Frequency of Watering and the Growth of Phalaenopsis
Gavino Rotor, Jr. and Russell C. Mott

Conflicting opinions prevail amongst orchid growers relative to the frequency and the amount of water for orchid plants under greenhouse conditions. This is undoubtedly due to the lack of precise experiments on which definite conclusions can be made.

The first of a series of experiments on the watering of orchid plants was started in the Department of Floriculture at Cornell on January 15th, 1949. The investigation is being continued and the results presented in this paper were obtained after one year of treatment. The plants used were 2-year-old hybrid seedlings of Phalaenopsis #232. We are indebted to Alberts and Merkel Bros. of Jacksonville, Florida for the plants used in the experiment.

Thirty plants were planted in osmunda fiber pots in 5-inch pots with a depth of 4 1/2 inches. The plants were carefully selected on the basis of uniformity of size and vigor. Six plants were used for each treatment and a total of five such groups were used. The treaments follow: group no. 1, constant water level; group no. 2 , watered daily; group no. 3, watered every third day; group no. 4 watered every fifth day; group no. 5 watered every tenth day.

When watered, a pint of water per plant was used in each treatment except for group no. 1. This amount of water was determined previously to be sufficient for wetting osmunda fiber in the 5-inch pot. The plants in the first treatment were placed in shallow pans which were always filled with water. The lower one-third of the pot was maintained immersed in water continuously. The fifth treatment in which teh plants were watered every tenth day represented the recommendation made by some orchid growers of drying plants thoroughly before every watering.

Contrary to popular belief, keeping Phalaenopsis plants wet was not harmful. In fact, the plants grew faster and produced larger leaves and more flowers with a constant water level and likewise daily watering. The minimum and maximum number of flowers produced in each treatment are as follows:

In Figure 1 representative plants at the flowering stage are shown for each given treatment. The differences in the growth and flowering were so marked that when the plants were placed side by side, there was a downward gradation in size of the foliage and length of the flower stalks with decrease in water. The tallest plants resulted

Figure 1

from the constant water level treatment while the shortest were those that received water every tenth day. In this latter treatment, the mature leaves were markedly shrived and flaccid. This is an unmistakeable sign of water deficiency and is the reason for the degeneration of buds and complete absence of flowers in two of the plants under this treatment and the low production by the remaining four plants.

Another interesting observation was made on teh root growth of teh plants. the plants which were surface-watered every third, fifth, and tenth day produced roots which remained on or close to the upper surface of the osmunda fiber. These roots eventually grew out of the pot and grew over the bench. The roots of the plants in constant water level and those which were watered daily grew into the osmunda fiber and remained inside the pots. A few of the roots which grew out of those pots partially immersed in water grew directly into the water and continued to elongate and live for a long time.

This experiment reveals that plants of Phalaenopsis not only tolerate but require an abundant and continuous supply of water for optimum growth and maximum flower production. The drying of plants before each watering is definitely harmful and is not to be recommended. - Department of Floriculture, Cornell University, Ithaca, N.Y.