Pinus lambertiana

The sugar pine, known scientifically as Pinus lambertiana, is a massive conifer. It is the tallest and most massive species within the pine family.

These trees are native to the mountain ranges of the Pacific coast. They grow from Oregon south to Baja California in Mexico. You can find them in the Cascade Range and the Sierra Nevada. They prefer growing in mixed forests rather than alone. In their youth, these trees are shade tolerant. This allows them to grow under the canopy of other trees.

The biology of the sugar pine is quite complex. The needles grow in bundles, or fascicles, of five. These needles are long and have a deciduous sheath. The bark is thick and ranges from brown to purple. This thick bark helps the tree resist forest fires. The tree is also known for its enormous cones. These cones can reach up to 20 inches in length. While the Coulter pine has more massive cones, the sugar pine's cones are very large. When squirrels chew them off, the unripe cones can become dangerous projectiles. The seeds have long wings to help the wind carry them away.

Inside the tree, growth happens through specific biological zones. The shoot apex, or the growing tip, has four distinct zones. First, the apical initials produce all the cells for the shoot apex through cell division. Next, a central mother cell creates the rib meristem. This area is characterized by cell expansion and unusual mitosis, which is the process of cell division. The peripheral tissue zone consists of two layers of cells with high frequency mitosis. Finally, the rib meristem forms a regular arrangement of cells that mature into the pith of the axis. During embryonal development, the embryo changes from a smooth shape to a less symmetric one. This change is caused by the orientation of division planes in the embryo axis.

The sugar pine has a massive genome. In 2016, the PineRefSeq consortium sequenced its 31 gigabase mega-genome. This makes it one of the largest genomes ever assembled. Much of this genome comes from transposable elements. These elements are linked to how the sugar pine evolved. Unlike many other plants, the sugar pine has a stable diploid genome. This genome is expanded by these transposable elements rather than frequent polyploidization. Polyploidization is when an organism has extra sets of chromosomes.

History and human connection are deeply tied to this tree. Naturalist John Muir called the sugar pine the "king of the conifers." The name comes from its sweet resin, or sap. Native Americans used this resin as a sweetener. They also ate the seeds raw or roasted. They even used the seeds to make flour or a spread. The inner bark was also edible. In 1826, David Douglas assigned the scientific name. He named it after the botanist Aylmer Bourke Lambert. During the California Gold Rush, the wood was used heavily for lumber.

The sugar pine faces serious environmental threats today. A fungal pathogen called white pine blister rust is a major problem. This fungus was accidentally introduced from Europe in 1909. It has killed a high proportion of sugar pines, especially in the north. The mountain pine beetle also attacks the trees. These beetles lay eggs inside the tree. This stops the tree from defending itself. It can also cause nutrient deficiencies. Climate change makes these issues worse. Higher temperatures can lower resin levels, which weakens the tree's defenses. Warmer winters also help pests and pathogens survive.

Many groups are working to protect these giants. The U.S. Forest Service develops rust-resistant varieties. They introduce these seedlings back into the wild. The Sugar Pine Foundation was created in 2004. They plant seeds in the Sierra Nevada. These seeds come from trees that are resistant to the blister rust. Their goal is to build a wild population that can survive the fungus. Protecting these trees helps the whole ecosystem. Many animals rely on them for food. For example, black bears eat the seeds in the fall. Yellow pine chipmunks and Steller's jays also gather and store the seeds.