Trees on the Yale Nature Walk

Pin Oak
Quercus palustris
Tree ID: 37
Hillhouse
Date of tree entry: April 20, 2015
The pin oak refers to a red oak (Genus, Quercus; Section, Lobatae) of the Fagaceae Family. Plants of the Fagaceae family are distinguished from otheres by their simple leaves with pinnate venation, monoecious (i.e. hermaphroditic) reprodcutive capacity, and cupule-shaped fruits. The fruit of Quercus palustris is the acorn, roughly 15,000 of which will be produced by any given Pin Oak each year. The pin oak is also deciduous, meaning that it will abscise, or shed, its leaves each fall after dropping its zygote-bearing acorns. Oaks undergo abscission for a number of reasons; the pin oak does so to conserve water and nutrients during the drier seasons. A majority of water and nutrients taken up by the tree's vascular transport tissues are absorbed by the leaves, and the process demands incredible energy expenditure. Relative to other deciduous trees, the pin oak is medium-sized at maturity, reaching a full height of 18–22 meters. The trunk's diameter (base) can reach 1 meter and only rarely exceeds this size. My pin oak measures 22.3 meters in height, placing it among the tallest; trunk diameter is 0.79 meters. Growth proceeds slowly for the first 20 years - around the time acorn production begins - and thereafter accelerates markedly.

Black Locust (False Acacia)
Robinia pseudoacacia
Tree ID: 44
Prospect and Sachem
Date of tree entry: February 5, 2015
Although it may not have any of the familiar green pods we've come to know from the food aisle, the black locust tree belongs to the pea family, Fabaceae. It's native to the southeastern United States and also the lower slopes of the Appalachian Mountains. A deciduous tree with short, irregular branches and feathery leaves, the black locust grows fast but is short-lived. Black locust trees can reach heights of 70 to 80 feet but are more often 30 to 50 feet tall. The black locust bears toxic pods that hang from its branches, but it also has white, fragrant flowers that bloom in late spring. These flowers produce a delicious and much sought-after honey that bees love. The black locust doesn't compete well with other trees and isn't a big fan of shade, but it's nevertheless a resilient species. It grows quickly, can survive drought and harsh winters, and creates new trees by sending up new sprouts from roots and stumps.

Star Magnolia
Magnolia stellata
Tree ID: 40
Hillhouse
Date of tree entry: February 4, 2015
Magnolia stellata is a small tree native to Japan that can reach a height of 4.6 - 6.0 meters. It is a deciduous tree that has a twiggy appearance with small buds in the winter. Its common name, star magnolia, refers to its large, white star-shaped flowers which bloom anytime between late winter to early spring.

Callery Pear Tree
Pyrus calleryana
Tree ID: 33
Hillhouse
Date of tree entry: February 4, 2015
The Callery pear tree is a small decidious tree native to China and Vietnam. Look for its white flowers with an unpleasant odor in early spring.

Japanese Zelkova
Zelkova Serrata
Tree ID: 35
Hillhouse
Date of tree entry: February 4, 2015
The Japanese zelkova, is a deciduous tree that typically grows to a height of around 30m. It typically has a short trunk followed by many erect branches that continue upwards to create a round-topped head. You can differentiate these trees from an American Elm due to the Zelkova's unwinged fruit and symmetrical rather than uneven leaves.

Japanese Maple
Acer palmatum
Tree ID: 42
Hillhouse
Date of tree entry: February 4, 2015
Acer palmatum (common name: Japanese maple or smooth Japanese maple) is a species of woody plant native to Japan, North Korea, South Korea, eastern Mongolia, and southeast Russia. Acer palmatum is a deciduous shrub or small tree that is 20 to 33 ft tall. It is often present as an understory plant in shady woodlands. In nature, Acer palmatum undergoes considerable genetic variation. Seedlings from the same parent tree often grow to display differences in key traits such as the leaf size, shape, and colour. Development of Japanese maple cultivars started in Japan in the 1700s, when gardeners selected and bred or used grafting to propagate attractive variants in leaf features, and overall size and form of the tree. Currently, there may be more than 1000 varieties and cultivars present, including hybrids or grafts with species closely related to Acer plamatum, such as A. duplicatoserratum and A. japonicum (downy Japanese maple). Out of these, at least 350 cultivars are used in Europe and North America. The term “Japanese maple” does not represent one species and may be used to refer to any of the 23 species of Acer that are native to Japan.

American Holly
Ilex opaca
Tree ID: 39
Hillhouse
Date of tree entry: February 4, 2015
Tucked away a few steps from Hillhouse Ave this Ilex opaca is a pillar of Christmas time cheer amid a small group of deciduous and evergreen trees. American holly are unique in their vast range; they are native from southern Massachusetts to central Florida, and can be found as far west as eastern Texas. American holly are evergreen trees with small, white flowers and red berries. The berries are an important source of food for birds, and they are reputedly poisionous to humans.

Crabapple Tree
Malus x.
Tree ID: 32
Hillhouse
Date of tree entry: February 3, 2015
The crabapple is a small, deciduous tree found primarily in the temperate zone of the Northern Hemisphere. These trees typically grow to be 4-12 m tall, and possess distinct white, pink, or red petals when in bloom. Crabapples are self-sterile, and thus completely rely on insect pollinators to transport their pollen. Despite this, crabapples cross-pollinate often and have hybridized over generations to the point where a distinct species within the genus cannot be identified.

Blue Atlas Cedar
Cedrus atlantica
Tree ID: 31
Hillhouse
Date of tree entry: February 3, 2015
The Blue Atlas cedar, the most popular of all Atlas cedars, is a majestic evergreen tree, with limbs covered with patches of green or blue-green needles. In its early years of life, it maintains a narrow conical form before widening into a pyramidal form after around 20 years. In its natural range (the Atlas Mountains of Algeria and Morocco), it can grow up to 120 feet high and 40 feet wide. This particular specimen stands alone in a courtyard between Hillhouse and Prospect Streets, so it has the space it deserves. Compared to most conifers, the tree is very tolerant of heat and dryness.

White Fir
Abies concolor
Tree ID: 30
Hillhouse
Date of tree entry: February 3, 2015
The white fir is native to the mountainous regions of the Pacific coast to central Colorado, and from central Oregon and southeastern Idaho to northern Mexico. They can grow in a variety of environments, from high elevation with long, snowy winters to lower elevation with warmer weather and lower precipitation. It is a monoecious species, with densely grouped reddish male cones and larger brown female cones. It is a genetically adaptable and plastic species that has been known to hybridize with other firs. The white fir has two primary uses: in construction as timber, and as Christmas trees. As such, they are commercially grown and harvested. The biggest threat to the white fir are predatory animals. The fir engraver beetle, for example, can damage up to 2.4 million cubic meters of harvest stock per year. Rodents such as the pocket gopher and grazers such as deer can also stunt their growth, and in extreme cases, outright kill mature trees. Our specimen in New Haven serves an aesthetic rather than commercial purpose and seems to have thankfully remained safe from predators.

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