Gum Tree Structural Properties

Eucalyptus trees may live hundreds of years and change structure as they age.

Gum trees are native to Australia but grow in warm-season climates across the globe. They are known in most places as eucalyptus trees, the aromatic plants with high stature and oily leaves. The tree have two types of leaves. The juvenile leaves are oval, and the adult leaves are long and slender. The term "gum trees" refers to the sticky aromatic substance the tree secretes when it is wounded. Not all gum trees secrete this substance, but the name is still a general term for eucalyptus species.

Crowns

There are more than 600 species in the Eucalyptus genus, many of which have similar characteristics. The crown of a eucalyptus morphs as it gets older. The young plant has a widely branching crown that thickens and tightens as the tree matures. Trees younger than 100 years keep the original branches as the basic structure of the canopy. Older trees tend to lose these original formative branches and are comprised of newer tissue. The oldest trees have the highest portion of their total wood volume in the trunk, while the younger trees hold it in their crown.

Roots

Roots are the primary structural need of any plant. The gum tree's root system is designed to be widespread and grow rapidly. It must provide and collect water for 100-foot-tall trees and develops a strong, deep taproot that may go 6 feet into the earth to support the tree. The search for water causes the root system to spread out up to 100 feet, which makes it a pest plant when located near foundations or other structures.

Trunk

Eucalyptus trees are commonly harvested for their timber. The bark on many of them is shredded or strangely marked, with spots or irregular marks. Eucalyptus wood is strong and has a fine grain and texture. The wood is smooth and white and has a porcelain look. The trunks may be single-stemmed or multistemmed, depending on the species, but they are erect and straight. The base of the trunk is wider than the top and tapers to a smaller diameter as the tree grows.

Seed Casing

The structural development of the seed pod or casing in the gum tree is unique. It is urn-shaped and woody. The pod contains numerous seeds and chaff. The chaff is the cellulose material that keeps the seeds padded and helps them travel on the wind when they are released. Seeds mature inside the pod for up to 12 months until heat or the death of the plant causes them to be released. Each variety of eucalyptus produces a slightly different-shaped seed pod.

References

• Warra Long Term Ecological Research; Crown Architecture, Structural Attributes and Canopy Invertebrates of Eucalyptus Obliqua Trees; Jamie Kirkpatrick, et al.; 2002
• Natural History Museum: Gum Tree
• Australian Native Plants Society: Eucalyptus, Corymbia and Angophora - Background
• California State University, Stanislaus; The Eucalyptus of California; Robert L. Santos