Gardeners often encounter the vibrant orange blooms of the tiger lily and wonder about its true nature. This article aims to clarify whether this beautiful plant is truly invasive or simply spreads aggressively, providing information to help gardeners understand and manage its presence.
Understanding Tiger Lilies
The plant commonly called “tiger lily” is Lilium lancifolium, a herbaceous perennial belonging to the lily family (Liliaceae). Native to East Asia, including China, Japan, and Korea, it has naturalized in many parts of the world, notably eastern North America.
Lilium lancifolium is identifiable by its showy, unscented, bright orange flowers with dark spots resembling a tiger’s skin. Its large, 4 to 6-inch (10 to 15 cm) blossoms typically face downward with recurved petals. The plant grows on upright stems, reaching 2 to 6 feet (60 to 180 cm), with lance-shaped leaves. A key identification feature is the presence of small, dark, pea-sized bulbils that form in the leaf axils.
Distinguish Lilium lancifolium from daylilies (Hemerocallis species), also sometimes called “tiger lily.” While both have showy flowers, daylilies grow from fibrous roots with grassy foliage, unlike true lilies which grow from scaly bulbs with foliage along their stems. Daylilies have upward-facing, trumpet-shaped flowers, and their individual blooms last only one day, unlike the longer-lasting Lilium lancifolium flowers.
Are Tiger Lilies Invasive?
Lilium lancifolium is considered invasive in some regions, especially outside cultivated gardens. An “invasive” species is non-native and causes environmental, economic, or health harm. An “aggressive” plant spreads vigorously in a garden but doesn’t disrupt natural ecosystems. While aggressive in gardens, its invasiveness stems from its ability to escape cultivation and establish dense stands in natural areas.
In natural ecosystems, it outcompetes native flora, forming thick patches that monopolize resources and reduce biodiversity by displacing native plants. It also acts as a symptomless carrier of the lily mosaic virus, which can transmit to and severely damage or kill other lily species, including native ones, with no known cure. Its ability to thrive in various conditions, including disturbed sites like roadsides and abandoned areas, further contributes to its spread and potential for ecological disruption.
How Tiger Lilies Spread
Lilium lancifolium primarily propagates through two mechanisms. The most distinctive method is bulbils: small, dark, pea-sized structures that form in leaf axils. These miniature bulbs detach, drop to the ground, and root into new, genetically identical plants. A single plant can produce numerous bulbils, enabling swift and widespread colonization.
It also has a robust underground bulb system. These bulbs multiply, forming dense clumps and expanding the plant’s footprint. While seed production can occur, it is less common for Lilium lancifolium, especially in its introduced ranges where it is often a sterile triploid.
Managing Tiger Lilies
Managing Lilium lancifolium requires consistent effort due to its vigorous spreading habits. For removal, careful digging is crucial to extract all underground bulbs and any fallen bulbils. Even small fragments left behind can re-sprout, making thorough removal a multi-season endeavor.
To prevent further spread, deadhead spent flowers and promptly remove developing bulbils from leaf axils before they mature and drop. Dispose of removed plant material, including bulbs and bulbils, by bagging and trashing them, not composting, to avoid inadvertent spread. For gardeners seeking a similar aesthetic without the invasive risk, consider planting native lily species such as Canada lily (Lilium canadense), wood lily (Lilium philadelphicum), or Turk’s cap lily (Lilium superbum). These alternatives offer beauty while supporting local ecosystems.