Shallots are an aggregate bulb, a member of the Allium family distinct from the common onion due to their unique growth pattern. Unlike onions, which typically form a single, large bulb, a single planted shallot will multiply into a cluster of new bulbs. This multiplication makes shallots a highly rewarding crop. The number of bulbs produced from one planted clove is influenced by both genetics and growing conditions.
The Biology of Shallot Multiplication
The shallot (Allium cepa var. aggregatum) is classified as a multiplier onion, meaning its primary reproduction is vegetative. When a single shallot clove, or “set,” is planted, it acts as a mother bulb that begins to divide asexually underground. It initiates the development of several offsets, or daughter bulbs, around its base.
These daughter bulbs form a tight, aggregate cluster, similar to garlic. The division process originates from the basal plate of the planted clove, leading to the formation of multiple vegetative shoots. Each shoot matures into a new, distinct shallot bulb, which is the biological mechanism responsible for the high yield.
Standard Yield Expectations and Influencing Factors
A single shallot clove, or set, yields a cluster of four to twelve new bulbs at harvest, though this range is variable. The final number and size of the bulbs are affected by environmental and genetic factors. The cultivar chosen plays a large role; French Grey shallots often produce fewer, larger bulbs compared to Dutch varieties that may produce a greater number of smaller bulbs.
Climate is a primary influence, as shallots are sensitive to day length and temperature, which trigger the bulbing process. Most shallot varieties require long days to begin forming their bulbs, and insufficient light or heat can delay bulbing and reduce the overall cluster size. Soil quality and consistent moisture are also factors that determine the final yield. Fertile, well-draining soil encourages robust root growth, while inconsistent watering can cause growth checks that limit bulb development.
The nutrient balance in the soil influences the quantity versus the size of the bulbs. High levels of nitrogen promote lush top growth and more multiplication, potentially leading to a greater number of smaller bulbs. Conversely, wider spacing and balanced fertilization with less nitrogen encourage the plant to form fewer, significantly larger individual bulbs. The number of bulbs a single clove produces is determined by the interaction between the plant’s genetics and its growing environment.
Optimizing Planting for Maximum Harvest
To encourage the shallot plant to reach its maximum yield potential, the gardener must optimize the planting technique. Before planting, the aggregate bulb must be separated into individual cloves. Planting the entire cluster without separation results in overcrowding, which restricts the space available for new bulbs to form and expand.
Each clove should be planted root-side down and pointed-tip up, with the tip barely visible above the soil surface. Proper spacing is important for a successful harvest. Planting individual cloves approximately six to eight inches apart allows ample room for the aggregate cluster to form without competing for space and nutrients. This wider spacing supports the expansion of the cluster, leading to a higher number of well-formed, medium-to-large bulbs.
Harvesting and Curing for Storage
The final stage of the shallot growing cycle is timed based on the visual cues of the foliage, which signals that the bulbs have matured underground. Shallots are ready to be lifted when the green tops begin to yellow, wither, and fall over, typically in mid to late summer. This dieback indicates that the plant has finished its bulbing process.
The bulbs must be gently lifted from the soil, taking care not to damage the papery outer skin, which protects the bulb during storage. Once lifted, the shallots require a curing process to prepare them for long-term storage. Curing involves spreading the entire clusters in a single layer in a warm, dry, and well-ventilated area, away from direct sunlight, for a period of one to four weeks. This drying process allows the necks of the bulbs to seal and the outer skins to become papery, preventing moisture loss and inhibiting the growth of mold or bacteria during storage.