The refreshing taste and smell of limes enlivens the senses, enhancing the flavors of seafood, meats, avocados, salads and cold beverages. Limes are the most frost-tender of citrus, growing in U.S. Department of Agriculture plant hardiness zones 9 through 11. However, in colder areas, they grow well as container plants. There are two kinds of limes, Mexican limes (Citrus aurantifolia) and "Tahiti" limes (C. latifolia). Both are self-fertile and seedless "Tahiti" doesn't need pollination. Mexican limes can be pollinated if higher fruit set is desired.
White scentless or faintly fragrant flowers are produced year-round on Mexican limes, with two peak bloom times in late winter and again in mid-summer. "Tahiti" bears purple-tinged flowers mostly in January, but some are produced year-long. Five white petals surround the reproductive flower parts. The female flower parts, the pistil, are in the middle of the flower. The stigma, a round, sticky-tipped structure, is atop the cylindrical style, which leads down to the ovary, where seeds grow. The pistil is surrounded by a ring of stamens, the male flower structures. An anther at the end of each stamen produces pollen. In "Tahiti" limes, anthers are sterile, not producing any pollen. This is not unusual in hybrid plants, and "Tahiti" is a triploid hybrid.
Pollination is the transfer of pollen from anthers to the stigma. When a pollen grain lands on the sticky stigma surface, it grows a pollen tube down the length of the style to the ovary, so the pollen can fertilize one of the ovules to begin seed formation. In citrus, a pulpy fruit surrounds the seeds. In many plants, cross-pollination, or pollen from a completely different plant or variety, is needed for successful seed growth, but that is not the case in limes. Mexican limes are occasionally cross-pollinated for hybridizing purposes, such as the creation of the limequat by crossing kumquat with lime.
When limes grow outdoors, pollination occurs by natural forces such as wind shaking pollen loose and honeybees transferring pollen. When grown indoors, Mexican limes are pollinated by gently shaking the plant or by transferring pollen by hand. Touch a clean small artist's brush or a clean cotton-tipped swab to the pollen-bearing anthers, collecting pollen from several flowers. Then touch the brush or swab to the stigma tip to transfer a load of pollen grains to the sticky surface.
In Mexican limes, also called West Indian or Key limes, fruit formation follows fertilization and it takes five to six months for fruits to mature. Mexican limes have small, intensely aromatic fruits that contain a few too many small seeds. Cross-pollination usually results in more seeds and a 20 percent higher fruit set. In larger "Tahiti" limes, which are also called "Bearss" limes or Persian limes, fruits are seedless due to a process called parthenocarpy, in which the flower fertilizes itself internally and pollination is not needed. "Tahiti" is regarded as strongly parthenocarpic, setting good crops of fruit on its own. If "Tahiti" is hand-pollinated rather than simply allowing limes to develop unaided, fruits usually contain seeds.
- Fruits of Warm Climates: Citrus Aurantifolia Swingle; Julia Morton
- Fruits of Warm Climates: Tahiti Lime; Julia Morton
- University of Florida IFAS Extension: Pollination of Citrus by Honey Bees
- Rodale's All-New Encyclopedia of Organic Gardening; Fern Bradley, Barbara Ellis
- Purdue University Horticulture: Lecture 32 Citrus
- University of Florida IFAS Extension: Growing 'Tahiti' Limes in the Home Landscape
- Zedcor Wholly Owned/PhotoObjects.net/Getty Images