How Sweet It Is

Debby Luquette
Adams County Master Gardener

(9/13) Gardens are great places to hang out. I can spend a lot of time just watching the non-human activity. From a distance, I watch birds hunting in and around the plants, and retreating as I get closer. Insects allow me to get a little closer. Some are shy and stay out of sight; others are so busy that as long as I stay out of their way, they keep working in plain sight. There are the leaf eating and sap sucking pests I’ll work to remove, or encourage my insect predators to remove for me. But among the busiest are the bees, pollinating flowers as they pick up food – nectar and pollen – for themselves and their young.

There’s got to be something about nectar . . . I’ve tasted nectar. Perhaps you’ve sucked it from honeysuckle flowers, too. It’s really sweet, but you know it has to be more than sugar water, right? How could hummingbirds, bees, butterflies, and all those other creatures eating from our flowers get all the nutrition they need from sugar water?

You are familiar with the idea that bees, butterflies, hummingbirds and other animals are responsible for pollination – moving pollen from the male parts of one flower to the female parts of another so seeds can develop. The insect, bird or bat doesn’t move pollen out of kindness; it is really taking nectar, and often pollen, from the flowers to meet its own needs. Since this is a case of two organisms helping each other survive, it is considered a mutual relationship. This might be a sweet story, but there is more to it.

Scientists discovered the components of various nectars, so we now know that nectar is more than a mixture of sugars. All flowers make nectar pretty much the same way. Sugar from photosynthesis is moved to the flowers, and then moved from inside flower cells to the area of the flower near the stigma. The stigma is the female part of the flower that receives pollen. These clever flowers! This forces an insect carrying pollen it picked up on one flower to bump against the stigma of another flower and place pollen where it needs to be before it is rewarded with nectar.

The sugar reward in nectar is only part of the story, though. Flowers vary in the amount of sugar in nectar, depending on which creature is likely to visit it. Visitors with long tongues, such as hummingbirds and butterflies, need a dilute mix that is easy to drink. Insects with shorter tongues, like bees, can handle thicker solutions with more sugar. The sugar concentration of nectar changes after it is released into the flower, too. (Cut? You probably figured out that nectar becomes more concentrated the longer it is exposed to air. And so you realize that flower shape could have some influence on sugar content of nectar. Nectar becomes concentrated more quickly on an open flower, like that of a zinnia, than flowers with long, trumpet shape, like bee balm.)

But sugar isn’t the only chemical found in nectar. There are other chemicals, including amino acids, proteins, and chemicals to prevent it from spoilage by bacteria and other microbes. Some flowers produce nectar with fragrance, meant to attract pollinators. (Cut? Considering the primary role of nectar is to attract pollinators, one has to wonder why there aren’t other insects that visit flowers to drink nectar, and not pollinate the flowers. There are some flowers that spike their nectar with toxic or distasteful chemicals meant to discourage nectar stealing by insects and animals that don’t pollinate the flower. )

Some flowers were shown to change the chemical composition of their nectar when ‘cooperative’ insects visit it. A study recently published mentions that scientists using recordings of bees were able to cause Beach Evening Primrose to increase nectar production in response to the recording. The evening primrose was apparently holding on to its nectar resource until a reliable pollinator appeared.

Nectar is only part of the story, providing lots of energy but not much in the way of nutrition. Pollen, the male part of the plant’s reproductive system, is loaded with proteins, starch, fats, minerals and vitamins. Part of the mutual relationship between flower and pollinator is getting the pollinator to move pollen to the female part of the flower in exchange for a pollen and nectar reward. And pollen is a nutritional powerhouse!

Only female bees collect pollen when visiting flowers. Think of how hairy a bumble bee is. The female bees groom themselves, mixing the pollen collected on their hairs with nectar, and place it in special areas of their legs called pollen baskets. Some bees will carry pollen on their abdomens. The pollen missed during grooming is enough to pollinate the flower.

The pollen mixed with nectar is called ‘bee bread,’ the perfect food for developing bee larvae. Honey bees and bumble bees, which live in colonies, make bread for the whole colony’s use. Female solitary bees put bee bread into compartments they construct in their nests. These could be a hole in the ground, or in a cavity formed in dried plant stems or wood. The female then lays an egg on the bee bread and seals the compartment. The egg hatches into a larva, which eats the bread, forms a pupae (similar to a chrysalis in a butterfly), and the bee will emerge the following year. Solitary bees generally have a one year life cycle.

Life in the garden is much more complex than the beautiful floral displays we grow for our pleasure. I’m urging you to spend time watching all the activity, especially the insect activity, occurring around the flowers because bees are among the animal populations that are dwindling. They are fun to watch, but they are also extremely important for food production. In fact, as important as honey bees are, the wild bees do most of the pollinating work.

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