Canola is a specific cultivar of rapeseed belonging to the Brassica genus, developed through traditional plant breeding methods. It is a variety of Brassica napus or Brassica rapa modified to contain low levels of erucic acid in its oil and low glucosinolates in the meal, distinguishing it from traditional rapeseed oil. This modification led to the name “Canola,” a contraction of “Canadian oil, low acid,” reflecting its Canadian origins and improved nutritional profile. Canola is now a major global oilseed crop, cultivated in vast fields to produce cooking oil and livestock feed.
Overall Plant Structure and Leaves
The mature canola plant is characterized by its upright, highly branched stature, typically reaching a height of three to five feet. The stem is erect and often exhibits a smooth, waxy, blue-green coloration, a feature known as glaucous, which helps the plant conserve water. This robust stem provides the support necessary for the dense canopy of flowers and the eventual heavy load of seed pods.
The leaves are a defining feature, particularly the larger basal leaves that form a loose rosette close to the ground early in the season. These lower leaves are usually stalked and deeply lobed or indented, giving them a resemblance to other members of the mustard or cabbage family. As the plant grows taller and the stem elongates, the leaves higher up the stalk become progressively smaller and less lobed.
Upper stem leaves are often sessile, meaning they lack a stalk, and partially clasp the main stem. The leaves of the most common species, Brassica napus, are characteristically hairless, smooth, and a bluish-green color. This overall vegetative structure provides a large surface area for photosynthesis before the reproductive phase begins.
The Signature Yellow Flowers
The appearance of the inflorescence marks the visual transformation of a canola field. These bright yellow flowers form dense clusters at the top of the plant and along the secondary branches, creating the vibrant yellow carpets seen across agricultural landscapes. The flowers are arranged on an elongated stalk called a raceme, with newer buds found toward the tip.
Each individual flower is relatively small, measuring about a centimeter in diameter. They possess the classic structure of the Brassicaceae family, featuring four petals arranged symmetrically in a cross-like or cruciform shape. The petals are a vivid yellow hue, which is highly effective at attracting the insect pollinators necessary for seed production.
Flowering begins with the opening of the lowest bud on the main stem and continues upward, with the plant simultaneously developing new buds and opening existing ones. This extended flowering period allows the plant to compensate for any early environmental stresses. The brilliant color of the blooms is the plant’s most recognizable stage, signaling the transition into seed development.
Seed Pod Development and Appearance
After successful pollination, the flower petals drop, and the ovary develops into the plant’s fruiting body, known as a silique. These seed pods are slender, elongated capsules, a characteristic shape for the mustard family. Siliques typically range in length from one to four inches (45 to 100 millimeters).
Initially, the pods are a bright green color while the seeds develop and accumulate oil. Each silique contains between 15 and 30 seeds arranged in two rows, separated by a thin membrane. As the seeds mature, the pod gradually changes color, transitioning from green to pale yellow, and eventually drying to a tan or light brown color.
The pods begin to form on the lower part of the main stem first, progressing upward as flowering continues. At full maturity, the pods become brittle and prone to shattering, which is the natural mechanism for seed dispersal. The small, spherical seeds inside are typically brownish-black, though some varieties produce yellow seeds.