Conifer Cultivars

A recent trip to the Oregon Garden was a great opportunity to see a great variety of conifer cultivars. Many of the conifers you find in landscaping are cultivars of naturally growing species. What is a cultivar? "Cultivar" is a short version of "cultivated variety." It is a plant selected for some set of desirable characteristics, often a result of careful breeding to accentuate those characteristics. Most garden plants and food crops are cultivars.

There are only about 600 species of naturally growing conifers. However conifer cultivars number in the thousands. The Encyclopedia of Conifers describes over 8000 cultivars. The authors note that there may be over 15,000 conifer cultivars now.

Dwarf cultivars - All photos from the Oregon Garden

Cultivar names: The formal names of cultivars are formed by adding a special name to the Latin name of the species. These names can be in any language and are enclosed in single quotations marks, for example: Picea glauca 'Pendula', a cultivar of white spruce. Cultivars often have common names as well, in this case, weeping white spruce.

Picea glauca 'Pendula'

Variability: Cultivars can look entirely different from their parent species. Like the variety of dogs "cultivated" from the wolf, there may be hundreds of different cultivars developed from a single species of conifer. Over 450 have been produced from one Oregon native: Port Orford cedar (Chamaecyparis lawsoniana). Western red cedar has produced over 40 cultivars.

Origin: Many cultivars originated from naturally occurring genetic variations in a species or from genetic mutations. Others are produced by bud mutations on a normal tree. These can result in color change, different growth patterns, or dwarfing. Bud mutations often produce witches' brooms, a reduced growth form that creates a mass of short branches that often look like a dense bush growing high in a tree.

Cultivars are often reproduced by cloning, for example by growing cuttings taken from a twig. Some are reproduced from seeds, but normal reproduction introduces genetic variability that is often difficult to control.

Cupressus glabra 'Raywood's Weeping'
- a cultivar of Arizona cypress

Features: Conifers often grow to be large trees, not suitable to a small landscaped yard or garden. Many conifer cultivars are dwarfs compared to their parent species. They have been selected because they grow slowly and remain a reasonable small size for years. Many are selected for their unusual color, often showing blue or variegated leaves. Some show unusual growth patterns that people find attractive. A favorite feature is stringy, drooping branches. These cultivars are often named 'Pendula' or 'Weeping'.

One of the best places to see conifer cultivars is at the Oregon Garden. The Conifer Garden there features an extraordinary variety of cultivars that are beautifully landscaped and maintained. Fall and winter is a great time to visit. The conifers look about the same as in spring and summer, and you will avoid the crowds of people. 

Sequoiadendron giganteum 'Pendula'
 - a cultivar of giant sequoia

Abies koreana 'Silberlocke' - a cultivar of Korean fir

Abies koreana 'Piccolo' -  a cultivar of Korean fir

Cedrus atlantica 'Glauca Pendula' - Stretches across the photo and over the trellis

More info
Encyclopedia of Conifers [Caution: Extremely heavy. Lift with legs, not back.]
Bert Cregg: Extension Publications and Conifer Corner articles 

Bristlecone Pines: The Oldest Living Tree

On our recent trip to California, my wife and I drove up to Schulman Grove in the White Mountains to see the ancient bristlecone pines. Specimens of the Great Basin bristlecone pine (Pinus longaeva), are the oldest living trees in the world. These bristlecone pines have needles that grow in bundles of five. The needles are short for a pine, only about one inch long and spread along the branch like a bottle brush. However, these short needles live a long time, lasting up to 43 years. The cones are about three inches long. The growth form is often contorted and gnarled. Old trees have colorful, exposed wood that has lost its bark. Great Basin bristlecone pines grow at elevations over 10,000 feet in the White Mountains of California, and to the east in the mountains of Nevada and Utah. 

In 1953, Edmund Schulman discovered the world's first known 4000-year-old tree in the grove of bristlecone pines now called Schulman Grove. He used an increment borer to get samples of the growth rings of many of the bristlecone pines in the area and discovered one that was over 4700 years old. The oldest known living tree is another bristlecone pine that is over 5000 years old (5060 years old in 2012). It is growing at an undisclosed location, about 12 miles north of Schulman Grove.

Schulman Grove is located 24 miles from Big Pine, California. The road to get there is paved, but steep and winding. There is parking at the Ancient Bristlecone Pine Forest Visitor Center, where you can hike three trails at Schulman Grove. There is no water to be had in lake, stream, spring, or well, which tells you something about the arid nature of the White Mountains, and should suggest something about the nature of the bathroom facilities located near the Visitor Center. I hiked around the mile long Discovery Trail loop to get the photos shown here.

Tree-ring dating
It's easy to determine the age of a tree by counting the annual growth rings after it has been cut down. A less destructive way is to use an increment borer. This device is a long hollow drill bit that can extract a thin cross section of a tree, which enables you to count the tree rings. Also, since the rings are wider in wet years, you can determine variable weather patterns throughout the history of a tree. Furthermore, this variability forms patterns that researchers can recognize in different core samples. By comparing cores from living trees with cores from dead trees and wood fragments, researchers can extend their knowledge of weather patterns back for thousands of years. We now have a continuous record of bristlecone pine tree rings going back over 11,000 years. Also, tree rings in the wood at archaeological sites enable scientists to determine the age of the wood.

Since the tree rings provide an accurate count of the years, this research has enabled scientists to calibrate the readings from radiocarbon dating, giving archaeologists all over the world more accurate data on the age of artifacts.

Gray Pine

I was at the Portland Chapter meeting of the Native Plant Society recently and someone there told me that the gray pine (Pinus sabiniana) was an Oregon native. This was news to me. It’s not listed in Trees to Know in Oregon, from the Oregon State University Extension Service. Also, Ronald Lanner writes in Conifers of California that gray pine is “…a native to California alone – without any Nevada or Oregon outliers.” (p. 71) He goes on to quote David Douglas on the discovery of the gray pine: “I have added a most interesting species to the genus Pinus, P. sabinii, one which I had first discovered in 1826, and lost, together with the rough notes, in crossing a rapid stream.” However, David Douglas was not in California in 1826. He was in the Umpqua Valley area of Oregon in search of sugar pine, where he must have also seen some gray pine. The “rapid stream” he crossed was the Santiam River.

Frank Callahan documents the discovery of the gray pine in Oregon. He reports that a railroad survey in 1855 recorded them growing in Jackson County between Gold Hill and Central Point. In 1945, Oliver Matthews provided the first scientific documentation of Pinus sabiniana in Oregon after collecting specimens near Gold Hill. Callahan notes numerous specimens that he has located in the Medford area.  (See Frank Callahan, “Discovering Gray Pine (Pinus sabiniana) in Oregon,” Kalmiopsis Volume 16, 2009.

The gray pine is a distinctive pine with long, gray-green needles. Its most distinctive feature is the size of its large, heavy cones. They are usually visible it the top branches of the tree, where they remain for several years after they mature. The cones have the largest seeds of any conifer in the Pacific Northwest. The nutritional seeds were harvested by Native Americans, although too few trees grew in Oregon for them to be an important food source. Since the seeds are too large to be dispersed far from the tree, the gray pine relies on birds to disperse the seeds. Gray pine seeds are a favorite food of the Steller’s jay and scrub jay, which store seeds in the ground to eat later. Since the jays never recover all the seeds, they also plant the next generation of gray pines.

For more information, see Northwest Conifers.