white spruce

(Picea glauca)

               
Conservation Status

IUCN Red List

LC - Least Concern

 

No image available

NatureServe

N5 - Secure

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

FACU - Facultative upland

Midwest

FACU - Facultative upland

Northcentral & Northeast

FACU - Facultative upland

Nativity

Native

Occurrence

Common

Habitat

Moist or dry. Moderately shade tolerant.

Pollination

Early May to early June

     
Height

30 to 60

     

Identification

This is a large, moderately slow-growing, evergreen, coniferous tree. It rises on a single trunk from a taproot, shallow horizontal roots with sinker roots, and shallow fibrous roots. It is moderately long lived, often surviving 100 to 250 years, with older individuals reaching 300 years of age. In Minnesota mature trees are usually 40 to 60 tall and up to 24 in diameter at breast height. The tallest trees may be more than 100 tall and 33 in diameter.

The crown is narrowly cone-shaped, relatively uniform, and dense. In open areas the crown extends well down the trunk. In crowded areas the lower branches are self-pruning and the crown is limited to the upper half of the tree. The trunk is straight and distinct to the top of the tree.

The bark on young trees is light gray or light grayish-brown and smooth or slightly rough at first. It soon breaks into small, flaky scales. On mature trees the bark is gray, darker, and broken into thin, irregular scales. The scales are closely appressed and do not curl outward at the top and bottom. On older trees the scales are thick. The inner bark on mature and older trees is salmon pink and silvery.

The branches are mostly horizontal and whorled, with each whorl representing one year of growth. The tree’s age can be determined by counting the number of whorls from the bottom up. Smaller branches develop between the whorls. Upper branches are ascending. Lower and middle branches are horizontal or slightly drooping.

First year twigs are slender, yellowish-brown, shiny, and hairless. They are sometimes covered with a whitish, waxy coating (glaucous). They do not hang downward (droop). Second year twigs are brown and may be tinged with orange, pink, or purple. The buds are egg-shaped, to ¼ long, and rounded at the tip. They are covered with many overlapping, orangish-brown, scales.

The needle-like leaves are bluish-green and are arranged in a tight spiral pattern around the twig. They spread in all directions from the twig. They are evergreen and remain on the tree 7 to 10 years. When crushed they emit a pungent odor that has been compared to cat’s urine. Each needle is to long and 1 32 to 1 16 wide. It is borne singly on a peg-like base that persists after the needle is shed. It is stiff, sharply pointed, straight or slightly curved, 4-angled, and square in cross section. It rolls smoothly between the thumb and forefinger. There are two whitish lines of minute openings (stomata) on each surface. Each whitish dot (stomate) is a pore surrounded by two glaucous guard cells. The guard cells control the size of the opening, allowing the exchange of gasses and water vapor.

Male and female cones are borne on the same tree. New cones are produced every year. Pollen (male) cones appear in the lower half of the crown. They are borne in groups at the base of one year old (second-year) twigs or singly near but not at the tip of the twig. They are red and succulent when they first emerge. Mature cones are dry, yellow, oblong, and 5 16 to long.

Seed (female) cones appear in the upper half of the crown. They are borne on leaf axils or at the tip of one year old (second-year) twigs. They are green at first. As the cone becomes receptive the scales turn red to green and the cone becomes erect. At the time of pollination the cones are ¾ to 1 long and the scales are widely spread. They reach full size in late June to early July, and maturity by August or September. Mature cones are brown, cylinder-shaped, 1 to 2 long, and hang downward. The scales are fan-shaped, widest near the tip, light brown, thin, and flexible. The margins of the scale are untoothed. Most seeds are shed in September. Seed cones can remain on the tree one or two years after most of the seeds have been shed.

Pollination takes place from May to early June. Male cones shed pollen then soon turn brown and fall away. Female cones mature in August of the first year and disperse most of the seeds in September.

 
Similar
Species

Balsam fir (Abies balsamea var. balsamea) has a narrowly pyramidal crown. The bark is not scaly but smooth except for raised resin blisters. The needles are longer and are attached flush with the twig. They are flattened in cross section, and do not roll easily between the thumb and forefinger. On lower branches they are often twisted at the base causing them to appear two ranked. The female cones are much longer, 1¼ to 3 long.

Black spruce (Picea mariana) has a narrow, spire-like crown with short branches. The middle and lower branches are greatly drooping with upturned tips. The twigs are covered with short, stiff hairs. The needles are shorter and blunt tipped. Mature seed cones are shorter, no more than 1¼ long.


Distribution Distribution Map   Sources: 2, 3, 4, 5, 7, 8, 28.

Record

The champion white spruce in Minnesota is on State of Minnesota property in or near Little Fork, in Koochiching County. In 1974 it was measured at 130 tall and 126 in circumference (40 in diameter).

 
Comments

This is the provincial tree of Manitoba.


Taxonomy

Family:

Pinaceae (pine)

 

Subfamily:

Piceoideae

 
Synonyms

Pinus glauca

Picea canadensis var. glauca

Picea albertiana

Picea glauca var. albertiana

Picea glauca var. densata

Picea glauca var. porsildii

Picea canadensis

 
Common
Names

Black Hills spruce

Canadian spruce

cat spruce

skunk spruce

western white spruce

white spruce


 

 

 

 

 

 

 

 

 

Glossary

glaucous

Pale green or bluish gray due to a whitish, powdery or waxy film, as on a plum or a grape.

 

stomate

A minute, epidermal pore, surrounded by two white guard cells, that allows the exchange of gasses and water vapor. The guard cells control the size of the opening.

       

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White Spruce

 
     
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Published on Jun 2, 2013

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-How to identify a white spruce

 
     

 

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