The delicate, bell-shaped blooms of Lily of the Valley (Convallaria majalis) are a classic sign of spring. This perennial is highly valued for its intense fragrance and ability to thrive as a groundcover in shaded areas. However, its robust, spreading nature can lead to aggressive colonization. Understanding the plant’s underground structure is necessary for successful gardening and managing this vigorous favorite.
They Are Pips, Not True Bulbs
The common term “bulb” is botanically inaccurate for Lily of the Valley’s underground storage organs. A true bulb, like a tulip, is a modified stem surrounded by fleshy scale leaves that stores food. Convallaria majalis relies instead on a horizontal underground stem system known as a rhizome. The rhizome serves as the primary mode of expansion, allowing the plant to form extensive, dense colonies.
The parts sold and planted are known in the horticulture trade as “pips.” Pips are the dormant terminal buds or growing tips that form along these creeping rhizomes. These pips are where the new upright shoots, which eventually produce the leaves and flowers, originate. Recognizing the pip as the growth point helps a gardener understand the plant’s spreading habit and manage its growth.
Detailed Physical Description
The rhizomes are thin, creeping stems, typically white or creamy-colored, that grow horizontally just below the soil surface. They form a tangled, fibrous network that allows the plant to spread rapidly and anchor itself firmly. These underground stems continually send out new growth points, contributing to the plant’s reputation as an aggressive groundcover.
Attached to this network are the pips, which are the distinct buds that give rise to the above-ground foliage. Pips are pointed or spear-like and noticeably thicker than the rhizome, generally measuring between one-quarter and one-half inch in diameter. When dormant, the tips often display unique coloration, frequently showing shades of pink, reddish-brown, or purplish hues.
The entire underground system is secured by a fine, dense root structure extending from the rhizomes. This root mass is highly fibrous and mat-like, forming a thick layer just beneath the soil’s surface. This intertwined mass of creamy rhizomes, colored pips, and dense roots makes separation challenging during division.
Handling Precautions and Toxicity
All parts of the Lily of the Valley plant, including the rhizomes and pips, contain potent compounds requiring careful handling. The plant contains a variety of cardiac glycosides, such as convallatoxin, convallarin, and convallamarin. These natural chemicals are powerful cardiotoxins that can interfere with heart function if ingested.
Because pips are often handled during planting or division, it is recommended to wear gardening gloves to prevent skin irritation. Gardeners should exercise caution when working with any part of the plant, ensuring no material is ingested. After handling the underground parts, thoroughly washing hands and tools is an important preventative measure.
It is necessary to keep the rhizomes, pips, and any other plant material away from small children and household pets. The high concentration of toxins means that even small quantities can cause severe adverse effects. Furthermore, the water used in a vase with cut stems can absorb enough cardiac glycosides to become hazardous if consumed.