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Growing Knowledge to Protect Pollinators

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Male small carpenter bee on yellow flower.

Small carpenter bees, Ceratina cucurbitina, are among the pollinator species that may use perennial stems for habitat. Image by gailhampshire, CC BY 2.0

Volunteers with the NC State Extension Master Gardener℠ program help grow knowledge of sustainable gardening practices by taking part in citizen science and research projects. 

An ongoing research project is investigating how to improve habitat for pollinators in residential landscapes. As some pollinators build nests for their offspring in hollow stems, Master Gardener℠ volunteers are helping determine if changing the way we manage herbaceous perennials in the landscape can provide more of this nesting habitat. 

According to project leaders Elsa Youngsteadt and Hannah Levenson, there is currently limited understanding of the best management practices for pollinator overwintering habitat. Through this project, they aim to develop a greater understanding of how plant management practices can maximize the ability of residential landscapes to provide habitat, as well as generate a list of plant species for gardens and ornamental plantings that pollinators utilize.

Brown stems that held last season's flowers stick up above new leaves emerging from green headed coneflower.

If managed with pollinators in mind, last season’s flowering stems can provide overwintering habitat for some species. Image by Charlotte Glen, NC State.

They are doing this by identifying the number, identity, and emergence time of pollinators from perennial stems collected by Master Gardener volunteers in their own landscapes or Extension demonstration gardens. Instead of cutting perennial stems all the way back in fall, which is the common practice, Master Gardener volunteers are leaving a few feet of stem standing above ground level through the winter and into the next growing season. They will then collect these old stems across four time points and send them to NC State where Elsa and Hannah will look for pollinators and identify any they find.

An initial pilot of this study has yielded promising results. Species that were found in stems from the pilot include Ceratina bees, also known as small carpenter bees, leafcutter bees, potter wasps, and earwigs. This year, the study is expanding to include additional sites in Chatham, Chowan, Perquimans, Cumberland, Forsyth, Lee, Vance, and Wilson counties. Look for recommendations based on the findings in future Extension publications, workshops, and plant profiles on the Extension Gardener Plant Toolbox.

A plant stem split open to reveal small black bees nesting inside.

Pollinator species found nesting in stems during the study pilot include Ceratina bees. Image by Elsa Youngsteadt, NC State.

This project is a partnership between NC State faculty in the departments of Horticultural Science, Entomology & Plant Pathology, and Applied Ecology, Master Gardener volunteers, and Extension agents based in N.C. Cooperative Extension centers in Chatham, Chowan, Perquimans, Cumberland, Forsyth, Lee, Vance, and Wilson counties. Many thanks to Leslie Rose, Extension horticulture agent in Forsyth County, for coordinating communications for this project. 

Infographic of statistics from

The Extension Master Gardener program is a statewide network of volunteers and Extension educators working in N.C. Cooperative Extension county centers and on NC State campus. Through education and outreach, we connect people with the benefits of gardening and empower North Carolinians to cultivate healthy plants, landscapes, ecosystems, and communities. 

Explore stories from our 2022 Annual Report, which celebrates our work to help North Carolinians learn and grow.

Join, support, or connect with Extension Master Gardener volunteers in your community.