The Ponderosa pine (Pinus ponderosa) is a monster tree easily recognizable in the natural vista. This evergreen tree may get up to 165 feet (50 m.) tall and has a soaring straight trunk topped by a relatively small crown. Ponderosa pine information must mention their economic importance as a wood source, but stands still remain of these fast growing giants of the forest. Planting one in the home landscape will eventually add dimension to your yard and provide generations of fragrance and evergreen beauty.
I. Appearance and Characteristics
Pinus ponderosa, commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine, is a very large pine tree species of variable habitat native to mountainous regions of western North America. It is the most widely distributed pine species in North America.
Pinus ponderosa grows in various erect forms from British Columbia southward and eastward through 16 western U.S. states and has been introduced in temperate regions of Europe and in New Zealand. It was first documented in modern science in 1826 in eastern Washington near present-day Spokane (of which it is the official city tree). On that occasion, David Douglas misidentified it as Pinus resinosa (red pine). In 1829, Douglas concluded that he had a new pine among his specimens and coined the name Pinus ponderosa for its heavy wood. In 1836, it was formally named and described by Charles Lawson, a Scottish nurseryman. It was adopted as the official state tree of Montana in 1949.
Pinus ponderosa is a large coniferous pine (evergreen) tree. The bark helps distinguish it from other species. Mature to overmature individuals have yellow to orange-red bark in broad to very broad plates with black crevices. Younger trees have blackish-brown bark, referred to as “blackjacks” by early loggers.
Ponderosa pine’s five subspecies, as classified by some botanists, can be identified by their characteristically bright-green needles (contrasting with blue-green needles that distinguish Jeffrey pine). The Pacific subspecies has the longest—7+3⁄4 inches (19.8 centimetres)—and most flexible needles in plume-like fascicles of three. The Columbia ponderosa pine has long—4+3⁄4–8 in (12–20.5 cm)—and relatively flexible needles in fascicles of three.
The Rocky Mountains subspecies has shorter—3+1⁄2–5+3⁄4 in (9.2–14.4 cm)—and stout needles growing in scopulate (bushy, tuft-like) fascicles of two or three. The southwestern subspecies has 4+1⁄2–7+3⁄4 in (11.2–19.8 cm), stout needles in fascicles of three (averaging 2+3⁄4–3+1⁄2 in or 68.5–89 millimeters).
The central High Plains subspecies is characterized by the fewest needles (1.4 per whorl, on average); stout, upright branches at narrow angles from the trunk; and long green needles—5+3⁄4–7 in (14.8–17.9 cm)—extending farthest along the branch, resembling a fox tail. Needles are widest, stoutest, and fewest (averaging 2+1⁄4–2+3⁄4 in or 56–71 mm) for the species.
The egg-shaped cones, which are often found in great number under trees, are 3–5 in (8–13 cm) long. They are purple when first chewed off by squirrels, but become more brown and spherical as they dry. Each scale has a sharp point.
Sources differ on the scent of P. ponderosa. Some state that the bark smells of turpentine, which could reflect the dominance of terpenes (alpha- and beta-pinenes, as well as delta-3-carene). Others state that it has no distinctive scent, while still others state that the bark smells like vanilla if sampled from a furrow. Sources agree that the Jeffrey pine is more strongly scented than the ponderosa pine. When carved into, pitch-filled stumps emit a scent of fresh pitch.
Pinus ponderosa is classed as a “wilding pine” and spreads as an invasive species throughout the high country of New Zealand, where it is beginning to take over, causing the native species of plants not to be able to grow in those locations. It is also considered a “weed” in parts of Australia.
II. Types of Ponderosa Pine
There are two recognized varieties of the ponderosa pine, Pinus ponderosa var. ponderosa (Pacific ponderosa pine) and Ponderosa pine var. scopulorum (Rocky Mountain ponderosa pine). Most suitable for most home gardens, however, are the dwarf varieties that come in different forms, sizes, and growth rates. These include:
- P. ponderosa ‘Pondy’: A dwarf ponderosa pine with a globose form with needles that are a bit smaller than those of the species. It will grow to about five feet after ten years of growth.
- P. ponderosa ‘The Sphinx’: A pyramidal, dwarf selection of ponderosa pine with tight, uniform branching and long needles. It is slow-growing, reaching a size of 3 feet in height and width after ten years. USDA Zone 5-8
- P. ponderosa ‘Warm Valley’: This dwarf variety originated as a witch’s broom. It has a globose growth habit and grows very slowly, only 1 to 3 inches per year, to a size of 4 feet tall to 3.5 feet wide.
III. How to Grow and Care
Sunlight
This tree needs full sun to thrive; it does not tolerate shade.
Temperature and Humidity
Ponderosa pine is a very cold-hardy evergreen tree that performs best in cool, dry conditions and does poorly in humid climates. The areas where the tree grows naturally in USDA Zones 3 to 7 are often mountainous and just because you are in the hardiness range of the tree does not mean that the climate conditions in your area are suitable.
Watering
An established ponderosa pine has great drought tolerance but a young tree needs extra watering. Ponderosa pines are notorious for their root ball drying out, which happens in just one day depending on weather conditions. Always check the actual water needs before watering and water the tree lightly but frequently. A tree with a caliper of less than 2 inches needs to be watered daily for the first two weeks, 1 to 2 gallons per inch of trunk diameter.
After the first week and during the first two months, give the tree 2 to 4 gallons per inch of trunk diameter every other day. After that, water the tree weekly until it is fully established, which may take two growing seasons or more.
Soil
The ideal soil for ponderosa pine is a mix of gravel, sand, and loam with a pH between 6.0 and 7.0 and good drainage. However, as long as the soil has a slightly acidic to neutral pH and it’s not soaking wet, ponderosa pine will grow. This species is rather forgiving in terms of soil conditions, more than other pines.
Fertilizing
There is no need to fertilize an established ponderosa tree unless the soil is lacking a specific nutrient, a fact that only a detailed soil test can reveal. To boost the overall health of a young tree, amend the soil beyond the dripline of the tree with compost and widen the area that you water accordingly. Alternatively, feed the young tree a slow-release evergreen-specific fertilizer in mid spring in the first two years.
Pruning
The main reason to prune a ponderosa pine is to remove dead or broken branches or growth that is getting too close to a structure or a passageway. Pruning should be done in late winter or early spring while the tree is dormant. Cut the branch all the way back to the branch collar (the spot where the branch is attached to the trunk or a larger branch) and never remove more than 25 percent of the tree in any given year.
Propagation
Ponderosa pine is difficult to propagate from cuttings; it is usually propagated from seed. However, obtaining suitable seeds is difficult for home gardeners, as the most viable seeds come from trees that are 60 to 160 years old.2 The seeds from cultivars (the types that most home gardeners will likely choose due to the smaller tree size) won’t produce plants that are true to the parent. The long time that it takes to grow a ponderosa pine is another reason why propagating your own ponderosa pine is not recommended.
Potting and Repotting
Despite their small size and slow growth rate, even a dwarf ponderosa pine is not a good choice for container growing. The tree has a deep tap root and a widespread root system that will be too confined in a pot.
Overwintering
Ponderosa tree is well-equipped to withstand sub zero winters and do not require any winter protection.
Pests and Diseases
Ponderosa pine can be affected by many different insect pests, not all of them serious. Infestations with pine beetles, Western pine beetles, and bark beetles cause tree death. The tree is also prone to parasites, especially dwarf mistletoe, root diseases, rusts, trunk decays, and needle and twig blights.
III. Uses and Benefits
- Ornamental uses
Cultivated as a bonsai, ponderosas are prized for their rough, flaky bark, contorted trunks, flexible limbs, and dramatic deadwood. Collected specimens can be wildly sculpted by their environment, resulting in beautiful twisted trunks, limbs and deadwood. In the mountains they can be found growing in pockets in the rock, stunting their growth. The main challenge for this species in bonsai cultivation is the natural long length of its needles, which takes years of training and care to reduce.
This species is grown as an ornamental plant in parks and large gardens.
- In nuclear testing
During Operation Upshot–Knothole in 1953, a nuclear test was performed in which 145 ponderosa pines were cut down by the United States Forest Service and transported to Area 5 of the Nevada Test Site, where they were planted into the ground and exposed to a nuclear blast to see what the blast wave would do to a forest. The trees were partially burned and blown over.
- Uses in Native Americans
Native Americans consumed the seeds and sweet inner bark. They chewed the dried pitch, which was also used as a salve. They used the limbs and branches as firewood and building material, and the trunks were carved into canoes. The needles and roots were made into baskets. The needles were also boiled into a solution to treat coughs and fevers.
In the 19th and 20th centuries, old-growth trees were widely used by settlers as lumber, including for railroads. Younger trees are of poor quality for lumber due to the tendency to warp.
