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A Hefty Pine

This is a majestic, long-lived pine, growing more than 200 feet tall in the wild (photo). With age it sheds its lower branches, revealing a straight trunk and crocodile bark made of large plates with broad cracks between them. Like redwoods, it is rarely harmed by brush fires.

Ponderosa pine grows in a larger native range than any pine of North America--from coastal California across the Sierra Nevada Mountains out to the eastern flanks of the Rocky Mountains, into the arid hills of southeastern Arizona and on to Texas and Mexico (map) where it tends to grow in mountains with some rainfall, on well-drained soils, and even on rock if it can find cracks for its roots.

It has adapted to the different climates of the American West partly by cleaving into two subspecies, the Rocky Mountain Ponderosa pine (var. scopulorum), which has short needles grouped in twos, and the Arizona Ponderosa pine (var arizonica, which has slender needles grouped in fives, though the number can vary. The Arizona subspecies is half the height of the tallest Ponderosas in the Rockies and Sierras. As usual, the botanists are re-thinking things and arizonica may be declared a separate species some day.

The name Pinus ponderosa points to the wood of the tree--unusually hard and dense for a pine. The adjective “ponderous” (as in “large” or “weighty”) descends from the same Latin word as ponderosa. Most pines have softer wood. In fact, they’re called softwoods in contrast to, say, oaks and birches, which are called hardwoods. Drive a nail into dry white oak and dry white pine and you’ll feel the difference.

For some reason, there are no unusual forms of this pine in the nursery trade. No dwarf or weeping forms, no forms with yellow or striped needles. At least I have not found them. (If you know otherwise, please post sources and names at YourGardenShow.com.) Nonetheless, it’s a useful tree in its range and even on small properties will stay in scale for several decades. It’s rarely grown on Christmas tree farms because shearing the needles may not produce a uniform tree and because most of the evergreen species grown as Christmas trees do best in northern climates with more rainfall than the Ponderosa pine tolerates.

The wide range of the Ponderosa pine makes it a valuable plant for the research of the USA-NPN, the National Phenology Network, which has placed it among a short list of “calibration plant species.” Volunteers (many are amateurs) observe these species and record the dates of annual events in their life cycles--flowering, buds opening and more, depending on the species. For the Ponderosa pine the events include new needles emerging, pollen release, and ripe seed cones.

Phenology research has many uses. One is monitoring climate. If pollen appears earlier this year than it did ten years ago, the difference is one measure of global warming. We know the trees aren’t changing. They are responding to the cues from the environment that they have evolved to rely on (warming temperatures in springtime, for example).

Gardeners will use the science too, timing plantings and harvests by the cycles of local calibration species as the data becomes better known and science replaces lore. Our forebears did their own phenology. There’s an old saying in the northeastern U.S. that you plant corn when oak leaves are the size of a squirrel’s ear.

By Mark Kane - the Groundskeeper, YourGardenShow.com

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