Deciduous conifers? Heresy you say! Indeed – there are trees that have needle like leaves and use cones as their fruiting structure, that drop their foliage each fall. I think that you may be aware of some of them but just never thought of them as conifers.
As a point of clarity, the term conifer refers to those trees that reproduce through the use of cones, and usually the trees have male cones that release pollen and female cones where pollination takes place and seeds are formed.
This article has been a long planned sequel to Footpaths’ most read article, “Identifying Evergreen Conifers”, which has been read over 3000 times, including 331 times last month. The difference between the two topics is that while there are about 650 species of evergreen conifers worldwide, there are only 15 species of deciduous conifers.
From an evolutionary standpoint, why would a few species of conifer trees develop the deciduous trait and drop their needles? After all, evergreen trees carry on photosynthesis all year long which would seem to be an advantage. It largely comes down to two hypotheses: That dropping needles may help the trees survive in regions with heavy snowfall, and it allows for immediate recycling of nutrients from the needles to make them available for the formation of new needles for the next growing season.
To best understand this discussion one has to have a basic grasp of plant taxonomy – how plants are classified. The broadest group is phylum, then class, then family, then genus, then species. As you progress through the groupings, members have more and more in common, until you get to the species level, where you have reached a unique organism. In scientific nomenclature, the first part of a scientific name is genus, and the second is the species. For example, the scientific name for the White Oak is Quercus alba. Quercus is the genus for the oaks. Alba means white.
The fifteen species of deciduous conifers can be broken down into two groups based on the plant family they are in – either the Cypress or Pine Family. In fact, three of the four genera (plural for genus) of deciduous conifers only have a single member. Meaning that the species is so unique that it can’t be closely grouped with other tree species.
The first two are members of the Cypress family: Bald Cypress and Dawn Redwood.
Bald Cypress (Taxodium distichum) is the only living member of the genus Taxodium, although one extinct species has been identified. It gets its common name from the fact that it is deciduous, going “bald” each fall. They can become massively large, reaching up to 150 feet in height with a trunk diameter of 6 feet. Due to its rot resistance, Bald Cypress wood was prized for uses that were exposed to the elements: fence posts, ship planking, barns, window frames, and doors.
Bald Cypress have a conical shape.
When we studied them recently at Spring Grove Cemetery and Arboretum in Cincinnati, they were “less bald” as the male cone flowering structures were starting to form in pannicles as noted in the photo above. The photo below shows a remaining female cone from last year and the new strands of male cones. The male cones will open to release pollen in March and April.
The mature female cone is roundish, marble size, and woody. The plates open to release the seeds.
The bark is gray to tan in color, somewhat smooth, and has an almost soft, felt feeling to it when touched.
The most notable thing about Bald Cypress are the knees that arise from the root structure. This is commonly seen when they grow in wetlands but is not as common when growing on more dry terrain. The true function of the knees is unknown, but hypotheses include providing stability in the unstable wetland soils, and to augment respiration that is inhibited by saturated ground.
The other member of the Cypress family is Dawn Redwood (Metasequoia glyptostroboides), which is the Asian cousin of the Bald Cypress and native to China. Like the Bald Cypress, it is the only member of its genus, Metasequoia. It has similar shape and needle structure to the Bald Cypress.
It is frequently planted in parks and has a female cone similar to that of the Bald Cypress – woody, round, and having plates. When we saw it last week at Spring Grove Cemetery, it too was showing the development of its male cones. In the photo below there are pannicles of this year’s male cones, and two female cones from last season.
Its bark is also smooth and somewhat soft, but can have a slight red tint to it, which may help distinguish it from Bald Cypress.
It is a popular landscape tree because it grows rapidly and its fine needles really do not need raking up.
I have pointed this out before but it bears repeating here. For me the easiest way to differentiate Bald Cypress from Dawn Redwood is how the needles and small branches arise on the tree. They arise alternate along the stem in Bald Cypress, while they arise opposite on the Dawn Redwood. How do I remember that? The American tree, Bald Cypress, is alternate (A=A). The Chinese tree (from the Orient), Dawn Redwood, is opposite (O=O). The difference can be seen in these side by side photos.
Bald Cypress (alternate) and Dawn Redwood (opposite)
The other pair of deciduous conifers are from the Pine Family: the true Larches and the False Larch. The true Larches are of the genus Larix, while the False Larch, also known as the Golden Larch is from the genus Pseudolarix. In scientific nomenclature the prefix pseudo means “false”.
There are 10 to 12 species of Larch trees that occur across the world and for the most part they are named geographically: Siberian Larch, European Larch, Himalayan Larch, etc. In North America there are 3 species: Eastern Larch, Western Larch, and Subalpine Larch. Unfortunately, the Eastern Larch (Larix laricina) is more often called the Tamarack tree. Unfortunate because it is confusing. Tamaracks are only native to North American, extending from Newfoundland in Canada to the Yukon in Alaska, and down into the upper Midwestern states and New England. They are seen further south as landscape trees, as at Spring Grove Cemetery, and the full range can be seen in green on this map. The name “tamarack” originated with the Algonquian peoples and likely means “wood used for snowshoes”. Appropriate given the geographic distribution of the species.
When compared to the Bald Cypress and Dawn Redwood, the Larch trees in winter still look somewhat cluttered despite having lost their needles. They have clusters of small branches that frequently have several years of old cones present, adding mass to the tree. Larch cones are typically less than an inch in length. At first glance it looks like any evergreen tree that has died. But of course it has not died, and like other deciduous trees, will green up in the spring with new needles.
Tamarack trees, and all members of the genus Larix, have a unique and easily identified leafing structures with their needles arising in a whorl from little pegs along the branches.
Those pegs can be better seen on this winter photo below that also shows the small cones from last season. So if in the winter you see a tree with pegs on its twigs and cone structures, it is likely from the Larch family.
The final deciduous conifer is the False Larch (Pseudolarix amibilis), which is also known as the Golden Larch. Like the Bald Cypress and Dawn Redwood, it is the only surviving member of its genus, while there are two extinct False Larch species. It is native to a limited range in eastern China and has only been planted in a few arboretums in the U.S. It was not available at Spring Grove for study. Like the larches it has pegs that are noted on the twigs in winter.
But when its grass-like needles are present they are easily differentiated from the needle like leaves of the true larches.
Also, the cone for the False Larch is larger than the true larch’s cone, measuring three inches. It has a rather disorganized appearance – like a kids craft project gone awry.
So the take home message on the deciduous conifers is that they are a curve ball that nature has thrown at us. Through evolution they have gone their own way and for the most part are unique, somewhat isolated specimens. But they have been around a long time. All four genera discussed here are considered prehistoric trees dating back 50 million years or more. Two, the true Larches and the Bald Cypress, are fairly common in natural areas in North America, whereas the other two are generally limited to landscape plantings. All four are known for their beautiful golden color in the fall. In addition, all four are popular bonsai trees. But the question remains, do I have time for another hobby?
Photos by Peggy Juengling Burns with the following exceptions:
The foliage photos of Bald Cypress, Dawn Redwood, and False Larch were from the iNaturalist website.
Winter False Larch photo from North Carolina Extension Gardner website.