Rhododendron Propagation at Wagner Nursery
Mrs. David Wagner, Woodburn, Oregon
Reprinted from The Plant Propagator
Since we root our own rhododendron liners, our first step is to produce a vigorous crop of cutting material on our mother plants. These shrubs are mature plants established in a lath house. In early spring all flower and terminal buds are pinched off in order to insure heavier lateral branching. A balanced fertilizer or organic fertilizer is applied along with needed insecticide and fungicide sprays, with regular watering through the summer months. These combined efforts result in an excellent supply of ideal cutting material by late summer; however, we have found that the optimum time for taking our cuttings is delayed somewhat since they're under partial shade.
Our propagation beds in the greenhouse are filled with 1/3 peat moss, 1/3 coarse sand, and 1/3 perlite. We find this mixture works well for us and gives excellent drainage. Before planting, the beds are thoroughly watered down and drenched with Morsodren fungicide solution. Our cuttings are taken from the end of August until the end of September, depending on the growing season. They are collected early in the morning, drenched in Morsodren solution and prepared in a cool room. Each cutting is cut to approximately 4½ inches in length and heavily wounded at the base. We try to retain as many leaves on the cuttings as possible, but cut them all in half and remove the center terminal buds. The bases are immediately dipped in a hormone powder containing indolebutyric acid. Next the cuttings are inserted in the beds in rows marked out with a planting stick bearing large evenly spaced spikes. This helps to insert the cuttings evenly and also leaves the hormone intact in the wounds. A time-controlled mist is used overhead and electric soil cables are maintained at approximately 70° F in the beds. Within a few weeks the cuttings start to callus and, by approximately December or early January, they have fairly nice root balls.
At this time the rooted cuttings are transplanted into prepared peat moss beds within the greenhouse. There they are left to commence further root development; top growth is then encouraged with the addition of heat and foliar feedings. The liners are gradually hardened off as spring approaches by airing the green house. Then, with weather permitting, they are planted directly into the open field.
Our growing fields are prepared at least a year or two in advance of planting. A five to six inch layer of sawdust is tilled into the soil, and periodic soil tests are made to establish fertility needs. Disbudding, watering, spraying, and fertilizing needs are carefully watched through the following growing seasons. Our objective is to produce large, healthy, well-branched, full-budded plants for wholesale trade. Although we are not a large grower, we are constantly aware that quality rather than quantity is our goal.