Tiger lilies are one of those exotic plants that are members of the lily family. These lilies are summer flowering bulbs that are perennial and so regrow each year. So why may growing them be a bad idea? Well it seems that they are prone to viruses and they tend to spread rather aggressively which can be a problem. To learn more read this article by David Beaulieu which I found on the About.com website.
It’s important to be clear on just what exactly constitutes the “tiger lilies” discussed in this article, because the same common name has been commandeered for totally different plants. The facts below pertain to what plant taxonomists have classified as?Lilium lancifolium?(alternate botanical name,?Lilium tigrinum). The genus name indicates it is a?true lily, not a daylily such as Stella de Oro.
Botanically speaking, these are herbaceous perennials that grow from a bulb. Gardeners generally plant the bulbs in spring. They are summer-flowering bulb plants, unlike daffodils, tulips, etc., which are spring-flowering bulb plants. Note that the word, “bulb” is sometimes used loosely to include related underground plant structures (namely,?corms, rhizomes and tubers). Dahlias and cannas are two of the other popular summer-flowering bulbs.
The nodding, 4-inch flowers bloom in late July in my zone-5 garden. Orange is the classic color for this plant, although it does come in other flower colors (yellow, red). At bloom time, this tall, skinny, unbranched plant stands 5 feet tall. The petals (or, technically, “tepals”) of the highly interesting flowers are recurved (that is, they curve backwards; sometimes the term, “reflexed” is used to describe the same phenomenon) and?speckled with brown spots. Because of this recurving (as well as the dark spots), they are reminiscent of the blooms of Turk’s cap lily (Lilium superbum).
Some of the plants’ reproductive parts (namely, a long style and 6 long stamens) are displayed prominently and shamelessly at the bottom of the flower.
Ten or more flowers per flower stalk is typical. Unhappily, the blooms are not fragrant, as they are on?Stargazer?and?Easter lilies.?The sword shape of the leaves gives the plants their specific-epithet name (lancifolium means “lance-leafed” in Latin).
As spectacular as the flowers are, the bulbils are perhaps even more distinctive. The bulbils are black, berry-like structures housed in the leaf axils (see my picture). To propagate these perennials, some people harvest and plant these bulbils.?But plants will spread over time, on their own, to form larger clumps. If you wish to suppress spreading, removed the bulbils and dispose of them.
See more at About.com