QBARS - v29n2 Retarding Rhododendrons

Retarding Rhododendrons
Arthur W. Headlam, Bentleigh, Australia

Do not be misled by the title, for no one wishes to retard rhododendrons, but nurserymen and exhibitors often find it necessary to retard the flowers when a rhododendron, perhaps perversely, decides that it is time to flower, often unfortunately some days before it is due on the show bench or in the nurserymen's exhibits at a show.
It is a well-known fact that light has a profound effect on flowers, without it they would be unable to grow, so the sudden curtailment of light and warmth for a short period immediately commences to retard the process of flowering. The opposite is achieved when a rhododendron is slow in flowering by bringing it into the light and warmth. Nature regularly produces late or early seasons and man steps in and tries to emulate what is usually controlled by natural changing climatic conditions, sometimes with a considerable degree of success.
The Australian Rhododendron Society's main show is held in early November, and at this time of the year, the commencement of our third month of Spring, the weather may be quite hot and force some rhododendrons into flower earlier than usual. To retard the flowers so they will reach their peak over the four days of the Show requires a degree of skill and judgment, not to forget of course, an element of luck. With the commencement of color showing in the buds, perhaps some eight to ten days before the Show, the plant, if in the ground, is lifted, balled in burlap and placed in a dark cool shed which immediately slows down the process of flowering The question is, when to again bring it out into the light and warmer atmosphere.
Usually, after careful examination and a considerable degree of speculation, it is brought out again some one or two days before the show, and if progress has been successfully assessed, the flowers will be at their peak at the critical time; if the flowers should open a little too early, usually no harm is done as the plant may be placed in a cool position where the flowers will retain their freshness for a week or more. Of course, there is always the chance of a cool change in the weather and the buds may not open in time.
Rhododendrons must not be given the 'dark room' treatment before the buds show color, otherwise bleached or pale looking specimens may result. For this reason some exhibitors prefer placing their rhododendrons in a cool, deeply shaded position, which also has the effect of slowing down the flowering, but without the possible disadvantage of spoiling the color. Withholding water also helps the slowdown process.
On the other hand, there are times when the flowers are somewhat reluctant to open, often in times of colder than normal conditions. One nursery has, on occasions, overcome this problem by sending the rhododendrons to a suburban depot at a considerably lower altitude, with consequently relatively higher temperatures. This has started the process of the buds opening, when they are returned to Olinda and duly become part of an exhibit in one of the annual shows. However, this procedure will only operate when there is a particularly cold winter at Olinda and a change in climate does the trick. A mild winter at Olinda results in earlier flowers in any case, so there is no advantage in a change of climate. Others find that moving balled plants to a glass house or sheltered area also has the desired effect of starting the flowers moving.
In all there appears to be no hard and fast rule. A procedure which will achieve a measure of success in one season may not bring the desired results in the next. It is generally necessary to process some three or four plants for each one to be exhibited.
Despite the somewhat unscientific methods used, and the inability of exhibitors to obtain a crystal ball, it is extremely gratifying to the Show Committee and visitors, that the nurserymen are able to stage year after year, attractive, colorful and pleasing exhibits which are one of the main attractions of our annual show.
We were pleased last year, to extend a welcome to Mr. and Mrs. David Goheen of the Portland Chapter. David was drafted as one of the judges of the Nurserymen's displays, the first prize being a shield duly engraved with the winners name each year.
Last year was a late season and nurserymen's main problem were to bring rhododendrons into flower for the show November 2 through November 5. Their endeavors in this direction were so successful that the judges had quite a task in choosing the winner as well as the second and third places.