Curator’s Plant of the Month – December 2017

Picea cones

PICEA

Picea, or Spruce, is a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae and are found in the northern temperate and boreal (taiga) regions of the earth.

Spruce Tree

Spruces are large trees, from about 20–60 metres (about 60–200 feet) tall when mature, and can be distinguished by their whorled branches and conical form. The needles, or leaves, of spruce trees are attached singly to the branches in a spiral fashion, each needle on a small peg-like structure. The needles are shed when 4–10 years old, leaving the branches rough with the retained pegs (an easy means of distinguishing them from other similar genera, where the branches are smooth).

Spruce seedlings are most susceptible immediately following germination, and remain highly susceptible through to the following spring. More than half of spruce seedling mortality probably occurs during the first growing season and is also very high during the first winter, when seedlings are subjected to freezing damage, frost heaving and erosion, as well as smothering by litter and snow-pressed vegetation. Seedlings that germinate late in the growing season are particularly vulnerable because they are tiny and have not had time to harden off fully. Mortality rates generally decrease sharply thereafter, but losses often remain high for some years. “Establishment” is a subjective concept based on the idea that once a seedling has successfully reached a certain size, not much is likely to prevent its further development.

Picea cones

Spruce is useful as a building wood, commonly referred to by several different names including North American timber, SPF (spruce, pine, fir) and whitewood (the collective name for spruce wood). Spruce wood is used for many purposes, ranging from general construction work and crates to highly specialised uses in wooden aircraft. The Wright brothers’ first aircraft, the Flyer, was built of spruce.

Spruce is one of the most important woods for paper uses, as it has long wood fibres which bind together to make strong paper. The fibres are thin walled and collapse to thin bands upon drying. Spruces are commonly used in mechanical pulping as they are easily bleached.

The fresh shoots of many spruces are a natural source of vitamin C. Captain Cook made alcoholic sugar-based spruce beer during his sea voyages to prevent scurvy in his crew. The leaves and branches, or the essential oils, can be used to brew beer. The tips from the needles can be used to make spruce tip syrup. In survival situations, spruce needles can be directly ingested or boiled into a tea. This replaces large amounts of vitamin C. Also, water is stored in a spruce’s needles, providing an alternative means of hydration. Spruce can be used as a preventive measure for scurvy in an environment where meat is the only prominent food source.

Picea pungens ‘Fat Albert’ (Colorado Blue Spruce)

Spruces are popular ornamental trees in horticulture, admired for their evergreen, symmetrical narrow-conic growth habit. For the same reason, some (particularly Picea abies and P. omorika) are also extensively used as Christmas trees.

© 2019 Thorp Perrow