Nectaries

Flowering plants attract honey bees and other pollinators as a method of moving pollen within and among flowers to reproduce the plants. To attract the pollinators, plants emit fragrances, display colorful flowers with intricate shapes, and offer tasty and nutritious foods. The foods are carbohydrates from nectar and proteins, fats, vitamins, and minerals from pollen. Nectar is usually secreted by the flowers. Honey bees are directed to the nectary, the nectar-bearing part of the flower, by ultraviolet nectar guides. The nectary is usually located in the center of the flower. However, nectar is secreted by some plants in areas outside of the flowers. Among the plants with extra-floral nectaries is the catalpa tree, which is now in bloom. Today, I watched a Baltimore oriole feeding on nectar in catalpa flowers. Honey bees were flying into the large bell-shaped white catalpa flowers, and they were also working extra-floral nectaries on the large catalpa leaves. The leaves secrete sugary nectar to attract pollinators like the bees in today’s photo. Catalpa trees are members of the trumpet creeper family. After pollination, catalpa produces wind-dispersed seeds that hang in long pods.

Cotton is another flowering plant that secretes large amounts of nectar outside of the flower. After the first day’s bloom, which yields nectar from the blossom, cotton secretes nectar from bracts, leaf-like parts outside of the flower, and from leaves. Other plants have flowers that make it difficult for some pollinators to access the nectary. Honeysuckle flowers have a long bell-shaped flower making it difficult for honey bee tongues to reach the nectar. However, honey bees can access honeysuckle nectar after leaf-cutting bees chew through the side of the flower. Honey bees follow leaf-cutting bees to forage on hosta lilies as well. To access the nectar of alfalfa, honey bees must trip a trigger in the flower which delivers an annoying slap in the bee’s face. The foraging techniques used by honey bees to access the nectar of different plants are learned behaviors.

--Richard

Catalpa in Bloom

The Catalpa is a large, spreading tree with large round, heart-shaped leaves that is often recognized by its long seed pods. The seed pods, over a foot in length, remain on the tree for a long time. The catalpa is in bloom now with large, white flowers with purple or brown stripes. The nectary from which the honey bees collect nectar to produce honey is located both inside the flower and on the underside of the leaves. Pollination by insects is a necessary step in the production of the seeds. The catalpa and the honey bee share a mutually beneficial relationship. The catalpa helps feed the honey bee, and the honey bee helps ensure reproduction of the catalpa. The catalpa is well known throughout the Mid-South as a source of fish bait. Catalpa worms, brightly colored caterpillars that can be found on the leaves of catalpas in the summertime, are collected as highly effective catfish bait.

The catalpa tree is a member of the trumpet creeper family. The trumpet creeper is a vine with large orange flowers that is very attractive to hummingbirds. Many of the plants with deep flowers cannot be worked by honey bees, because their tongues won’t reach the nectar. In these cases, the honey bees rely on leaf cutting bees to make a hole in the base of the flower, exposing the nectar. On this day the catalpa was visited by soldier beetles, solitary bees, carpenter bees, and honey bees. All of the insects appeared to be working the nectary inside the flower.
--Richard