Loved for their bright and colorful flowers, Rhododendrons are making a major comeback in terms of being one of the most commonly sought after plants for contemporary gardens.
Whether planted as a single source of color and adornment or planted in a row to create a privacy screen, this beautiful sibling of the azalea is capable of fulfilling a wide range of functions. The main question on most people’s minds, however, is just how quickly do Rhododendrons grow?
Unfortunately, there is no single answer to this question. Rather it depends on the specific type of Rhododendron, of which there are over 800 species! This article will break down the four categories of plant size, allowing you to know which type is right for you.
Additionally, a list of optimum growing conditions will allow you to ensure you get the best results from whatever Rhododendron you choose to put into your garden.
Four Size Categories of Rhododendron
Due to the vast number of species and the variety of qualities they possess, it is impossible to classify Rhododendrons into a single category of size, shape and behavior.
However, they can be grouped into four different size categories, each reaching their maximum height in 10 years—the average time it takes a Rhododendron plant to reach maturity. These categories are as follows:
- Rhododendrons up to 1 foot in size
Otherwise known as miniature Rhododendrons, these variations rarely grow above 12 inches in height. Resembling ground cover more than the bushes or trees most people envision when they hear the name Rhododendron, they nevertheless produce the same vibrant and colorful flowers as their taller counterparts.
Miniature varieties include Rhododendron “impeditum”, which produces blue flowers, R. “Chikor” and “Little Lou” which produce yellow flowers, and R. “Cliff Garland” which produces the more traditional pink flowers.
Each of these only grows about 0.5 inches per year until reaching full height in 10 years.
- Rhododendrons up to 3 feet in size
The next category of Rhododendrons contains the varieties that grow between 1 to 3 feet in total height. These are used as ornamental plants in flower and rock gardens, and are commonly referred to as dwarf Rhododendrons.
Varieties in this category include Rhododendron “PJM Elite”, with purple flowers, R. “Baden Baden” and “Scarlet Wonder”, both producing bright red flowers and R.“Cappuccino” and “September Snow”, both with pink blooms.
These plants generally grow about 3 inches per year, reaching their maximum height of up to 36 inches in 10 years.
- Rhododendrons up to 6 feet in size
Anyone who wants to grow a hedge for privacy will probably choose one of the more common varieties of Rhododendron which grow up to 6 feet in total height.
These plants will grow as wide as they do tall, which makes them look like a cross between a tree and a shrub. Varieties of this category include Rhododendron “America”, “Burma” and “Nova Zembla”, each with bright red flowers, R. “Anah Kruschke” and “Cadis”, producing colorful purple flowers and R. “Furnival’s Daughter” and “Van”, bearing pink blossoms.
Each of these varieties can grow an average of between 6 to 8 inches per year, reaching full height in 10 years’ time.
- Rhododendrons over 6 feet in size
Finally there is the category of Rhododendron giants, any variety that grows over 6 feet in total height. The fact of the matter is that this category is the broadest, including trees that grow as high as 80 feet in total!
However, many cover the 8 to 10 foot range, making them more compatible with most gardening and landscaping needs. Varieties in this category include the red flowering Rhododendron “Caractacus”, the purple flowering R. “Whidbey Island”, the yellow flowering R. “Binfield”, and R. “Mother of Pearl” and “Mount Everest”, boasting bright white blooms.
Each of these types can grow as much as 1 foot per year, reaching 10 or more feet in a 10 year span.
Optimum growing conditions
As with any plant, regardless of type or size, maximum growth rates are only achieved when optimum growing conditions are present.
These conditions include sunlight, temperature and water, and only the right amount of each will allow any Rhododendron to reach its full potential. The best growing conditions for Rhododendrons include:
- Partial or gentle sunlight
All varieties of Rhododendron require at least partial sunlight to thrive. Morning sunlight is ideal, as it is less harsh than the afternoon sun.
In the event that afternoon sun exposure is unavoidable, plant your Rhododendron under tall trees whose limbs can provide decent shade from direct afternoon sunlight.
- Plenty of water
Rhododendrons are not suited for desert or arid climates. Instead, they thrive in wetter climates such as the Northeastern United States, Great Britain, and other areas where rainfall is abundant.
Since Rhododendrons have shallow root systems, mulch is recommended for helping to prevent the soil from drying out.
- Mild temperatures
While many hybrid varieties have been created in order to better survive more extreme temperatures, both in terms of heat and cold, most varieties of Rhododendron prefer a more moderate climate.
Additionally, they should never be used to provide a block against harsh winds as such conditions can cause serious damage to the plants. Make sure to check the hardiness zone rating on a plant to make sure it will thrive in your region.
Now that you know the answer for the question how fast do Rhododendrons grow? The different Rhododendron size categories you can make a better decision regarding which variety is right for you and your needs.
With a 10 year maturation rate, a good rule of thumb for determining how fast a particular plant will grow in a single year is to simply divide the maximum height by 10.
Finally, by ensuring that your Rhododendron has the optimum growing conditions you can help it reach its full growing potential, both in terms of size and speed.