The Calla Lily (Zantedeschia) is a popular perennial grown for its distinctive, trumpet-shaped flowers. This plant requires specific pruning to maintain its appearance and ensure vigorous growth in subsequent seasons. The Calla Lily benefits from two distinct types of cutting back: the removal of individual spent flowers and the seasonal reduction of its entire foliage. Understanding the correct timing and technique for each is important for the plant’s long-term health and ability to bloom year after year.
Pruning Spent Blooms
The first type of cutting back involves deadheading, which is the removal of the flower stalk immediately after the bloom has faded. Calla Lily flowers, or spathes, typically roll up and turn green or brown once finished. Allowing the plant to develop a seed head diverts energy away from the rhizome needed for future growth and flowering. Removing the spent bloom redirects that energy back into the root structure, promoting a healthier plant.
To deadhead effectively, use clean, sharp pruning shears or a knife to make a cut near the base of the flower stalk. It is best to follow the stem all the way down to where it emerges from the main clump of leaves, cutting it off as close to the soil line as possible. This technique prevents leaving unsightly, hollow stubs that can collect water and potentially lead to rot or disease. Regular deadheading throughout the active growing season ensures that the plant focuses its resources on developing a robust rhizome rather than producing seeds.
Seasonal Cut-Back of Foliage
The most substantial cutting back occurs at the end of the growing season as the plant prepares for dormancy. This seasonal pruning should not be rushed, as the timing is determined by the plant’s physiological signals. The leaves must be allowed to yellow, then brown, before they are removed, a process known as dying back. This change indicates that the plant is reabsorbing nutrients and storing them back into the rhizome.
Cutting the green foliage prematurely would interrupt this natural process, significantly weakening the rhizome and reducing the plant’s ability to produce flowers the following year. Gardeners must wait until the leaves have completely collapsed or turned entirely yellow and dry, ensuring the rhizome has accumulated maximum energy reserves. Once the foliage is fully spent, it can be cut back to just one to two inches above the soil line. This leaves a small stub that clearly marks the plant’s location without providing a pathway for pests or disease.
In mild climates, particularly for the hardy white Calla Lily (Zantedeschia aethiopica), the foliage may remain semi-evergreen and not require a hard cut-back. However, the more common colored varieties usually require dormancy, especially when grown in cooler regions. Observing the natural dieback of the leaves is the most reliable indicator for when to perform the seasonal cut, typically occurring in the late fall or after the first light frost. This careful timing ensures that the rhizome survives the winter and resumes growth in the spring.
Post-Pruning Care and Winter Preparation
For Calla Lilies grown in warm regions (USDA Hardiness Zones 8 to 10), the rhizomes can generally remain in the ground. In these areas, the best practice involves stopping all watering and adding a generous layer of mulch, such as straw or shredded bark, over the area to insulate the rhizomes from temperature fluctuations. This action protects the underground structure while allowing the plant to enter its dry, dormant phase.
Conversely, in colder climates (Zones 7 and below), the rhizomes will not survive a hard freeze and must be lifted and stored indoors. Carefully dig up the rhizomes, gently brushing off any excess soil without washing them, which could encourage rot. The rhizomes must then be cured by allowing them to dry in a warm, well-ventilated area, ideally between 60°F and 70°F, for about four to seven days.
After curing, the rhizomes develop a tougher outer layer that helps them resist disease during storage. They should then be placed in a ventilated container, such as a paper bag or a cardboard box, and covered with a dry medium like peat moss or vermiculite. The stored rhizomes must be kept in a cool, dry, and dark location, typically around 50°F, until the danger of frost has passed in the spring. This storage process protects the plant’s energy reserves and ensures a strong return to the garden when warmer weather arrives.