How to select rhododendrons
 

By Ron Knight


THE RHODODENDRON IS RIGHTLY CALLED “THE KING OF SHRUBS”. Many gardeners think that rhododendrons are the most beautiful of any shrubs. Flowers come in red, pink, white, purple, yellow, orange and all shades in between. There are varieties that bloom on the West Coast in every month, from February through July. Some blooms have colourful blotches, speckles, frilled petals, or two-tone flowers. Leaves vary from fingernail size to half a metre and can be variegated, chartreuse, maroon, or greyish-blue. Some leaves have fuzzy orange or grey undersides. Plants can be obtained that are dwarf (under 60cm/2’), low growing (to 1m/3’), medium (1.3-1.6m/4’ to 5’), or taller when mature. There are rhododendrons that can grow in full sun; however most prefer some shade in the hottest part of the day. Truly, rhododendrons can enhance any location in any garden.


Homeowners who are merely looking for one or two nice rhododendrons to add variety to a perennial garden will find them at any retail nursery. Selection is easy; simply look on the labels for colour, bloom time, and size information. Remember that most rhododendrons will grow at least as wide as they are tall, so plan for adequate spacing between shrubs. Choose plants that are bushy, have dark green leaves, and preferably some new growth.

All Rhododendrons are Not Created Equal


For gardeners who want to start a serious rhododendron collection, with both hybrids and species and some rare and unusual specimens, there is much more to learn. And perhaps the most important lesson is this one: Although all rhododendrons are great-looking plants, there are both mediocre and superior varieties.


Mediocre rhododendrons have average-sized green leaves, average-sized flowers, and average ratings from the American Rhododendron Society (ARS). They usually won’t elicit a “WOW!” from any garden visitors except those from Eastern Canada. This doesn’t mean that mediocre-looking rhododendrons are worthless. For example, there are cold-hardy varieties such as ‘Bric-a-Brac’ and ‘Olive’ that bloom in mid-winter in BC. Although they have smaller, unspectacular flowers and leaves, in February when few other shrubs are blooming, they’re winners!


For most of the spring season, however, it’s more rewarding to have spectacular rhododendrons in the garden that have gorgeous blooms as well as other things going for them such as fragrance or bronze winter foliage. And the good news is that superior varieties, because they’re usually priced by pot size (a really dumb system), cost no more than the mediocre ones.


Unfortunately, most garden centres carry a majority of mediocre rhododendrons and a few superior varieties. The reason is that many of the large wholesale nurseries that supply our local garden shops are producing plants for the entire North American market. As a result, they like to propagate varieties that are extremely cold hardy, sun tolerant, and easy to root. Regrettably, these characteristics often come at the expense of showy flowers and leaves, making some superior rhododendrons less desirable to wholesale growers. But luckily, the Pacific Northwest is rhododendron heaven and almost all rhododendrons can be grown successfully here. The challenge, however, is to know which garden centres carry the highest percentage of superior rhododendrons and then to identify and ignore the mediocre varieties, especially when they’re not in bloom. 

Where Can You Buy the Best Rhododendrons?


Two clues will tell you whether a garden centre is really serious about rhododendrons as opposed to one that merely orders an assortment of colours and sizes:


1. Is there a written availability list?

 


2. Can the rhododendron buyer give you information about each variety, beyond what is printed on the label? Could this person answer a question such as, “Which of your rhododendrons do you consider to be superior and why?”



If you are looking for species rhododendrons, or for rare and unusual hybrids, your closest source is the Vancouver Rhododendron Society (VRS). This group of rhododendron enthusiasts has access to rhododendrons that are not usually available from local nurseries. Indeed, some of their members actually travel to Asia on seed-collecting expeditions. VRS members meet on the third Thursday evening of each month (except December, May, June, and July) at Van Dusen Gardens.  Visitors are always welcome. Rhododendrons are sold at each meeting and at their Spring Sale and Show on the first weekend in May. Go to the VRS web site for more information.

How Can You Tell Which Rhodos are the Superior Ones?

In order to find out which rhododendrons are superior, your best reference is a paperback copy of “Greer’s Guidebook to Available Rhododendrons” (H.E. Greer, 3rd edition, Offshoot Publications, Eugene, Oregon, ISBN 0-910013-05-5). It contains detailed descriptions of hundreds of different rhododendrons, both species and hybrids, as well as ARS ratings, awards, and codes indicating hardiness, size, and bloom time. When you have located a serious rhododendron nursery, you could take Greer’s book with you and use it to separate the mediocre from the superior rhododendrons on site. Be prepared to spend at least an hour on this task and take a helper with you if possible.


A better alternative is to prepare a wish list, using the nursery’s availability list, before your shopping day. The availability list should give details about colour, size, and bloom time for specific named rhododendrons. Check off the varieties that look interesting and then look them up in Greer’s Guidebook. Read Greer’s description, see how the rhododendron is rated by the ARS, and check whether it has received an award anywhere in the world.

This information, although not infallible, is better than the information listed on nursery plant labels. Realize however, that a rhododendron that is judged to be superior in one area, may seem mediocre in a less favourable area. However, you can be reasonably certain that the vast majority of rhododendrons that are highly rated by Greer will do well on the West Coast.


As a double check, you will find the American Rhododendron Society web site to be very helpful. Under “Rhododendron Plant Search Options”, it lists Proven Performers which have been submitted by several ARS chapters in BC. If a rhododendron you find interesting is on these Proven Performer lists and is also highly rated by the ARS, you will know you have located a winner. Following is a list of hybrid rhododendrons that have very high ARS ratings and are also Proven Performers in B.C.:


‘Olin O. Dobbs’, ‘Hallelujah’, ‘Crimson Pippon’, ‘Ken Janeck’, ‘Lem’s Monarch’, ‘Horizon Monarch’, ‘Curlew’, ‘Ginny Gee’, ‘Patty Bee’, ‘Fantastica’, ‘Mrs. Furnivall’, ‘Lem’s Cameo’, ‘Nancy Evans’, ‘Point Defiance’, ‘Paprika Spiced’, ‘Scintillation’, ‘Taurus’, ‘Grace Seabrook’, ‘Halfdan Lem’, and ‘Hotei’.


Now that you understand how to select superior rhododendrons, you may want to learn how to plant and care for them and how to place them in your garden using basic design principles. Consider taking Caron Gardens’ workshops on “How to Grow Great Rhododendrons” and “Selecting and Designing with Rhododendrons”.


'Patty Bee - This SPA-winning dwarf rhododendron

is completely covered with yellow flowers in April.

It is also a Proven Performer in BC.


Image © Ron Knight

Even though 'Olive' has mediocre flowers and leaves, she's a winner in February when few other shrubs are in bloom.


Image © Ron Knight

'Lem's Cameo' is called the "Queen of Rhododendrons".

It's one of a very few rhodos to win a Superior Plant Award (SPA) from the American Rhododendron Society.


Image © Ron Knight

These species rhododendrons have orange indumentum on the undersides of their leaves which adds colour to the winter garden.


Image © Cameron Knight