Beloved as a colorful flower annual for shady locations in the garden, impatiens or "bizzy lizzies" come in a wide array of flower colors and leaf variegation. Appreciating consistently moist soil, they quickly wilt in dry or sunny, hot conditions and in subtropical climates use the least amount of irrigation in the cooler months of the dry season. Many varieties readily set seed and cause little seedlings to sprout the next growing season.
While temperate-zone gardeners raise impatiens as summer seasonal annuals, these actually are tropical frost-tender perennials that can persist for years. Some species become sub-shrubs, a term used to describe plants that attain a shrub-like status but do not grow firm, woody stems. Most garden plants belong to the species Impatiens walleriana, native to southeastern Africa. Lots of hybridization occurs by seed companies to expand the array of plants and include series with names like Accent, Deco, Impulse, Novette, Super Elfin, Tempo or Tiara. New Guinea impatiens are complex hybrids that tolerate more intense light and often display variegated or bronze-tinted foliage.
Impatiens belong to the balsam family, Balsaminaceae. This large family only contains two genera: Hydrocera and Impatiens. There are about 850 different species of impatiens, most native to Africa and Southeast Asia.
The flowers of impatiens look like they consist of five petals, but more accurately there are two petals with fused lobes and one petal-like sepal with a spur-like nectar tube. Blossoms rotate themselves 180 degrees as they mature, a phenomenon called resupination. In the flower center is a five-chambered ovary surrounded by five pollen-carrying anthers.
After the flower dies, the insect-pollinated and fertilized ovary swells and ripens into a dry capsule. The capsule ruptures, projecting the seeds far from the mother plant. This explosive mechanism leads to impatiens sometimes being called "touch-me-nots", since a touch or breeze triggers the capsule rupture, sending unwanted seeds to other parts of the landscape. This leads to plants being considered weedy.
While not well-adapted to survive in dry soils or overly hot conditions, impatiens can be challenged by pests and diseases. Any sucking or chewing insect, like aphids or caterpillars, wreak havoc on the succulent leaves and snails can do the same on the tender, succulent stems. Fungal problems like damp rot and mildew also become common since impatiens relish moist soil, high humidity and warm temperature conditions.