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Back to News Learnings – April 19, 2021


Native Bee Survey

A bumblebee on the Appalachian Red eastern redbud tree's spring blooms.

A bumblebee on the Appalachian Red eastern redbud tree’s spring blooms.

Results are in from one of the most significant studies ever completed on Delaware’s bees. From 2018-2019, Mt. Cuba Center partnered with Matthew J. Sarver of Sarver Ecological to scientifically measure which species of bees were attracted to our gardens and natural lands to better aid in bee conservation.

Surprisingly, several species were found that were not previously known to occur in the First State. This supports the theory that, if you plant it, they will come. And by it we mean native plants that build healthy habitats for native bees.

Read on for the executive summary or click below to read the full report.

Read the Report

Executive Summary
by Matthew J. Sarver, Principal, Sarver Ecological, LLC

This study of Mt. Cuba’s gardens and outlying natural lands documented 3,493 individual bees of 135 species during 2018-19. Due to the diverse and special nature of Mt. Cuba, as well as the fact that Delaware has generally been under sampled for bees, this project represents one of the most important bodies of information ever compiled for Delaware’s bees.

Among the important results were a number of very exciting finds, including:

Project Highlights

  • 15 species of native bees – more than 10% of the species found – were not previously known to occur in the state of Delaware (“New State Records”) See page 10.
  • Discovery of the only known population of the Alumroot specialist, the Summer Cellophane Bee, Colletes aestivalis in the northeast region. Nearest recent records are from the Shenandoah Mts. of Virginia. This rare species is of high conservation concern throughout the northeast. See page 11.
  • Major range extension of 365 miles for the Polemonium specialist Andrena polemonii, the Jacob’s Ladder Miner Bee and the first ever records east of the Appalachians. A robust population is fueled by the extensive Polemonium plantings in the garden. See page 22.
  • Major range extension of 350 miles for the masked bee Hylaeus fedorica, first ever record east of the Appalachians. This specimen has been sent to taxonomic experts in Toronto for DNA barcoding to confirm its identity. See page 12.
  • 23 species of pollen specialist bees that depend on one or a few plant genera for their survival. Several of these species had not been documented before in Delaware.

Key Recommendations

1. Monitoring: Continue to monitor native bee populations at Mt. Cuba.

  • Long-term monitoring: Repeat bee bowl surveys at the 4 permanent transect locations established in 2019 in the future, preferably for two years in a row, every five to ten years. Continue targeted surveys for remaining specialist bees that have not been documented to date and continue to expand the sample size of surveys on native plant species.

2. Plant Selection in the Gardens: Incorporate bee diversity and host plants of specialist bees into decision-making about volumes of plant material in the gardens. See pages 25-30.

  • Maintain high floral area for important host species of rare and uncommon bees, including Polmemonium reptans, Uvularia , Penstemon spp., and others.
  • Increase floral area of the straight species Heuchera americana to support the regionally significant Colletes aestivalis population and promote americana as a straight species in the nursery trade.

3. Natural Areas Restoration and Plant Selection: Incorporate bee diversity and host plants of specialist bees into decision-making about volumes of plant material in natural areas restoration. See pages 25-30.

  • Focus heavily on increasing the floral area and diversity of late summer and fall composites (Solidago, Symphyotrichum, Vernonia, Helianthus, Cirsium, etc.) as appropriate. Helianthus is likely a particularly important gap to fill as it is underplanted and does not seem to “turn up” on its own very often.
  • Plant woody species such as Salix, Cornus, and Rubus that support bee diversity as well as specialist bees in shrub and edge plantings.

4. Education and Outreach: Incorporate the findings of this work into education and outreach components for garden visitors and conservation landowners.

  • Create educational publication on native bees and the plants that support them.


Due to the high density and diversity of native plant species in Mt. Cuba’s naturalistic gardens, as well as the extensive contiguous natural areas (including floodplain habitats of the Red Clay Creek and rare habitats like Piedmont seepage meadows), management and strategic restoration of Mt. Cuba lands has unique potential to host important source populations of a number of rare native bee species. Mt. Cuba also presents an unusual opportunity for long-term longitudinal study and monitoring of native bees at permanent sites. Mrs. Copeland’s vision has proven to be not only a world-class native plant garden, but a critical ark for the native bee fauna of the Piedmont. We look forward to continuing to work with Mt. Cuba to better understand the native bees of this ecoregion and their critical relationships with our native flora.

Sarver, Matthew J. 2020. Mt. Cuba Native Bee Survey 2018-2019 Final Report. Report to Mt. Cuba Center. Sarver Ecological, LLC: Wilmington, DE.