The crocus is a familiar sight in early spring gardens, its colorful blooms often pushing through the last patches of snow. These flowers emerge from an underground storage structure that provides the energy for their quick appearance. Understanding the appearance of this subterranean part is necessary for successful planting and cultivation.
Crocus Corms Versus True Bulbs
The structure commonly sold as a crocus “bulb” is botanically known as a corm. A true bulb, such as a tulip or onion, stores food reserves in layered, fleshy leaves. Crocus corms, by contrast, are a solid mass of modified stem tissue that stores the plant’s food supply. This solid interior is a key difference from the layered look of a true bulb. The corm functions as a temporary storage battery, which the plant consumes during its growing season.
Detailed Physical Appearance
A crocus corm is generally shaped like a flattened sphere or disc, often wider than it is tall. Most commercially available corms are small, typically ranging from the size of a nickel to a quarter in diameter. The interior flesh is firm and dense, appearing white or cream-colored when cut open.
The corm is protected by a dry, papery outer covering called a tunic. This tunic is usually light to deep reddish-brown and may have a fibrous or netted texture, which helps shield the inner tissue from damage and moisture loss. Visible rings or nodes often encircle the corm, which are remnants of the sheathing leaves from previous years of growth. The presence of these marks indicates where the corm has successfully developed.
Identifying the Top and Bottom
Determining the corm’s correct orientation is necessary for planting, and the structure provides distinct clues. The top, or apex, of the corm is usually slightly pointed or rounded. This area often displays a small, central bud or the scar from the previous year’s flower stem, which is where the new shoot will emerge.
The bottom of the corm is referred to as the basal plate. This area is typically flat and may appear slightly concave. Thin, thread-like roots often emerge directly from the basal plate, or you may see scars where previous roots were attached. The corm must be planted with this basal plate facing down into the soil.