Colorado Spruce, Picea pungens glauca
Etymology: the "fir of the Colorado" was discovered in the Colorado in 1862 by the doctor C. Parry. It is the cultivar ' Glauca Koster ', got in 1885 by Dutch Arie Koster that is the most popular of blue firs today ("glaucous" means "bluish"). The true appellation of " blue fir " should be reserved to Abies procera, or " noble fir ", native to the mountains of Oregon, where it was discovered in 1825 by David Douglas. The dwarf spruce of the Colorado, Picea pungens ' Glauca Globosa ' is fluently called " dwarf blue Fir ". It is the most spread cultivar, and surely one of the best varieties for small gardens and culture in receptacle (photo down). It forms a pretty compact bowl, which evolves in rounded pyramid that can attain 2 m tall in 30 years. The annual medium growth is from 6 to 8 cm. The prickly, tight and short needles, keep a nice blue silvery shade all year through. Colorado Spruce is cultivated since 1937.
Origin : North America, rocky mountains, where it lives between 1 800 and 3 000 m of altitude
Habitat: half-shade, preferably. Soil preferably light and well drained. Colorado Spruce likes the acid soils, fears stagnant humidity and excesses of drought.
Height: 45 m tall in nature, but it exceeds seldom 20 m in culture. The cultivar ' Glauca Koster ' attains 15 m tall.
Shape: conical (of a pyramid). In species at spread form like Picea pungens ' Prostrata ', it is recommended to prune the vertical shoots, to respect the spread, very original outline of these varieties.
Persistent foliage. Needles from 2 to 3 cm, quadrangular, prickly, in "squalid" colour in variety ' Glauca ', disposed in "bottlebrush" on the stem (they encircle it, as a bottle brush).
Fruits: cones form when the tree is 20 years old. Cones with oblong scales are generally covered with resin.
Use: ornamental tree, as well the tree as the dwarf varieties.
Advices of maintenance:
Watch the appearance of the red spiders by hot and dry time!
Give a shower to your blue fir with freshwater every evening of heat wave. As soon as the external temperature exceeds 25 °C, deal as a precautionary measure with a specific acaricide (based on dicofol) in the morning before heat is too intense.
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