The term “lily” is widely used, causing confusion about whether the plant should be kept indoors or outdoors. This common name is applied to many different species from various plant families, each having distinct environmental requirements. The answer depends entirely on the specific plant species. Understanding the actual botanical identity of a plant labeled as a “lily” is the first step toward successful cultivation.
Understanding the Botanical Classification of “Lilies”
The scientific classification reveals the core difference between plants sharing the common name “lily.” Only plants belonging to the genus Lilium are considered “True Lilies.” These include Asiatic, Oriental, and Trumpet hybrids, which grow from scaly bulbs and are overwhelmingly cold-hardy outdoor garden plants native to temperate regions.
The vast majority of plants commonly grown indoors and called lilies are members of completely different genera. For example, the popular Peace Lily is Spathiphyllum, and the Calla Lily is Zantedeschia. These “lily imposters” share a similar flower form but belong to the Araceae plant family, not the true lily family, Liliaceae. This distinction explains why their ideal growing conditions differ significantly from true garden lilies.
Essential Care for Outdoor Garden Lilies (True Lilium Species)
True lilies (Lilium species) require a period of cold dormancy and are cultivated outdoors in garden beds. They thrive when planted in rich, well-draining soil that is slightly acidic to neutral in pH. Proper drainage is essential, as the fleshy bulbs will rot quickly in saturated ground.
Most Lilium varieties perform best when receiving at least six hours of direct sunlight daily; some benefit from afternoon shade in hot climates. The bulbs should be planted four to six inches deep, which helps keep the bulb and roots cool and moist. Consistent moisture is necessary during the active growing season, but watering should be reduced after blooming when the foliage begins to yellow.
The plant needs to store energy for the following year’s bloom, so the foliage must be allowed to die back naturally before being trimmed. In colder zones, a layer of mulch applied in late fall protects the bulbs from harsh winter temperature fluctuations. After several years, a clump of lilies may benefit from division and replanting to maintain vigor.
Cultivating Common Indoor “Lilies”
The most common indoor “lily” is the Peace Lily (Spathiphyllum), prized for its tolerance of lower light conditions. This plant prefers bright, indirect light but can survive in shadier spots, though flowering may be reduced. Peace Lilies originate from tropical rainforests, requiring consistently moist soil and high humidity levels.
Allowing the top inch of potting mix to dry slightly between waterings is a good practice, but the plant should never be left to wilt. Calla Lilies (Zantedeschia) are also grown indoors, often from dormant rhizomes. Unlike Peace Lilies, colored Calla Lilies require significantly brighter light, often benefiting from a few hours of gentle direct sun.
Calla Lilies need a rich, moist potting mix during their active growth and blooming phase. They typically enter a period of winter dormancy where the leaves die back. During this dormant phase, watering must be severely restricted, and the rhizomes should be kept in a cool, dark location to prepare for the next season.
Toxicity and Safety Considerations
The various plants commonly labeled as lilies have dramatically different toxicity profiles, which is a concern for pet owners. True lilies (Lilium species) are profoundly toxic to cats. Ingestion of any part of the plant, including the pollen, can lead to acute kidney failure and death. Because of this severe risk, true lilies should never be brought into a home with cats.
In contrast, common indoor “lilies” like Peace Lilies (Spathiphyllum) and Calla Lilies (Zantedeschia) contain insoluble calcium oxalate crystals. When chewed, these crystals cause immediate, intense irritation, pain, and swelling of the mouth and throat. While this toxicity is less severe than the kidney failure caused by Lilium species, it results in symptoms like excessive drooling, vomiting, and difficulty swallowing.
For any household with pets or small children, it is prudent to research the specific plant’s scientific name. Placing even mildly toxic plants out of reach is advisable, and any suspected ingestion of a true Lilium by a cat warrants immediate veterinary attention.