The height of a lily varies widely depending on its genetic makeup. True lilies belong to the genus Lilium, which includes hundreds of species and thousands of cultivated varieties. The mature height potential can range dramatically, from compact plants barely reaching one foot tall to towering giants standing over seven feet high. Understanding this variation is the first step in determining how large a specific lily will become.
Categorizing Lilies by Height
The vast array of Lilium cultivars are often grouped into categories based on their lineage, and these groups also correlate with their typical mature height potential.
Dwarf or Short Lilies
These are compact versions of popular hybrids, such as certain Asiatic varieties, which are specifically bred to remain small. These lilies are ideal for containers or the front of a garden border, typically reaching heights between one and two feet.
Medium Lilies
The largest group is Medium Lilies, which includes the majority of common garden varieties like most Asiatic and Oriental hybrids. Asiatic hybrids are known for their early bloom time and wide color range, generally growing to a height of three to five feet. Oriental hybrids, recognized for their intense fragrance and large blooms, are similarly sized, typically maturing between three and six feet tall.
Tall or Towering Lilies
Tall or Towering Lilies represent the upper limits of the genus’s height potential, often demanding staking due to their vertical growth. This category includes Trumpet lilies, which can routinely reach four to eight feet tall. Orienpet hybrids, a cross between Oriental and Trumpet lilies, are known for their robust stature of four to eight feet. The species Lilium giganteum, sometimes referred to as the Giant Himalayan Lily, is the most extreme example, capable of reaching eight feet or more under optimal conditions.
Factors Influencing Final Size
While the genetic classification provides a range of potential size, the final height a lily achieves is heavily influenced by the environment. Soil quality is a significant variable, as lilies thrive in well-drained, fertile soil that provides adequate nutrients. Poorly drained or wet soils can stunt a lily’s growth, even if the plant is genetically programmed to be tall.
The amount of available sunlight also plays a role in stem elongation and overall plant health. Lilies generally prefer full sun to partial shade. Inadequate light can lead to a phenomenon called etiolation, where the plant produces weaker, leggier stems in an attempt to reach the light. Commercial growers use precise temperature control, specifically the difference between day and night temperatures (DIF), to manage the final height.
Understanding Spread and Growth Habit
It is important to distinguish between a lily’s vertical height and its horizontal spread. Lilies are vertical growers with a narrow footprint; a single, healthy bulb generally produces one main stem with foliage spanning only six to twelve inches across. They do not spread aggressively like groundcover plants but instead grow in a clumping habit.
The horizontal growth is primarily due to the natural multiplication of the bulb over time, not outward rhizomatous spreading. A mature, healthy bulb will produce small offset bulblets at its base, which eventually grow into new, flowering stems. This process, known as offsetting, causes the lily patch to become denser and visually wider over a period of years, forming a cluster of multiple stalks. Gardeners often plant bulbs eight to twelve inches apart to accommodate this natural clumping and ensure proper air circulation.