available nitrogen to decompose, thus leaving less for the rhododendrons. They are not sufficiently decomposed if they heat up.
Index of Contents
Pruning & Spent
Insect & Disease Control
Rhododendrons are among the most beautiful heath soil shrubs.
A few Rhododendron facts
Name – Rhododendron
Family – Ericaceae
Type – shrub
Height – 1 ⅓ to 16 feet (0.5 to 5 meters)
Exposure – part sun and shade
Soil – acid, heath soil
Foliage – evergreen
Flowering – April-May
Planting, pruning and caring for them are steps that help enhance blooming and avoid diseases.
One of the most important considerations when planting rhododendron is the need to have heath and well drained soil.
If your soil is chalky or limestone soil, it is recommended to dig a much larger hole and fill it in with heath.
Rhododendron tolerates shade, part sun and even sunlit places, as long as it stays cool.
- We recommend planting rhododendron in fall.
Planting is tolerated in spring or winter, as long as it doesn’t freeze.
If you wish to plant in summer, provide for regular watering at the beginning.
- Choose a partially shaded or sunlit spot that never gets scorching hot.
- Avoid flood-prone areas at all costs, because this shrub hates sitting water.
- Follow our advice on planting heath plants and shrubs.
- Read also: Growing and caring for potted rhododendron
Making cuttings is the easiest and fastest technique to propagate rhododendron.
Preparing rhododendron cuttings can be done all summer long.
- Collect 6 to 8 inch (15 to 20 cm) cuttings from non-flowering stems.
- Remove lower pairs of leaves, keeping only the topmost one or two pairs.
- If you so wish, dip the base of the cuttings in powdered rooting agents.
- Place your cuttings in nursery pots filled with cutting soil mix.
- Keep the substrate moist and put the cuttings near light, but not in direct sunlight.
Pruning and caring for rhododendron
It isn’t really necessary to prune rhododendron, so caring for them is easy.
Pruning is only needed if you wish to maintain the figure, reduce the size of the shrub, or balance growth:
- Remove dead wood.
- Remove wilted flowers regularly (deadheading).
- To reduce shrub size, wait for the end of the summer and cut just above a bud so it will split into multiple branches.
It is important for the soil to remain slightly moist at all times, and for that the best solution is to mulch with pine bark mulch.
Problems with growing rhododendron
Rhododendron leaves and buds turn brown
This is often due to poorly-draining soil, which means water is stagnating around the roots.
- Rhododendron must never have stagnant water around its roots, water must flow away quickly.
- It makes sense in this case to mix some sand into the soil. It especially helps to spread a layer of clay marbles or pebbles at the bottom of the hole to help water seep into the ground.
Rhododendron is actually more hardy than they are able to overcome excess water in the ground…
Finally, fertilizing with special heath plant fertilizer at the end of winter strengthens rhododendron, enhances their flowering and helps avoid diseases.
Leaves lose their color and turn yellow
This is generally due to excessively chalky soil, and results in what is called rhododendron chlorosis.
- Adding a layer of heath the soil in the surface is recommended.
- A supplement of heath plant fertilizer should also help cure the chlorosis.
Diseases and parasites attacking rhododendron
Rhododendrons are shrubs that resist diseases well when they are well settled in, roots have developed well, and growing conditions are favorable.
Inversely, if there is either excess water or excess heat, or it hasn’t been planted correctly, it is more vulnerable to various diseases, listed below:
Rhododendron withers, looks sad and stunted
This is one of Rhododendron’s most common diseases, and it is often too late when it shows.
- It is usually due to a fungus that is called Phytophthora cinnamomi. This fungus often is lethal to rhododendrons.
- Treatment must be swift and merciless, removing and destroying the infested portions of the shrub, but survival chances are slim.
- Once all infested portions have been removed, treat with systemic fungicide, which is the only effective option against this fungus.
Blisters form on leaves
- Even though this is not often critical, this fungus-based disease is due to Exobasidium vaccinii, and is more commonly called leaf gall.
- Usually, it is enough to remove the leaves that host these blisters.
Learn more about Rhododendron
Rhododendrons boast amazing flowers at the very beginning of spring, and their leaves are gorgeous all year round.
This plant can grow to live very old and can even reach majestic sizes, some shrubs reaching heights of over 16 feet (5 meters).
Rhododendron flowers are grouped in bouquets that can span 8 to 10 inches (20 to 25 cm) across, with hues shifting in ranges of pink to red, including white and violet depending on the species.
Rhododendrons are particularly decorative, and are among those shrubs that are best suited to shaded areas.
Smart tip about rhododendrons
Since it is quite acidic, pine bark mulch is definitely the best mulching option.
Mulch the base of the tree in summer to keep a good level of moisture.
- Read also: Growing and caring for potted rhododendrons.
Rhododendron calendulaceum (Michx.) Torr.
Synonym(s): Azalea calendulacea, Azalea lutea
USDA Native Status: L48 (N)
Flame azalea is an upright-branched deciduous shrub, 6-12 ft. tall and equally as wide, with large, showy, funnel-shaped flowers in clusters of 5 or more. Summer foliage is medium green and the fall color is subdued yellow to red. The non-fragrant flowers, appearing before or with the leaves, vary in color from pale yellow to apricot to brilliant scarlet red. A deciduous shrub with terminal clusters of tubular, vase-shaped, orange, red, or yellow flowers.
This beautiful southern Azalea forms striking displays on some of the grassy balds of the southern Appalachians. A wide variation of color forms occurs, from all shades of yellow to orange-yellow and scarlet. The flowers appear before or with the new leaves. This species is extensively planted as an ornamental. Like most members of the heath family, it does best in acid soil.
From the Image Gallery
Autumn Foliage: yes
Size Class: 6-12 ft.
Bloom Color: Red , Orange , Yellow
Bloom Time: May , Jun
USA: AL , CT , GA , KY , MD , NC , NY , OH , PA , SC , TN , VA , WV
Native Distribution: NY to s. OH, s. to GA & MS
Native Habitat: Dry, rocky, mountain woods; heath balds
Light Requirement: Part Shade
Soil Moisture: Moist
Soil pH: Acidic (pHSoil Description: Well-drained soil.
Conditions Comments: Rhododendron calendulaceum tolerates dry soil. It needs at least a few hours of sun each day, proper soil, and careful pruning when young for the best floral displays. Floral show lasts nearly two weeks. Good cultural practices reduce the incidence of disease and insect damage.
Warning: Rhododendrons contain poisonous substances and should not be ingested by humans or animals. Honey made from flowers also may be toxic. POISONOUS PARTS: All parts. Highly Toxic, May be Fatal if eaten. Symptoms include salivation, watering of eyes and nose, abdominal pain, loss of energy, depression, nausea and vomiting, diarrhea, weakness, difficult breathing, progressive paralysis of arms and legs, coma. Toxic Principle: Andromedotoxin. (Poisonous Plants of N.C.)
Value to Beneficial Insects
Special Value to Bumble Bees
This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.
Description: Combine seeds loosely with sphagnum moss and sprinkle lightly over a 2:1 perlite/peat mixture. Germinate under mist or a plastic tent. Optimum temperatures for germination are 45-50 degrees. Transplant seedlings to acid soil with a high content of orga
Seed Treatment: No pretreatment is necessary.
Commercially Avail: yes
From the National Organizations Directory
According to the species list provided by Affiliate Organizations, this plant is on display at the following locations:
Delaware Nature Society – Hockessin, DE
Mt. Cuba Center – Hockessin, DE
Bibref 1620 – Gardening with Native Plants of the South (Reprint Edition) (2009) Wasowski, S. with A. Wasowski
Search More Titles in Bibliography
USDA: Find Rhododendron calendulaceum in USDA Plants
FNA: Find Rhododendron calendulaceum in the Flora of North America (if available)
Google: Search Google for Rhododendron calendulaceum
Record Modified: 2015-05-28
Research By: TWC Staff
Rhododendron ponticum is a successful invasive species, especially in the British Isles. Due to its adaptations, it can typically outcompete any native plants trying grow in the same area. This invasion leaves land damaged. Due to the high cost and difficulty involved in restoring the land, it is often abandoned.
Attempts to control this invasion are either too expensive, dangerous to other organisms living in the area, or physically demanding. However, alternate methods to control the invasion are being looked into. For example, if the seed dispersal patterns can be accurately predicted, one may be
able to stop the plant before it spreads. © Copyright The Reader’s Digest
Also, if researchers can determine how to Association, Inc. 1987
prevent insects from pollinating the flowers,
the spread of Rhododendron ponticum
could also be slowed down.
Rhododendron was discovered in the 16th century by Charles l’Ecluse, a Flemish botanist.
There are more than 6,000 different cultivated varieties of Rhododendron.
Did you know that since Rhododendrons require acidic soil, they are sometimes called acid loving plants?
A well-established Rhododendron ponticum requires an herbicide with unique chemicals and several treatments over many years in order to kill it and keep it from returning.
Rhododendron Flower (Meaning, Varieties & Facts)
Rhododendron is a genus of 1,024 species of woody plants in the heath family (Ericaceae).
Updated: August 25, 2019
Rhododendron is a genus of 1,024 species of woody plants in the heath family (Ericaceae), either evergreen or deciduous. These are found mainly in Asia, although it is also widespread throughout the highlands of the Appalachian Mountains of North America. Most species have brightly colored flowers which bloom from late winter through to early summer. The name Rhododendron comes from the greek words “rodon” which means “rose” and “dendron” which means “tree”, hence Rose Tree. Rhododendrons are referred to as the King of Shrubs since they are regarded by many as the best flowering evergreen plants for the temperate landscape.
Facts About Rhododendron
- Rhododendron is the national flower of Nepal as well as the state flower of West Virginia and Washington in United States.
- It is the state tree of Sikkim and Uttarakhand in India.
- Rhododendrons is known as as big leathery leafed shrubs with round clusters of white, pink, red, or purple blooms.
- The smallest species grows to 10-100 cm (4-40 in) tall, and the largest, R. protistum var. giganteum, up to 30 m (100 ft) tall.
- The leaves are spirally arranged. Leaf size can range from 1-2 cm (0.4-0.8 in) to over 50 cm (20 in), exceptionally 100 cm (40 in) in R. sinogrande.
- They may be either evergreen or deciduous. In some species, the undersides of the leaves are covered with scales (lepidote) or hairs (indumentum).
- Some of the best known species are noted for their many clusters of large flowers.
- There are alpine species with small flowers and small leaves, and tropical species such as section Vireya that often grow as epiphytes. Species in this genus may be part of the heath complex in oak-heath forests in eastern North America.
- Rhododendron are characterised by having inflorescences with scarious (dry) perulae.
- It has fruit that has a septicidal capsule, an ovary that is superior (or nearly so), stamens that have no appendages, and agglutinate (clumped) pollen.
- Rhododendron was discovered by The 16th century Flemish botanist, Charles l’Ecluse.
- Rhododendron was introduced to Britain in 1656 from the European Alps, and so the name Alpine Rose for Rhododendron histrum.
- Rhododendron symbolizes danger and to beware.
- Pink Rhododendron (Rhododendron campanulatum) is the State Flower of Himachal Pradesh, India.
- Rhododendron is also the state flower of Nagaland.
- Rhododendron maximum, the most widespread rhododendron of the Appalachian Mountains, is the state flower of the US state of West Virginia, and is in the Flag of West Virginia.
- Rhododendron macrophyllum, a widespread rhododendron of the Pacific Northwest, is the state flower of the US state of Washington.
Varieties Of Rhododendron
Rhododendrons may be divided into the following groups:
Large group of evergreen shrubs that vary greatly in size. Most rhododendron flowers are bell-shaped and have 10 stamens.
Vireya (Malesian) rhododendrons:
Epiphytic tender shrubs
Group of shrubs which have smaller and thinner leaves than evergreen rhododendrons. They are generally medium-sized shrubs with smaller funnel-shaped flowers that usually have 5 stamens:
Deciduous hybrid azaleas:
Exbury hybrids: derived from the Knap Hill hybrids, developed by Lionel de Rothschild at the Exbury Estate in England.
Ghent (Gandavense) hybrids: Belgian raised Knap Hill hybrids: developed by Anthony Waterer at the Knap Hill Nursery in England.
Mollis hybrids: Dutch and Belgian raised
New Zealand Ilam hybrids: derived from Knap Hill/Exbury hybrids
Occidentale hybrids: English raised
Rustica Flore Pleno hybrids: sweet-scented, double-flowered
Evergreen hybrid azaleas:
Gable hybrids: raised by Joseph B. Gable in Pennsylvania.
Glenn Dale hybrids: US raised complex hybrids
Indian (Indica) hybrids: mostly of Belgian origin
Kaempferi hybrids: Dutch raised
Kurume hybrids: Japanese raised
Kyushu hybrids: very hardy Japanese azaleas
Oldhamii hybrids: dwarf hybrids raised at Exbury, England
Satsuki hybrids: Japanese raised, originally for bonsai
Shammarello hybrids: raised in northern Ohio
Vuyk (Vuykiana) hybrids: raised in the Netherlands
semi-evergreen hybrids between deciduous azaleas and rhododendrons
Uses Of Rhododendron
- In the Indian state of Himachal Pradesh, rhododendron flowers have been used for some time to make popular fruit and flower wines.
- In Nepal, the flower is considered edible and enjoyed for its sour taste. The pickled flower can last for months and the flower juice is also marketed.
- The flower, fresh or dried, is added to fish curry in the belief that it will soften the bones.
- The juice of rhododendron flower is used to make a squash called burans (named after the flower) in the hilly regions of Uttarakhand. It is admired for its distinctive flavor and color.
- The herbal tea called Labrador tea (not a true tea) is made from one of three closely related species: Rhododendron tomentosum, Rhododendron groenlandicum and Rhododendron neoglandulosum
- Rhododendron species have long been used in traditional medicine.
- Animal studies and in vitro research has identified possible anti-inflammatory and hepatoprotective activities which may be due to the antioxidant effects of flavonoids or other phenolic compounds and saponins the plant contains.
All the parts of Rhododendrons are dangerous, especially leaves, showing symptoms of Stomach irritation, abdominal pain, abnormal heart rate and rhythm, convulsions, coma, death. Honey made from the nectar of Rhododendron flowers is also toxic and should not be consumed.
How to Grow Rhododendrons from Seed
Allan and Shirley Anderson
Franklin Lakes, New Jersey
Growing rhododendrons and azaleas from seed is not difficult if one remains conscious of their physical needs, e.g., light, warmth, fertilizer and moisture. As long as these are provided at the proper time and in the right amount, many methods have been successful. Rhododendron seedlings are adaptable and can succeed with less than ideal environmental factors, but it is important to remember that whatever method issued the planting medium must never be allowed to dry out. Germinating seeds or small seedlings cannot survive even one such episode.
We grow our seeds on damp, slightly firmed milled sphagnum moss in small plastic “deli” containers. Screened peat moss and perlite mixtures have been equally successful. We drop the seeds on the surface and enclose the container in a polyethylene sandwich bag with the top folded under the container. Such an enclosure will usually keep the medium moist until the seeds germinate at which time the bags are gradually opened and medium watered carefully to be sure it doesn’t dry out. Each container is labeled and contains seed of a single variety.
While seeds do not require light to germinate they do need light to photosynthesize and grow immediately after. We therefore put the containers on a bed of peat moss over the heating cable and suspend a light source over the top. A fluorescent shop light about 8 inches over the containers works well. A time switch is used to provide about 16 hours of light each day. In the past years we handled fewer containers by placing them on a serving tray on top of the refrigerator for warmth. A desk lamp with a time switch provided light. We have also used old aquariums using an automatic heating cable in the bottom with a layer of damp peat moss under the deli containers.
While some seeds, especially yakushimanum hybrids, may germinate unpredictably, most other hybrids and species seed germinates in 10 days to 3 weeks time. In 4 to 8 weeks more the small seedlings will have two or four true leaves in addition to the original cotyledons. Now we transplant them into flats containing a screened peat-perlite mixture and fertilize every other watering with one-third strength soluble acid type fertilizer (Miracid® or equivalent). About 50 seedlings are planted in each flat. We still maintain the 16-hour days with overhead light.
We place the flats on the bench in a small greenhouse, but other hybridizers have used basement tables under suspended fluorescent lights, sun porches or various types of light stands. Just remember the basic requirements which are moisture, weak fertilizer, light for 16 hours a day and warmth, about 70°F if you can provide it.
When weather permits and natural days become longer the flats are placed outdoors in a moderately shaded area. Supply with one-half strength soluble fertilizer and water as needed to prevent drying. The seedlings will grow through the summer. We stop fertilizing about the middle of July, and in the fall we transfer the 3 to 6-inch plants into individual containers for winter protection under plastic. In earlier years we left the seedlings in the original flats and wintered them over in cold frames for planting out in the spring.
At this point seedlings are much like other small plants such as mericlones* or rooted cuttings. They will still need some protection outdoors from wind and too much sun. Windbreaks and partial shade from high trees or snow fencing, etc., are described in many books.
Whether you want to try a few or many, the growing of rhododendron seeds is great fun and an absorbing pastime. We recommend it!
* At this stage of growth the seedlings may be handled as if they were rooted cuttings or like the mericlone propagules sometimes sold at plant sales and supplied by tissue culture labs.
The Problem of Growing Rhododendrons from Seed
by M.J. Harvey – February 2002
The seed ecology of rhododendrons is that they produce very large numbers of very small seeds. Why is this? The answer is that they occupy a particular niche in the forest.
Take the horsechestnut. It has a huge seed that weighs around 12 gm. dryweight. This mass represents a lot of starch to provide energy for the growing seedling. By the way, the starch is protected from being eaten by animals by a generous admixture of the intensely bitter saponin aeschlin. This large seed, given a suitable site can quickly produce a deep root and a strong shoot without the need for much initial photosynthesis. The starch represents maternal care. (Who said plants didn’t have maternal care?) These seedlings can then, given a chance, become forest giants. They are one of the emergent, canopy species.
Contrast your rhododendron seed. No, I have not weighed one. Say a single seed weighs 1 mg. for the sake of comparison. Not much maternal investment there – “You’re on your own son.” But by the way of compensation there are huge numbers of seeds that get blown hither and thither in the wind. Why? Well the rhododendron is exploiting the understory niche. The seeds are being sent out to find a gap in the vegetation – some damp patch of substrate where another plant recently died or toppled over. In these very precise habitats rhododendron seeds can germinate, put out their tiny leaves and start to photosynthesise. Their motto is ‘photosynthesise or die’. If the site is too dark they can’t capture light energy, and die. If the site is too exposed, windy or sunny, they also die because without the 12 gm. of starch they can’t get a root deep down in a hurry.
I called rhododendrons ‘Understory Shrubs’. Anyone seeing Peter Wharton’s January slide show from the NW Yunnan border would have been impressed by the 60 foot specimens, growing in some cases horizontally from a cliff.
So folks, please try growing rhododendrons from seed and don’t be disappointed if they die. You might say they are pre-programmed to die unless they find themselves in a very narrow band of conditions.
The stunning flowers of the Rhododendron have earned them a legion of fans, and quite right too! Some varieties of full size Rhododendrons will simply keep growing until they grow into giant trees, although you can prune them down, these larger varieties may not be an option in your garden.
This month we’re taking a look at some stunning dwarf varieties. The compact growth habit of these shrubs give them an outstanding formal appearance, making them ideal for small city gardens or courtyards where space is at a premium. They’re even small enough to slot nicely beneath taller shrubs in the border, or grow nicely in a rock garden.
Rhododendron Princess Anne
A dwarf evergreen shrub variety with soft primrose yellow flowers which appear in spring, sitting nicely alongside the green foliage. A very reliable performer, its holds the RHS Award of Garden Merit. Height and spread only 50-60cm as adult plant.
Rhododendron Dwarf Collection
Our collection brings together Scarlet Wonder (red), Moerheim Lilac (lilac/mauve) and Pink Drift (cool-toned, light pink). A burst of colour for your border or patio, all three are exceptionally compact and manageable. These varieties produce trusses of up to three funnel shaped, vibrant flowers from April-June, against a lush background of ovate, glossy dark green leaves.
You can plant out in March/April or in October.
Prepare the ground by digging in plenty of compost, neutral or acidic organic matter, or leafmold etc. Plant so the roots are covered, not too deep and apply a good layer of mulch lightly over the surface, don’t pack it down. Re-mulch and feed with an ericaceous fertiliser each spring.
Ericaceous fertiliser? This is for plants that are not as happy in limey soils. It’s a lime-free acidic compost that was habitually made with peat – however as awareness that adding peat to soils is bad for the environment you can now easily find peat free varieties to buy.
Dwarf varieties can cope with positioning in full sun but need evenly moist, well drained soils so keep on top of watering them in the hottest part of summer. Rhododendrons like lots of water and use rain-water if you can – you should particularly avoid tap-water if you live in a hard water area. As with larger Rhododendrons they won’t do at all well subjected to frost so take care to protect them and avoid areas you know are prone to it in your garden.
Technically this one will reach a mature height of 150cm, so not quite as dwarf as the varieties above but this stunning variety shouldn’t be missed out. Its one of the earliest flowering varieties, producing an abundance of rose-purple blooms as early as February and throughout March. It holds the Royal Horticultural Society’s Award of Garden Merit.
Azaleas and Rhododendrons – what’s the difference?
In truth not very much! Azaleas are a group within the Rhododendron family and they have some small differences. Rhododendrons will have ten or more stamens, while an Azalea will usually have five stamens. Rhododendrons have larger leaves and they will be paddle-shaped, Azalea have smaller, elliptical leaves. Also Rhododendrons are evergreen, whereas Azaleas can be evergreen or deciduous.