QBARS - v30n4 Lime and Rhododendrons

Lime and Rhododendrons
Alleyne R. Cook, North Vancouver, British Columbia

In their notes on the use of lime 1 both Dr. Robert Tichnor and Dr. David Goheen stated that only gypsum should be used. This we have found is not correct. Ordinary agricultural lime is equally effective, and this over the past 30 years is all that we have ever used.
When a plant of R. 'Goldsworth Yellow' that was obviously dying was given a tremendous dose of lime just to see what would happen. The following spring we had a very healthy plant and so the entire nursery was given a topdressing of lime. This experience, and those that followed, were detailed in several articles in earlier bulletins. 2
In 1966 the collection of rhododendrons at the Royston Nurseries were brought by the City of Vancouver and moved to Stanley Park. They were planted in 10 beds but through the yearly creation of two to four new beds, and the thinning that is necessary, the area has expanded to about 40 beds. Each winter when the new beds were made, enough agricultural lime was spread on them to turn the ground white. This might have been done before or after the rhododendrons were planted. If the color of the rhododendron leaves were not up to the standard required, then during following years more would be applied. Of these 40 beds, seven were made from clay, three are pure peat, three the original soil with something dug in, and the remainder had 18 to 24 inches of partially decomposed leaves on top of the original soil. Nowhere has there been any harmful effects among the five or six thousand rhododendrons that we could observe.
For this reason and because of the length of time we have been using agricultural lime we feel that both gentlemen have made an incorrect statement.

1 Goheen ARS Quarterly 76-2
2 Ticknor ARS Quarterly Bulletins, 62-2; 63-1; 66-1