Garlic, botanically known as Allium sativum, is a widely cultivated plant that employs two distinct strategies for creating new individuals: asexual (vegetative) and sexual reproduction. The majority of the garlic grown for culinary use relies on cloning, a fast and efficient method that ensures a consistent product. Understanding these different methods illuminates why commercial garlic cultivation has remained largely unchanged for thousands of years, while scientists work to improve the crop’s resilience.
The Standard Method Underground Cloves
The standard and most reliable method for growing garlic is through vegetative propagation using the underground bulb’s individual segments, commonly called cloves. Each clove is a lateral bud that is attached to a basal plate, which is the flattened, stem-like part of the bulb. When a single clove is planted, it develops roots from this basal plate and produces a genetically identical copy of the parent plant, essentially creating a clone.
This asexual process is highly favored by commercial growers and home gardeners because it guarantees the resulting bulb will possess the exact same characteristics as the one it came from, including flavor, size, and storage life. For a new bulb to form, the planted clove requires a period of cold exposure, known as vernalization, typically needing four to six weeks below 40°F (4°C) to trigger the bulb-forming process. Without this cold period, the plant will often produce only a leafy top without the desired segmented bulb underneath. The resulting new bulb matures over a typical seven-to-nine-month growing season and contains a cluster of new cloves, ready to start the cycle again.
Above-Ground Reproduction Aerial Bulbils
While the underground clove is the primary vegetative method, some varieties of garlic also reproduce asexually above ground using small structures called bulbils, sometimes referred to as topsets. These bulbils develop in a cluster at the top of a stiff flower stalk, known as a scape, which emerges from the center of the plant. The scape is most characteristic of hardneck garlic varieties, which are known for their woody central stem, while softneck varieties generally do not produce a scape.
The bulbils are small, miniature bulbs that are clones of the parent plant. If planted, these bulbils will grow, but they are much smaller than a typical clove and usually require two to three years of growth to develop into a full-sized, multi-cloved bulb. In nature, the weight of the bulbils can cause the scape to bend over, allowing the bulbils to fall to the ground and root, a survival strategy sometimes called “walking.” Cultivators often remove the scape before the bulbils mature to redirect the plant’s energy toward developing a larger underground bulb.
The Role of True Seeds in Garlic Biology
True sexual reproduction in garlic is a rare event in modern commercial cultivation and involves the formation of a botanical seed. This process requires successful pollination of the tiny flowers that are produced in the same umbel as the bulbils on the scape. However, the vegetative bulbils aggressively compete for the plant’s resources, often stunting the development of the flowers and preventing them from setting viable seed.
For a true seed to form, the plant must be fertile and the bulbils must often be manually removed to allow the flowers to fully develop and be pollinated by insects. The resulting true seeds are genetically distinct from the parent plant, making them highly valued by researchers and plant breeders. Sexual reproduction is the only way to create new garlic varieties, improve disease resistance, and introduce genetic diversity. Growing garlic from true seed is a multi-year process, often requiring two to three years of growth to produce a harvestable, multi-cloved bulb, compared to just one season from a planted clove.