Cultivar definition

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.

Rhododendron thomsonii portrait

Joseph Hooker found R. thomsonii in 1849 while exploring in Sikkim, India. Other plant collectors subsequently found this rhododendron species in Tibet, Burma, and Nepal.

R. thomsonii grows to be a small tree up to about 20 ft. tall in its native habitat, but it is unlikely to get more than half that size in cultivation. Typical height in ten years is about four to five feet.

R. thomsonii has attractive foliage. The leaves are two to four inches long, rounded or orbicular shaped. The new growth has a quite noticeable blue cast that becomes greener as it matures, eventually becoming dark green on the top of the leaf and lighter-colored on the underside.

On older plants, the reddish smooth bark begins to flake or peel and makes a beautiful contrast with the mixed brown, fawn, and pink new bark being exposed by the old peeling bark. This bark-flaking characteristic occurs not only on the trunk of the plant but occurs on the larger branches as well.

R. thomsonii is slow to flower. Flowers are 2-3" across, bell-shaped held in a loose truss of about 3-10 deep red flowers that have a contrasting large waxy cup-shaped calyx. This calyx can be whitish-green, yellowish-buff or greenish scarlet. The plant blooms in April.

R. thomsonii does best if planted in a location protected from the afternoon sun and late frosts.

Rhododendron 'Naselle'

Imagine corollas of rose-pink with yellow centers and orange spots formed into large trusses on a nicely rounded rhododendron. This is 'Naselle,' which is named after both a town and a river in the state of Washington. By the way, the word Naselle was derived from a Chinookan tribe named Nisal.

The cross was hybridized by Jim Elliot in 1987. The Award of Excellence was given to 'Naselle' in 1992.

Description of 'Naselle': The new leaves are pale maroon. When they mature, the leaves are medium green and elliptic. Each large truss holds up to 15 beautiful corollas of rose-pink with yellow centers and orange spots, and it has been described as one of the most striking of the 'Lem's Cameo' hybrids. This hybrid is well-branched and looks rounded in shape. It will grow into a four foot high by four feet (1.2 x 1.2 m) wide plant in ten years, and can tolerate temperatures to 0 to -5°F (-18 to -21°C). With respect to its optimal placement in a garden, it does well with filtered sunlight, but enough sunlight to produce those wonderful blooms.

Looking Forward to Spring

Let's see... it's the middle of March, 2020, and everyone is trying to cope with the coronovirus pandemic. In my area, garden club meetings, plant sales and spring flower shows have all been cancelled. And, of course, the annual American Rhododendron Society Convention, scheduled for late April, has been cancelled too. These are all things I look forward to every spring.

But, there's still lots to anticipate. I've already seen Rhododendron 'Seta', 'Cilpinense', 'Cornell Pink' and 'Christmas Cheer' (see blog; 'Early Blooming Rhododendrons') in bloom at my house, and it looks like 'Mary Fleming' will open on the next warm, sunny day. Rhododendron buds are swelling and so are the lovely companion plants like Erythroniums, Trilliums, and Bloodroot.

I am lucky enough to have a warm, protected deck and I like to bring containers up to enjoy from my kitchen window. I mix and match the display depending on the state of blooms, and it usually ends up being a riot of colour. The picture below is from my deck in mid April, 2019. I'm already looking forward to this year's display as I expect it to be every bit as bright and cheerful. So, since we're all staying home for awhile, we can putter around the garden and enjoy our own gardens' private spring shows.

 

ARS Celebrates its 75th Anniversary

The American Rhododendron Society celebrates its 75th Anniversary with a return to the Portland area, where the Society began in 1945, to present a group of world-renowned keynote speakers and tours to the Northwest’s outstanding gardens and nurseries. Informative guest speakers include Jens Nielsen, Kenneth Cox, Lionel de Rothschild and Steve Hootman. Outstanding garden tours are planned to the Crystal Springs Garden, the Cecil and Molly Smith Garden and the Lan Su Chinese Garden. The 2020 Convention will also feature a plant sale, photo exhibit/contest, and rhododendron science poster session.

The six chapters of ARS District 4 will host the 75th anniversary Convention, titled "2020 Vision, Looking Forward Reflecting Back" to be held at the Heathman Lodge in Vancouver, WA on April 29 to May 3, 2020, with optional pre-tour, April 27-28, and post-tour, May 3-5. Non-ARS members are invited and most welcome to attend.

Companion Plant: Mahonia

The Mahonias, or Grape Holly, are attractive plants, that are easy to grow, have evergreen leaves, bright flowers, colorful fruits that are not poisonous or injurious, and have few pests. From groundcover to low shrubs to stately background specimens, there is a Mahonia for nearly any place in the garden. The flowers are most always some shade of yellow, often fragrant, sometimes powerfully so. Berries, in clumps or pendulous clusters, are in the blue-purple-black range, and make good jelly. Foliage is leathery, pinnate, spiny to one degree or another, often red-tinted when young, and sometimes coloring purple-red in winter,

For the very smallest groundcover type, look for M. repens (Creeping Mahoni), a suckering form only 12 inches tall that's very tough. A bit bigger, to 18 inches, with shinier, longer leaves, and also a spring to early summer bloomer, is M. nervosa (Cascades Mahonia). Taller again, 4 to 6 feet or so, also suckering into thickets of stems and blooming May-June, is M. aquifolium (Oregon Grape).

 
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