They are perhaps Earth’s most unsung heroes: the bees, butterflies, wasps, flies, and other organisms that maintain balanced ecosystems and thus the health of our food supply through pollination. Native insects, in fact, play a crucial role in pollinating and fertilizing up to 75 percent of plant species on earth, and up to a third of our staple food crops rely upon insects alone to disperse their pollen and fertilize their fruits. Imagine a world without coffee, chocolate, apples, and many other foods that are part of our daily lives. That world likely becomes reality without pollinators.
What, exactly, is pollination? What are the Earth’s key pollinators? And, perhaps most importantly, how can you support their work by creating pollinator-friendly gardens?
What is Pollination?
Pollination is an ecosystem process that has evolved over millions of years to benefit both flowering plants and pollinators. Specifically, it is the event wherein pollen moves from one flower to another and reaches the receptive stigmatic surface of a pistil, thereby producing fertile seeds.
Plants are pollinated by different methods depending upon their flower types. While pollen transfer for self-pollinated plants may or may not involve external factors, cross-pollination always requires outside agents (or vectors) such as insects, birds, or wind to facilitate pollen movement between plants. Without these vectors carrying pollen from one flower to another, often unintentionally, cross-pollination cannot take place, and subsequent fruit and seed production will not occur.
Know your pollinators
Animals or insects that transfer pollen from plant to plant are called “pollinators.” Pollinators visit flowers for many reasons, including food and shelter. Although some plant species rely on wind or water to transfer pollen from one flower to the next, the vast majority—almost 90 percent—of all plant species need the help of animals to accomplish this task. Of the approximately 200,000 different species of animals around the world that act as pollinators, the vast majority are invertebrates, including bees, butterflies, wasps, and flies.
Among pollinators, bees are the superstars—they are the only group of insects that actively collect pollen and, in the process, transfer large amounts of pollen from flower to flower. Bees also exhibit a behavior called floral constancy, which means that they visit flowers of one species repeatedly over a period of time. North America alone boasts more than 5,000 species of native bees, 90 percent of which lead solitary lives. The remaining 10 percent, social bees, live in colonies and share the work of preparing and provisioning the same nest. Whether solitary or social, many species of bees pollinate effectively, with the European honey bee, the bumble bee, and the sweat bee among the most prolific. Each, however, has different habits and prefers different crops:
European Honey Bees: Introduced to North America in the late 1600s, these social bees can forage up to three miles from their hive in search of nectar and pollen and are thus highly effective pollinators. Honey bees tend not to forage during cool and wet weather, but are excellent pollinators of sunflowers, cucurbits (pumpkin, zucchini, cucumber, and watermelon), and many brassicas (broccoli, cauliflower, cabbage, rutabaga, and turnip).
Bumble Bees: These social insects live for only a single season but make the most of their brief lifespan. Very efficient pollinators, they work in both cooler and wetter weather than other bee species and excel at pollinating sunflowers, cucurbits, some brassicas, and some solanaceous crops (tomatoes and eggplants).
Sweat Bees: Often overlooked because of their size and solitary nature, these bees rank among the most common garden pollinators. They frequent most major vegetable seed crops, including crops like onions and carrots that other pollinators do not find inviting. They also visit sunflowers, cucurbits, and brassicas.
Butterflies have excellent vision and are thus drawn to bright colors, including reds and oranges. Asteraceae (sunflower, coneflower, artichoke, thistles, and dandelions) and lamiaceae (lavender, mint, and other herbs) are naturally appealing to these fluttering insects. Attracting butterflies, however, involves incorporating plants that serve the needs of all their life stages—specifically, places to lay eggs and form chrysalides, as well as food plants for larvae (caterpillars) and nectar sources for adults.
These busy insects bring many talents to the garden—they both control pests (like stink bugs) and pollinate a range of plants, from brassicas and alliums (onion, garlic, scallion, shallot, leek, and chives) to umbelliferous crops (celery, carrots, parsnips, fennel, dill, anise, parsley, and cilantro). Wasps do not exhibit floral constancy—or the tendency to visit a certain flower species—and, because of their short tongues, prefer blossoms with easily accessible nectar.
Some of the busiest pollinators, flies can transport large amounts of pollen, which they often pick up from nectar-producing flowers. They prefer shallow, open flowers with readily accessible nectar droplets. Flies generally have tubular, sucking mouthparts, which vary in length and limit which flowers different species will visit. They are drawn to umbelliferae (carrots, celery/celeriac, parsnip, and parsley), brassicaceae (cole crops, mustards, and Asian greens), rosacea (strawberry, raspberry, and blackberry), and alliaceae (onions, leeks, and chives), many of which also happen to be unattractive to bees.
Learn More About Pollinators
This page is adapted from the following texts
- The Seed Garden: The Art and Practice of Seed Saving, edited by Lee Buttala and Shanyn Siegel and published by Seed Savers Exchange
- “Native Pollinators in the Midwestern Seed Saving Garden,” an informational guide published by Seed Savers Exchange
- United States Department of Agriculture/United States Forest Service website