Article Copied from the American Rhododendron Society Blog
Print date: 5/14/2021
11 September 2020 @ 16:50 | Posted by Bruce Palmer
Cultivar is a hybrid word constructed from cultivate (from Latin cultus, to care for or cultivate) and variety (from Latin varietas, absence of monotony). A cultivar is a plant type that has been propagated to show specific characteristics reliably over time.
Crossbreeding or hybridizing is the most common method for creating cultivars. Hybridizing two plants results in a large variety of genetic recombinations, called a "grex" for short. More commonly, the results are called "sister seedlings".
Usually the hybridizer wants a consistent set of characteristics to be repeated over a long period of time. Seeds will not do very well, though some seeds, particularly for vegetable gardening, are called cultivars. For plants like Rhododendrons, we want to be sure each plant has the exact characteristics the hybridizer chose.
To get them, they can be propagated several ways. The easiest for the amateur is to grow cuttings. By taking shoots of a desired plant and raising them in a soil mixture until they are safely rooted, it is possible to get a fairly large number of plants that are alike.
A more difficult method that can produce huge numbers of identical offspring is meristem culture. In meristem culture, unspecialized cells from buds are shaken apart and grown separately to produce entire identical plants. This is definitely not a method for the amateur. but it used by many nurserymen to get hundreds of one specific cultivar at the same time.
Another way to get a desired cultivar is by grafting, although the method is seldom used anymore. The method gets good, healthy plants that bloom well, but there is a major drawback. Rhododendron ponticum from Central Europe previously was used as the stock plant for grafting rhododendrons. Eventually the stock plant has a tendency to produce shoots from below the graft, slowly out-competing the grafted plant. The same problem occurs with grafted roses and a number of other grafted plants.
There are some other ways to get a cultivar, including air layering or ground layering, but generally the easiest way for most of us to get a particular desired cultivar is to buy it from a nursery.