Nectariferous Plants

a large group of angiosperms producing nectar and pollen that are gathered by bees. Because bees live entirely on nectar and pollen, nectariferous plants are vital to the beekeeping industry. Nectar is produced by glands, or nectaries, which are positioned deep in the flower and resemble flat spots, nodules, grooves, and other forms. Sometimes the nectaries are hidden within specially thickened sepals or petals; less commonly, they are positioned on stems, petioles, stipules, and bracts.

The amount of nectar produced by a flower varies greatly in different species. The tropical orchids of the genus Coryanthes yield up to 30 g; lindens, 0.15-7.46 mg; large-leaved limes, 0.5-11.54 mg; raspberries, 14 mg (on the average); and sweet clover, 0.16 mg. The common honeybee and other insects of the family Apidae process nectar into honey and pollen into bee-bread. Often a single plant provides bees with both nectar and pollen. Certain nectariferous plants, such as poplar, birch, and cherry, also exude resinous substances from which the bees make propolis, or bee glue.

The ability of plants to produce nectar evolved as an adaptation to cross-pollination by insects. To ensure cross-pollination by insects, plants either developed nectar-producing organs or increased their nectar production. Insect cross-pollination is particularly important for such agricultural crops as buckwheat, clover, medic, sweet clover, sainfoin, vetch, beans, and other field crops; sunflower, mustard, radish, rape, and other oil plants; anise, coriander, mint, sage, valerian, and other plants that yield essential oils and spices; cotton, kenaf, and other fiber plants; and many garden crops, including citrus plants, melons, and grapes. The production of nectar and its collection by bees occurs during flowering. The beginning and duration of nectar flow are determined by biological characteristics of the plants and by climatic and geographical factors, such as soil and weather conditions.

In the USSR there are more than 1,000 species of nectariferous plants. However, only about 200 of these species are accessible to and provide enough nectar for bees. A significant number of the plants are agricultural crops. Nectariferous plants are classified according to botanical and economic features, the time of flowering (spring, summer, or fall), the growing site, and other factors.

The most important nectar producers are, among trees and shrubs, lindens (more than 1,000 kg of nectar per hectare of evenly seeded plantings), common maples (more than 1,000 kg), Norway maples (up to 200 kg), willows (up to 150 kg), and Siberian pea trees (about 350 kg); among fruit trees, apples, pears, plums, cherries, and sweet cherries (each yields 20-30 kg); among berry shrubs, currants (50-60 kg), gooseberries (50-60 kg), and raspberries (up to 200 kg); among herbaceous plants, such groat plants as buckwheat (60-90 kg), such oil plants as sunflower (30-40 kg) and white mustard (about 40 kg), such fiber plants as cotton (50-60 kg), such essential oil producers as coriander (200 kg and more), and such fodder plants as sainfoin (90-400 kg), white sweet clover and yellow sweet clover (about 300 kg), the white-pink clover Trifolium albopurpureum (about 125 kg), white clover (up to 100 kg), and sickle alfalfa (about 100 kg); and among plants raised particularly for nectar, phacelia (150-200 kg), vipers bugloss (about 300 kg), and fireweed (300-350 kg).

Other forest plants raised for their nectar include angelica, Siberian angelica, lungwort, evening primrose, goldenrod, ground ivy, Jacob’s ladder, and figwort. Meadow plants cultivated for nectar include larkspur, meadow cranesbill, the cranesbill Geranium caucasicum, sage, and burnet. Some nectar-producing plants can be raised in various places, such as burdock, white dead nettle, alkanet, blue fenugreek, woundwort, motherwort, and dandelion.

By taking the time and duration of flowering into consideration when planting, periods without nectar flow can be avoided in all regions. In addition, the quantity and quality of the honey are improved. The transporting of hives over great distances to regions with flowering nectariferous plants plays a large role in increasing honey harvests.