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Picea glauca

life science Maturity 5-7 Next article →

The white spruce, known scientifically as *Picea glauca*, is a large evergreen conifer.

Picea glauca taiga
Picea glauca taiga

It plays a vital role in the northern temperate and boreal forests of North America. This species is found across a massive range in Canada and the United States. It stretches from central Alaska all the way to the eastern provinces. It reaches as far as the Avalon Peninsula in Newfoundland. In the south, it grows in places like Montana, North Dakota, and Minnesota.

Gaspé taiga
Gaspé taiga

It even survives in isolated pockets like the Black Hills of South Dakota and Wyoming.

As the tree grows, its physical shape changes quite significantly.

White Spruce, Brampton, Ontario (5322599282)
White Spruce, Brampton, Ontario (5322599282)

Young trees usually have a narrow, conical crown. As they reach maturity, the crown becomes more cylindrical in shape. The bark is relatively thin, usually measuring less than 8 mm thick. It is often grey-brown or ash-brown in color. This bark is scaly and tends to flake off in small, circular plates.

White Spruce bark detail, Chalco Hills
White Spruce bark detail, Chalco Hills

When the bark is freshly exposed, it can appear silvery.

The needles of the white spruce have a very specific structure.

A dwarf Alberta white spruce
A dwarf Alberta white spruce

They are needle-like and have a rhombic shape in their cross-section. The top side of the needle is a glaucous blue-green color. This term, "glauca," refers to that specific waxy coating. The bottom side of the needle is blue-white. This side contains two broad bands of stomata. Stomata are tiny pores that allow the tree to exchange gases. The shoots of the tree may be smooth or have fine hairs, depending on whether they are in the east or the west.

Reproduction in the white spruce relies on a complex process involving cones and seeds.

Picea glauca seeds pigl 001 php
Picea glauca seeds pigl 001 php

The tree produces pendulous, slender cones that hang downward. These cones start out green or reddish after pollination. Over the next 4 to 8 months, they mature into a pale brown color. A single cone can contain anywhere from 32 to 130 sound seeds. Each seed is quite small, measuring only 2 to 3 mm long. Every seed is attached to a slender, tan wing that is 5 to 8 mm long. This wing helps the seed travel through the air.

Seed dispersal is a process driven by moisture and wind.

Riviere Sautauriski PJC
Riviere Sautauriski PJC

In the late summer or early fall, the cone scales begin to reflex, or bend back. This happens as the moisture content in the cones decreases. Cones typically open when their moisture content is between 45% and 70%. Once open, the wind carries the winged seeds away from the parent tree. While most seeds fall nearby, some can travel more than 300 or 400 meters. Interestingly, cold and damp weather can cause the scales to close again. They will only reopen to release more seeds when the weather becomes dry.

The white spruce is also known for its highly adaptable root system.

Photograph of Nursery Stock at Cass Lake Nursery - NARA - 2128140
Photograph of Nursery Stock at Cass Lake Nursery - NARA - 2128140

The roots respond to many different environmental factors. These include soil moisture, soil fertility, and mechanical impedance, which is physical resistance in the soil. If the soil is shallow or limits how deep a root can go, the tree develops a plate-like root system. This is not a genetic requirement, but a response to the environment. In other areas, the tree grows several long, lateral roots just below the surface. The structure of the tracheids, which are water-conducting cells, even changes based on available nitrogen.

This species is remarkably long-lived and resilient.

Old Growth White Spruce in Whitehorse
Old Growth White Spruce in Whitehorse

On average, a white spruce can live for 250 to 300 years. Some trees in rigorous, harsh climates have been found to be over 300 years old. The tree also possesses a complex genetic makeup. It has three different types of genomes: a nuclear genome, a mitochondrial genome, and a plastid genome. Scientists published the large, 20 Gbp nuclear genome in 2015. This deep biological complexity helps the white spruce thrive across such a vast and varied landscape.

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🖼️ Images & Media (17)
File:Picea glauca seeds pigl 001 php.jpg
Picea glauca seeds pigl 001 php.jpg
Photograph of Nursery Stock at Cass Lake...
File:White Spruce bark detail, Chalco Hills.jpg
White Spruce bark detail, Chalco Hills.jpg
File:A dwarf Alberta white spruce.jpg
A dwarf Alberta white spruce.jpg
File:Picea glauca taiga.jpg
Picea glauca taiga.jpg
File:Mt Bigelow West Peak Maine.JPG
Mt Bigelow West Peak Maine.JPG
File:Extracts from reports on the district of Ungava, recently added to the province of Quebec under the name of the territory of New Quebec (1915) (14760113996).jpg
Extracts from reports on the district of...
File:Treeless bogs interspersed with spruce.jpg
Treeless bogs interspersed with spruce.jpg
File:Riviere Sautauriski PJC.jpg
Riviere Sautauriski PJC.jpg
File:Tall white spruce shade the mossy forest floor.jpg
Tall white spruce shade the mossy forest floor.jpg
File:White Spruce, Brampton, Ontario (5322599282).jpg
White Spruce, Brampton, Ontario (5322599282).jpg
File:Fireweed Yukon.jpg
Fireweed Yukon.jpg

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