Picea engelmannii (Engelmann Spruce) and
Picea pungens (Colorado Blue Spruce)
Pinaceae (Pine Family)
Montane, subalpine, alpine. Woodlands. Spring.
On dry, well drained or highly exposed sites above 9,000 feet, Engelmann Spruce is usually the dominant tree. It can grow to well over 100 feet tall and four feet in diameter or it can be, at the highest altitudes, only a stunted ten feet tall in what are called "banner trees" and "Krummholz" (see photographs on following pages). At right, the young, fifty foot tall trees are growing in front of a mountain-side of Engelmann Spruce.
Colorado Blue Spruce also often grows in thick stands to over 100 feet tall, but it prefers lower altitudes and moist soils (often in drainages or near streams, as pictured below right).
The two Spruces are often quite difficult to tell apart and in some instances do hybridize Several of their characteristics do help to separate them:
Cone size: Engelmann about 2 inches, Colorado about 3.
Bark: Engelmann more cinnamon with age. Colorado Blue Spruce is gray and furrowed.
Twigs: Engelmann hairy, Colorado smooth.
Trunk: Engelmann trunk is clean between major limbs, Colorado trunk is messy with small twigs.
Leaves: New leaves on both species can be blue-green; the overall blue-green cast that one sees on Colorado Blue Spruce along city streets is usually found only on commercially grown hybrids.
Intermountain Flora states that since there are places "where it is nearly impossible to assign specimens to either [Engelmann or Colorado Blue Spruce] ... it would seem logical to treat these ... as varieties of a single species".
Charles Parry collected Picea engelmannii and Picea pungens on Pikes Peak in 1862; he gave the specific epithet to honor his friend, botanical colleague, and doctor, George Engelmann of St. Louis. (Engelmann was the founding botanist of the Missouri Botanical Garden in St. Louis.)
Engelmann published his description of P. Engelmannii along with Parry's name for it in 1863, but it was not until 1879 that he published a description for and named Picea pungens (Colorado Blue Spruce). Until that time he and other botanists called this tree Abies menziesii, because they thought this was the same tree found along the the Pacific Coast, the giant Sitka Spruce!
Although Engelmann placed Engelmann Spruce in the Picea genus in 1863, at the exact same time it was placed in the Abies genus by Parry. It was, in fact, called Abies engelmannii by other botanists, such as, Porter and Coulter in the first Colorado flora in 1874 and Brandegee in his 1876 Hayden Survey botanical report.
Even though Englelmann assigned Engelmann Spruce to the Picea genus in 1863, he most probably retracted that classification and placed it in the Abies genus, calling it Abies engelmannii, for as noted above, we know that he accepted Abies menziesii as the scientific name for Colorado Blue Spruce and he certainly saw how very similar the two trees are.
In the 1850s and 1860s Elie Carriere re-examined the classification of conifers and it was almost certainly his work that caused Engelmann in 1879 to rename Abies menziesii to Picea pungens and to once again accept the name Picea engelmannii. And Picea engelmannii and Picea pungens have remained the name of these two grand trees ever since.
This convoluted story about the naming of these two trees is not uncommon. As scientific knowledge grows, old assumptions are reexamined and they are verified, modified, or discarded.
"Picea" is derived from the Latin "pix", or "picis", meaning "pitch", and is the classical Latin name for a now unknown Pine.
Curtains of Engelmann Spruce pollen billow into the air from lower branches to ensure pollination of the female flowers at the top of the trees.
At lower elevations (8,000 feet and up), Colorado Blue Spruce enjoy the moisture along streams and lower mountain-sides.
Such intense blue-green is almost always confined to hybridized
Colorado Blue Spruce nursery stock, as in this case.