Picea

The background of the Alberta spruce is a source of some disagreement. It is considered a south-western form of the white spruce (P. glauca), or perhaps as an intermediate form of a hybrid involving the Engelmann (P. engelmannii) and white spruces, which is what it undoubtedly looks like. The needles are longer than those of the typical white spruce, and the stems of the new growth are hairy, like the Engelmann.

At Mustila, a large stand of Alberta spruce grew for many years in the western part of the Arboretum, near the seasonal greenhouse, Näppäri. Their seed provenance was Crow’s Nest Pass in the Canadian province of Alberta, which is rather continental compared with Mustila’s climate. Like many of the Arboretum’s other exotic spruce plantings, with increasing age this stand has also suffered major insect damage. Currently there is only a small group of trees left. The same provenance has been used in the Finnish Forest Research Institute’s various test plantations, but fairly good results have been obtained only at Punkaharju.

In the year 2000 a small new stand of Alberta spruce, of Kirkup Creek, B.C., provenance, was planted in the spruce collection at Näppäri. Trees of this provenance have generally grown well at Mustila, and the development of these plantings is being followed with interest.

Sitka spruce grows along the west coast of North America from Alaska to California, and has many – sometimes surprising – merits. Few know that it was used in the building of one of the largest aircraft ever, Howard Hughes’ Spruce Goose, and also for the Mosquito aircraft used in the Battle of Britain in WW-II.

This majestic tree has been used throughout history by animals, plants and man. It grows to over 90 metres, and the trunks of giants blown down in Pacific storms provide an environment suitable for many species, including a new generation of Sitka spruce, which start life growing on these so-called nurse logs.

Sitka spruce migrated into North America from Asia during the Ice Age, across the then dry Bering Strait. It was unable to cross the Rockies into the drier hinterland, however, as it is completely dependent on moisture from the Pacific Ocean, which condenses on the huge trees’ needles and drips to the ground for the roots to drink. The species has been widely planted in Europe, e.g. in Scotland, but in Finland it has proved rather frost tender and can only be expected to survive on the southwest coast and in the archipelago. At Mustila there is only a single specimen left of those planted in the early 1900s.

Colorado spruce grows naturally in the southern Rockies of the United States, between 1800-3400m above sea level, together with Douglas fir (Pseudotsuga menziesii), Engelmann’s spruce (P. engelmannii) and Subalpine fir (Abies lasiocarpa), among others. It prefers open mountain forests and is quite happy on fairly dry sites. With its deep roots, it survives storms well. The needles often display the waxy blue-grey coating typical of many species of conifers from southern mountain zones.

Colorado spruce has a regular conical shape, and is very dense. Particular when young, the crown is attractively layered. The sturdy branches grow horizontally. A good tip for recognising this species are the particularly stiff and sharp needles, which are quite long, curved, and tend to grow sideways or upwards. Their colour varies from green to grey-green or bluish.

In Finland, Colorado spruce deteriorates rapidly through lack of light if planted en masse, but it grows well as individuals in gardens and parks. The blue-grey form known as “silver spruce” is one of the most popular landscape conifers used throughout southern and central Finland. A huge number of special shapes and colour variations have also been developed.