By Lisa Mason, CSU Extension Horticulture Specialist, Entomologist

Pollinators in Vegetable and Herb Gardens

Pollinators are critical for plant reproduction in approximately 1/3 of the human diet, or every 1 in 3 bites of food. Research shows that 87 food crops rely on pollination from animals (e.g., bees and other insects, birds, bats and other mammals, and more) (Klein et al., 2007; National Research Council, 2007; USDA.gov, 2024). Many of those crops grow around the world like cinnamon, figs, vanilla, and cacao beans that make chocolate. Many of those crops grow in other parts of the United States such as almonds, cranberries and citrus fruits. What about crops that grow in Colorado gardens? 

Cucurbitaceae Family – Gourd and Cucurbit Plants

Squash, gourds, pumpkins, cucumbers, watermelons, cantaloupe and other plants in the Cucurbitaceae family rely on pollinators for plant reproduction. Many of the crops are monoecious, meaning the plants have separate male and female flowers on the same plant. Pollinators transfer the pollen from male flowers to the female flowers. A female flower can be differentiated from a male flower by the small fruit at the base of the flower.

Pollination biology can be even more complex! For example, cucumbers are monoecious, however newer varieties are gynoecious, meaning they were bred to produce only female flowers. These varieties still need to be pollinated from male flowers so usually monoecious seeds are included with the gynoecious seeds. Typically, gynoecious varieties will produce a higher yield than monecious varieties. Some seedless varieties of gynoecious cucumbers produce fruit through a process called parthenocarpy, meaning pollination/fertilization is not required for the plant to produce fruit.

Bees are the primary pollinator for plants in the Cucurbitaceae family. Squash bees (Xenoglossa spp. and Eucera Peponapis pruinosa) are among the most efficient pollinators of pumpkins and squash. These native bees can be seen flying around in the early mornings visiting squash flowers. Squash bees are underground nesters. If holes are visible in the garden bed or nearby bare soil, watch for squash bees or other native bee nesters. Since these bees live a solitary life, they will not sting or pester humans like some social insects (e.g., yellowjackets).

Honey bees will visit a variety of cucurbit crops, but often native bees are more efficient at pollinating specific crops. Research on watermelon pollination documented 23 native bee species in the California watermelon crops, and they transferred more pollen than honey bees (Xerces Society, 2018).

Solanaceae Family – Nightshade Plants

Plants in the Solanaceae family include peppers, tomatoes, eggplants, tomatillos and more. Some varieties of tomatoes and other plants can self-pollinate. The flowers are considered “perfect,” meaning male and female parts are in the same flower. Many of the plants require movement for pollen to be released from the plant. Bumble bees can “buzz pollinate” a plant, meaning they have a specific vibration that will release the pollen from a plant when they are on it. They are among the most efficient pollinators for plants in the Solanaceae family. Greenhouse growers often use bumble bees to pollinate crops in greenhouses.

Herbs

Many herbs will attract a wide variety of pollinators and beneficial insects. Examples of herbs that attract pollinators include lavender, dill, mint, basil, borage and oregano.

Dill, fennel and parsley are caterpillar host plants for the black swallowtail butterfly, an often-welcome visitor in home gardens. Caterpillars consume a significant amount of plant material to complete their development which may alarm home gardeners who wish to harvest the plants for their own use. Consider finding a balance of leaving some plants for caterpillars and protecting the other plants. Netting over the plants designated for the caterpillars will help. Bonus: Netting will also protect the caterpillars from being preyed on by the invasive European paper wasp, a common occurrence in gardens.

Keep in mind, if the goal is to harvest herbs for culinary or medicinal use, consider cutting off the flowers before they bloom. This method will allow the plant to focus on leaf production rather than flowering. When growing lavender, harvest the flowers just before they open. If the goal is to attract pollinators, consider a balance of leaving some plants to bloom for pollinators, while maintaining some plants for harvest.

Other Vegetable Crops

Most other vegetable crops do not require pollination from insects or animals. Some crops like corn plants are wind pollinated. The corn tassel, or the male part of the plant, produces massive amounts of pollen. Pollen grains need to land on a silk (e.g. the “hairs” on the corn), the female part of the plant. Each silk that is pollinated develops into a kernel of corn. Even though corn is wind-pollinated and doesn’t produce nectar, bees can still be observed collecting pollen grains from corn plants.

Build Pollinator Habitat with Your Vegetable Garden When planning your vegetable garden for next season, consider adding some pollinator-friendly plants nearby to attract a wide variety of pollinators and other beneficial insects. Flowers that produce nectar may also attract insects that will prey on garden pests. When planning for vegetables and pollinators, keep in mind the water and soil requirements. Vegetable plants tend to have higher water and different soil requirements than pollinator-friendly plants. For more information, click here. For questions, reach out the Arapahoe County Extension office and talk to a Master Gardener at 303-730-1920, or email at mastergardener@arapahoegov.com.