How to pick cultivars for pollinators
by Emily Erickson for Tufts Pollinator Initiative
What is a cultivar and why should I care?
Unless you are going out of your way to buy your plants from a specialty nursery, chances are you are purchasing a “cultivar,” or a plant that has been bred for desirable traits like the number of petals, flower shape, or flower scent. Plant breeding is not inherently a bad thing: it broadens the diversity of species that you can grow in your garden by improving resilience against pests, drought, or poor soils. As a result, cultivars have become the industry standard. They can be identified by the single quotation marks in the name (ex. Marigold Alumia ‘Flame’).
While cultivars are great for people, they are not always great for pollinators. Native plants and their pollinators share a long evolutionary history, and many flowers have evolved particular traits that signal honest advertisements of a high quality food resources. For instance, the smell and color of wild geranium tell a bee that that nectar and pollen awaits and the dark lines on the petals help them to quickly locate their meal.
In contrast, cultivars have been removed from evolutionary history with insects; humans have bred cultivars in labs and greenhouses to meet our aesthetic preferences. And sometimes, by selecting for traits that we deem impressive, we inadvertently produce plants that broadcast false advertising. Recent work, including my PhD research, has demonstrated how cultivars—even ones that look quite visually similar—can vary dramatically in the abundance and diversity of insects that they are able to support, so it’s important to choose carefully.
5 tips for choosing better cultivars
But, how do you choose? Ideally, all ornamental cultivars would scored for pollinator attractiveness to help guide customers to select high-value plants for their flower gardens. A metric like this doesn’t yet exist, however, so we’ve distilled down some basic guidelines that you can use to identify the best plants for flower-visiting insects!
1. Avoid doubled flowers
Double-flowered varieties are those that have been selected for extra petals, such as in many roses, impatiens, chrysanthemums, and carnations. Often, this doubling comes at a cost: the reproductive florets (where pollen and nectar are produced) are converted to petals, meaning the flower no longer feeds pollinators! And, even if the plant is still capable of producing rewards, doubling often obstructs visitor access to those resources. So, while doubled varieties are interesting to look at, they are best left on the shelves.
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