Point Imperial, Grand Canyon North Rim
Anyone who’s been to the Grand Canyon North Rim can tell you that hiking can be hard on the lungs given the altitude of just under 8,300 feet. And that’s just for starters. Beautiful Point Imperial, the highest of the North Rim overlooks, tops out at almost 9,000. My daughter recently observed (while gingerly approaching the edge) that she felt like she was slogging through a pool of molasses. That prompted me to wonder; how do high altitude plants grow under such challenging conditions? I set out to find the answer.
HOW THEY DO IT
The first thing I discovered was that high altitude plants are not like their lowland cousins. In order to survive, they have made some structural adaptations. These include irreversible, highly evolved physical responses to high-altitude environments not seen in low altitude plants. And this mix of strategies, while particular to each species, often benefits the surrounding plant and animal communities as well.
The creamy flowers of cliffrose, blooming at 8,800 feet
TAKING A BREATHER
As chests heaving, we made our way to Point Imperial, I paused to reflect on the many plants that bordered the trail. How were these species thriving? For starters, air pressure is much thinner at higher elevations. In humans, this makes it hard for veins to pump oxygen throughout the body.
It turns out that at upper elevations, reduced pressure makes it harder for plants to pump water from soil to stem, too. But unlike humans, high altitude plants have come up with a solution. Rather than struggle to draw water and nutrients through normal-sized vascular systems, they have evolved smaller sized pathways. These ‘custom’ vascular pathways allow them to channel fluids more quickly through a tighter area.
Firecracker penstemon, a desert native, growing at 8,800 feet
HIGH ALTITUDE PLANTS LIKE THEIR SPACE
Partly due to these reduced hydraulic systems, trees and plants at high elevations tend to be smaller (to conserve energy) and to grow more slowly. They also are more likely to be spaced further apart. Western juniper, for instance, prefers to make its home on dry, rocky sites where there is less competition from larger species. And in exposed areas, it often assumes a stunted form, growing low to the ground.
Indeed, Western juniper is sometimes described as looking like ‘polka-dots on the hillside’ for this very reason.
Juniper growing on the slopes of the Grand Canyon
SOME OF THE OLDEST PLANTS IN EXISTENCE
Slower growth has the added benefit of longevity. In fact, some of the oldest trees in existence grow at high altitude. This includes the bristlecone pine, which is said to be the oldest known living tree, with some specimens believed to be over 4,000 years old.
An old bristlecone pine
PUTTING DOWN ROOTS
But I’m particularly impressed by the resilience of the Utah juniper, which can survive even the harshest of conditions. It can grow a 40 foot-long tap root that extends straight down through rocks and crevices. And its lateral roots can travel as far as 100 feet away. This strategy ensures that parts of the tree survive even if the tree itself is knocked down. In extreme cases, Utah juniper can even concentrate nutrients in just a few branches, keeping the main tree alive while the rest of the body shuts down.
Crooked remains of a Utah juniper – is it just conserving energy?
There’s no mistaking this shaggy, twisted shrub that grows high on dry rocky slopes in the Western United States. A member of the rose family, cliffrose has fragrant, creamy blooms that appear from spring to fall and provide important forage food for deer, cattle and sheep, especially during the winter. Moreover, its highly absorbent bark and evergreen leaves enable the plant to retain moisture.
Gnarled branches of cliffrose
But here’s the coolest thing about cliffrose; its mature seed has a long-tailed hair that attaches to the end of it. When the wind disperses the seeds, the hairs act like tiny parachutes and once the seed lands on the ground, the hair acts like a drill, rotating with the wind to drive the seed into the rocky soil.
A SILVER LINING
Finally, who can resist the allure of gray and silver foliage? These plants employ an altogether different coping strategy. Gray and silver-leaved plants have tiny white hairs covering the leaf surface. The hairs reflect solar radiation, cooling the plant tissues and trapping moisture, which slows evaporation. This is especially important given the low moisture levels of the higher elevations.
Silver-leaved Winterfat, a species of flowering plant in the amaranth family
Gray-green Big Sagebrush growing on Point Imperial
One has only to look at the sun reflecting off their brilliant leaves to see these plants’ strategy at work.
These are just a few of the many fascinating high altitude plants that populate the upper reaches of the Grand Canyon. For more information on plant and tree life, as well as great hikes to see them, click here for the National Park Service’s Official Site. We stayed at the Grand Canyon Lodge, a spectacular property run by the Park Service, located on the lip of the North Rim.