A Helpful Headstart
By Dr. Emily Geest, Postdoctoral Fellow at the Oklahoma City Zoo
An important aspect of monarch butterfly conservation is ensuring habitat exists for monarchs throughout their range. Monarchs need two kinds of habitat; nectaring habitat for adult butterflies and hostplant habitat for caterpillars (larvae). For monarchs the only hostplant they use are plants that fall within the milkweed family. Globally there are over 200 species milkweeds that fall in the genus Asclepias named after the ancient Greek god of medicine.
In Oklahoma, we have over 25 species of milkweeds including regularly encountered species such as green antelophorn (Asclepias viridis), butterflyweed (Ascelpias tuberosa), and antelopehorns (Asclepias asperula). However, not all species are common with some species, such as dwarf milkweed (Asclepias involucrata) in the Oklahoma panhandle thought to be extirpated and some species in the southeastern corner, such as purple milkweed (Asclepias purpurascens) considered critically imperiled at the state level through NatureServe, a national biodiversity database.
In an effort to bolster these rare Oklahoma milkweed populations, researchers at the Oklahoma City Zoo and Botanical Garden have launched a milkweed headstart project. Teams consisting of horticulture and milkweed experts are using historical data to travel to remote portions of the state to survey for these milkweed species, collect seeds from established plants, and grow seedlings at the OKC Zoo’s greenhouses in order to plant seedlings in secure locations in the future.
Initial trips began in spring of 2023 with surveys in the panhandle focused on finding dwarf milkweed (Asclepias involucrata), wheel milkweed (Asclepias uncialis), and long-hood milkweed (Asclepias macrotis). While the panhandle milkweed species were found unsuccessfully, a grasshopper not seen in Oklahoma for over 65 years was identified during the trip!
For the southeastern corner of the state four species of conservation interest were located in May 2023 including purple milkweed (Asclepias purpurascens), green milkweed (Asclepias hirtella), red-ring milkweed (Asclepias variegata), and four-leaved milkweed (Asclepias quadrifolia). Located plants had GPS coordinates taken and a fine mesh bag placed over seedpods to collect a small portion of seeds available. In August 2023, the team returned to the locations and successfully collected seeds all four species. These seeds will be germinated at the OKC Zoo, with germination rates measured. In spring of 2024, seedlings will be planted in secure locations and monitored for survivability.
The ultimate goal of this headstart program is to help bolster the population of vulnerable to critically imperiled milkweed species in Oklahoma as well as inform conservationists on the biology of rare milkweeds and feasibility of milkweed headstart programs. The Zoo is working with multiple partners including Oklahoma State University, The Nature Conservancy, Oklahoma State Parks, Oklahoma Department of Wildlife Conservation, US Army Corps of Engineers, and USDA Forestry Service to identify milkweed species of conservation concern native to Oklahoma, gain access and permissions to lands, receive permits for collection, and plan sites for future seedling reintroduction. If the program proves to be successful, this headstart program will be used as a model for other threatened and rare plants in the state.