Dogwood Lane


The Quarterly Journal of the Mary May Binney Wakefield Arboretum ___________________________________


Volume Seven Issue 1 - Fall 2024

The Mary May Binney Wakefied Arboretum Conifer Standouts

This edition of Dogwood Lane focuses on some of the more unusual conifers in the collection. They include Korean firs, Abies koreana, baldcypress, Taxodium disticum, Japanese cedar, Cryptomeria japonica and maidenhair tree or gingko, Gingko biloba. The Wakefield conifer collection has several different cultivars of each of these species that have unique characteristics and distinctly different forms. Polly Wakefield was interested in the variations that can exist within the same species and often sought out these features in dogwoods and other plants in her collection.

Cryptomeria japonica 'Cristata' are known for their "fascinations" or web footed contortions.

Japanese Cedar, Cryptomeria japonica

The Mary May Binney Wakefield Arboretum has several cultivars of Cryptomeria japonica including Cryptomeria japonica 'little heath', Cryptomeria japonica 'black dragon', Cryptomeria japonica 'Araucarioides', Cryptomeria japonica 'mushroom', and Cryptomeria japonica 'yoshino'. In 2020, the arboretum acquired two specimens of Cryptomeria japonica ‘Cristata’, Cristate Japanese Cedar. This cultivar is by far the most fantastic cultivar in the collection.


Japanese cedars are native to the mountainous regions of Japan. Their existence dates back centuries and they are common throughout Asia. Many cultivars thrive all over the country, the majority of them planted around shrines and temples as a sacred tree, considered a symbol of longevity and immortality. They were introduced to Europe and the United States in the early 19th century and quickly grew in popularity. Also known as the Crested Japanese Cedar, 'Cristata' was exported from Japan around 1900. This ornamental conifer can grow to 25’ in height and 15’ in width after many years. It features a slender, pyramidal shape. The needles are ½ to ¾ inch long, curving inward toward the twig they are borne upon. The foliage is usually a vibrant green but can turn brown during the winter. The bark is reddish and peeling. Like many Cryptomeria, it also is happy with most any cultural condition. An amazing fact about the 'Cristate' Japanese cedar is that the fascinations actually hold "true" when planted from seed.

Massive old Cryptomeria's planted outside a Temple in Japan. Photo by Debbie Merriam

Cryptomeria japonica 'Cristata' is very unique in appearance with fanlike structures gracing the tips of many branches. Of the many conifers that have been selected for fasciations (web-footed contortions) this is one that is very interesting, vigorous, and exceptional as a specimen or a container plant. The cultivar name ‘Cristata’ comes from the Latin adjective cristatus which, in turn, is related to fasciate. The noun, fasciation, describes the banded or bundled growth at the tips of the branches of a plant. Cristate means having a crest-shape, like the cockscomb on the head of a rooster.

According to an article published by the American Conifer Society, “Scientists believe that cristation, or fasciation, results in the tip of the branch growing outward, rather than growing farther along the stem. They attribute this fan-shaped growth to hormonal imbalance, insects, diseases, or physical injury to the plant. The strange growth is most likely caused by phytoplasma, which are bacterial parasites of the phloem tissue and of the insect vectors involved in plant-to-plant transmissions. The fan-shaped protuberance appears on many genera of plants: cacti, roses, and beefsteak tomatoes, to name but a few. As a consequence, since cristation is a cellular deviation, it may be the result of a genetic predisposition inherent in the plant, which causes division of growth and consequently that characteristic spreading-out at the tip of the branch.” (1)

The Wakefield's Cryptomeria japonica 'Cristata' were originally planted in the conifer collection behind the mansion house but soon were overshadowed by faster growing conifers. This fall horticulturalist, Ellen Scheid dug the plants and moved them to an area of the garden where they would have more light and space to show their unique characteristics. Now that we have relocated these conifers to a more public location of the arboretum our visitors often comment on their uniqueness. We look forward to their evolution in the garden.

Taxodium disticum golden foliage and cones. Photo by Marilyn Kircus

Baldcypress, Taxodium disticum


The Wakefield Arboretum has several baldcypress trees including the straight species Taxodium disticum and some dwarf cultivars. The first baldcypress was added to the Wakefield collection in 2015. Baldcypress has been planted far north of its natural range including Minnesota, and southern Canada. There are also several large old specimens in Buffalo, New York planted in the Olmsted designed landscapes. They are native to southern swamps and rivers from Texas to Maryland and are a commonly seen tree in the south. There are large groves of baldcypress growing in the median of the highways in Florida with their beautiful foliage and unique protrusions from the ground known as knees. These knees have been an object of study for centuries and a variety of hypotheses have arisen as to their function. According to an article written by Christopher Briand for Arnoldia. “Throughout the nineteenth century and continuing to the present, botanists have put forth hypotheses about the function of these peculiar formations. These hypotheses have included aeration of the root system, vegetative reproduction, mechanical support, nutrient accumulation, and carbohydrate storage.” (2)

Over decades several of these theories have been disproven and it appears that the current thinking is that the aeration theory may be the most widely accepted.

Knees of Taxodium distichum (baldcypress) located in the small wetland of Lake Lena at Meadowlark Botanical Gardens. Photo © Elaine Mills

Two of the baldcypress planted at Wakefield are just beginning to grow knees. The knees on some baldcypress have grown as high as ten feet tall and are thought to be related in size to the depth of the water that the trees grow in. The knees are formed on the upper surface of some of the shallow roots by the vascular cambium, the meristematic layer that produces xylem and phloem, the tissues that transport water and nutrients through the plant. Baldcypress and Dawn Redwood, Metasequoia glyptostroboides have a similar overall appearance, as both are in Cupressaceae, the Cypress family. Their macro-appearance is similar, but they can be distinguished by noting whether the leaves and branches are alternate or opposite. Baldcypress has alternately arranged leaves and branches, often referred to is the ‘ABC rule”: alternate bald cypress. (3)

The Wakefield collection has several cultivars of baldcypress that include Taxodium disticum 'cascade falls'. This weeping variety adds interesting color and texture to our conifer garden and is a very slow growing plant.

A gingko in Niagara Falls, Canada. Photo: Debbie Merriam

Maidenhair Tree, Ginkgo Biloba


The Wakefield Arboretum is home to a beautiful female gingko in the formal garden that produces a bounty of fruit every fall which creates a damp and smelly area around the base of the tree and over part of the lawn. The odor is recognizable from a hundred yards away. The smell is created by butyric acid that produces a rather putrid odor. (4).The gingko evolved to produce a fruit with this smell making it attractive to certain animals that would consume the fruit, digest the coating and excrete the seed that could then germinate.

Another interesting fact about gingkos is that they are classified as gymnosperms even though they have broadleaves like angiosperms. "This is because it produces naked seeds on its branches rather than seeds enclosed in flowers or fruit Its broad leaves also differ from angiosperms in having the ancient form of dichotomous venation rather than parallel (as in monocots) or netted (as in dicots). The ginkgo tree has sometimes been called “maidenhair fern tree” because of the resemblance of its leaves to those of the maidenhair fern, another early-evolved plant.” (5)

Gingko biloba 'snowcloud' in Wakefield's collection.

Variegated gingkos are sought by collectors for their unique character and interesting variegated foliage. The Wakefield arboretum has one called 'Snowcloud'. The new growth has more variegation then the older leaves. Many can prove difficult to propagate while maintaining the variegation. One common tactic is to prune out “reversions." While this method may be effective from time to time, some non-variegated branches may appear variegated the following year, while variegated branching may show no variegation the following year. It is still important, as with most variegated plants, to produce from plants that display the most stable variegation. Another method is to give variegated ginkgos more sun. Often variegated ginkgos lose variegation more quickly in shadier conditions than in sunnier growing conditions. At our nursery, we have played around with the idea of rooting variegated selections, but these same problems appear to affect both grafted selections and rooted selections.(6)

Female seeds on a gingko

Photo: Peter Del Tredici

Male flowers on a gingko

Photo: Kevin Nixon

"Male "flowers" (sometimes called pollen cones) are 2.5 cm long, catkin-like, with numerous stamens loosely arranged; female "flowers" are long stalked, 4-5 cm, solitary, with two opposing ovules at the end of the stalk. "Fruit" on female plants is actually not a true fruit but a naked seed (ginkgo is a gymnosperm = gymno, naked, and sperm, seed) with a fleshy covering (the sarcotesta), it is plum-shaped (ca. 2.5 cm diam.), green then tan or orange, extremely messy and malodorous when ripe." (7)


Korean Fir, Abies koreana


In 1919 Ernest Henry Wilson led an expedition to Eastern Asia to collect plant specimens for the Arnold Arboretum. Previous to this expedition not much was known about the flora of Korea, but it was thought that because Korea had a similar climate to New England, perhaps plants that thrive in Korea could also thrive in New England. This turned out to be true and the Korean fir was one of those plants collected. They are cold hardy and drought tolerant which made them a good choice for plant collectors.


Abies koreana, commonly called Korean fir, is a compact, conical to pyramidal evergreen conifer that grows slowly to as much as 50' tall. Branches are densely clad with short but broad needles (to 3/4" long) that are shiny dark green above and silver beneath. The silver beneath is actually the stomata on the needles. In botany, a stomata is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spaces of the leaf and the atmosphere. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that regulate the size of the stomatal opening. (8) Purple cones (to 3" long) are produced when the trees are quite young. As is distinctive with the firs, the cones appear upright on the branches.

Wakefield's collection has a lovely specimen of Abies Koreana 'silberlocke'.

'Silberlocke' typically grows as a compact pyramid to 8' tall during the first 10 years, eventually maturing over time to 20-30' tall. It features recurved needles which showcase the silvery undersides of the needles. This cultivar was introduced in Germany in 1986 by Gunter Horstmann.  Seed from this cultivar is reportedly true to type. The other stunning feature on this plant are the upright cones that start out green then turn purple then brown. Between May and June the female, purple flowers open, i.e. the cones, which have a cylindrical shape and consist of numerous seed scales. The male Korean fir cones are yellow and inconspicuous. What makes Korean firs so popular are their striking female cones. These grow up to 7 cm long and are a wonderful sight due to their dark blue/purple color with yellow-brown top scales. With age, the pine cones become dark purple to brown and covered in resin. Compared to other fir species, the Korean fir sets cones very early. This means young trees just 2 feet high can already form these beautiful cones.

Kohouts Ice breaker beginning to form a central leader.

Abies koreana ‘Kouhout’s Ice Breaker’ is a stand out of a silvery-white witch’s broom of Korean fir. Jorg Kohout of Elstra, Germany is noted for discovering it on a ‘Horstman’s Silberlocke’ Korean fir. It has intensely recurved needles that consequently expose their bright, shimmering undersides. As young plants, they are generally globose with their stubby, radial branches. Over time and without some judicial pruning, they tend to develop a leader and evolve into flashy, handsome, dense, squat pyramidal shapes. In most areas, typical growth rates are 1 to 3 inches a year. In 10 years, a specimen is often around 2 feet high and wide if a central leader is not involved. It is rated for USDA zones 4 through 7. In cooler zones, a sunny well-drained site brings out the best show for this extraordinary garden accent.

Footnotes


1.https://www2.conifersociety.org/blogpost/2082607/490261/Conifer-Fasciation-with-Cryptomeria-japonica-Cristata, Ron Abelardo

2.Arnoldia – Volume 60, Issue 4,Cypress Knees: An Enduring Enigma

Christopher H. Briand

3.ArnoldiaVolume 60, Issue 4,Cypress Knees: An Enduring Enigma

Christopher H. Briand

4. https://arboretum.harvard.edu/stories/stop-and-smell-the-ginkgoes, Ned Friedman

5. https://gardens.ucr.edu/news/2023/01/20/ginkgo-biloba#:~:text=Although%20it%20has%20broad%20leaves,enclosed%20in%20flowers%20and%20fruit. Ginkgo Biloba, Joanne Anderson

6.https://www2.conifersociety.org/blogpost/2082607/489791/Variegated-Plants-Ginkgo-biloba

7.https://landscapeplants.oregonstate.edu/plants/ginkgo-biloba

8.Annals of Botany, Stomatal Development in the Context of Epidermal Tissues.Keiko U Torii

We want to hear from you! We appreciate your feedback about our quarterly. Please let us know what research and articles you have found most interesting.

Articles written by Debbie Merriam and edited by Susan Hein and Ellen Scheid

For a printable copy of this or any prior issue of Dogwood Lane, click here or visit the news tab on our website.

Mary May Binney Wakefield Arboretum | 617-333-0924

1465 Brush Hill Road, Milton, MA 02186 | www.wakefieldtrust.org

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