Picea engelmannii (Engelmann Spruce)
Pinaceae (Pine Family)
At the upper limits of tree growth (10,500-11,500 feet), Picea engelmanni often grows in almost pure stands. It thrives on the high, dry, rocky, ultra-violet-ray-saturated conditions. Even at tree-line (11,500 feet) mature giants can be four feet in diameter, but much shorter, perhaps 60 feet tall, than other members of their species that grow at 10,000 feet.
At the very limits of tree growth (about 11, 600 feet) on exposed, wind-swept tundra, Picea engelmannii still clings as Krummholtz: "crooked woods". Limbs are sheared off on the windward side forming 10 foot tall banner trees or it is compressed into low shrub-like trees only a few feet tall.