True lilies (such as Asiatic, Oriental, and Trumpet varieties) require specific cutting techniques to remain vigorous and produce robust blooms next year. Understanding when and how far down to cut these plants is essential for promoting long-term health and successful flowering. The process involves two main stages: removing spent flowers and eventually cutting back the foliage for dormancy.
Cutting Back Spent Blooms
Removing spent flowers, known as deadheading, should be done immediately after the petals fade to redirect the plant’s energy. If a faded flower remains, it develops a seed pod, which requires energy better utilized by the underground bulb for next season’s growth.
When deadheading, use clean shears or snap off the faded flower and the short stem directly beneath it. The goal is to remove the flower before it sets seed, leaving the main, leafy stalk completely intact. Leave as much green foliage on the stem as possible, as these leaves actively gather energy for the bulb. Deadheading supports the quality of next year’s display, though it does not encourage new flowers in the current season.
Preparing Lilies for Dormancy
The main stem and foliage of true lilies should not be cut back until the plant enters its dormant phase. This stage typically occurs in late summer or early fall, long after the blooming period has finished. The indicator to watch for is the foliage turning completely yellow or brown.
Once the entire stem has yellowed and become dry, cut it back to a height of four to six inches above the soil line. Cutting the stem back to this height prevents moisture and pathogens from reaching the underground bulb. This short stub also acts as a visible marker, helping you locate the bulb’s position during winter or when planning spring planting.
The Importance of Waiting to Cut Foliage
Waiting until the foliage is fully yellowed before cutting relates directly to the plant’s biological process of energy storage. The green leaves perform photosynthesis, converting sunlight into sugars that are stored as carbohydrates in the underground bulb. This stored energy fuels the following season’s growth and flowering.
If the green foliage is removed prematurely, the plant cannot complete the necessary energy transfer to the bulb. Cutting the green stem interrupts the flow of carbohydrates, resulting in a weakened bulb that produces fewer, smaller flowers, or sometimes no flowers at all the subsequent year. Waiting until the leaves have completely died back ensures the bulb has maximized its energy reserves.