A cliff-hanger of a survival story: Jesup’s milk-vetch
Ice, floods, drought, and invasions–and this rare plant hangs on!
The endangered plant clings by its small roots to silt-filled crevices in the steep rock outcrops along the Connecticut River. Jesup’s milk-vetch (Astragalus robbinsii var. jesupii) naturally occurs in only three locations, all along the river’s high water line between Vermont and New Hampshire.
Milk-vetches are part of the legume family, like peas and beans. With leaves comprised of many small leaflets, the Jesup’s milk-vetch has a slight resemblance to a fern. Bunches of small violet flowers bloom from these leaves in early May, followed by nearly inch-long pea-like sea pods in June.
By 1987, when the Jesup’s milk-vetch was listed under the Endangered Species Act, there were less than 1,100 plants at only three sites in the world.
A strong partnership between the two states has helped the species survive, supported in part by federal funding provided to states under Section 6 of the Endangered Species Act. State agency staff works with partners to evaluate threats and implement recovery actions.
“Jesup’s milk-vetch is certainly a survivor,” said botanist Bob Popp with the Vermont Department of Fish and Wildlife Natural Heritage Inventory. “The plants have to withstand summer heat and drought, winter ice scour and spring flooding.”
Bob works on the milk-vetch with intrepid botanists from New Hampshire Natural Heritage Bureau, the U.S. Fish and Wildlife Service, the Native Plant Trust and private groups.
Each year, the team visits the sites on both sides of the river to count and monitor the surviving plants. During the visit, the team also plants new seedlings to augment the natural population at two sites. The seeds were collected from the wild plants, germinated over the winter by the Native Plant Trust, and returned to the population where they were collected.
They note the extent of invasive plant species and use the data along with hydrologic and climatologic data from the year to evaluate the impacts to milk-vetch populations and plan their strategy for upcoming years.
For years, the team was unable to get any significant survival of transplants to augment the natural population, Popp explained. But now they have.
The years following the augmentation with transplanted seedlings initially yielded discouraging results. In 2012 and 2013, on about ten percent of transplants survived to the following spring. Despite this, the team held out hope for the following year, and found not only five wild plants growing along the river, but 22 transplants growing lushly with many even in bloom. The team eagerly looked back at their records to evaluate methods and climatological data to learn what factors had brought such high success.
“We think that we have finally developed a protocol to successfully augment the two populations and introduce more new populations.”
Following the 2013 success, biologists successfully established Jesup’s milk-vetch at a new site at Silvio. O Conte National Fish and Wildlife Refuge in New Hampshire! From 2014 to 2016, biologist transplanted 47 seedlings and by June 2020, the site had grown on its own to 93 plants. With a life cycle lasting only three years, this means the original transplants thrived and successfully reproduced.
In 2020, the Vermont Department of Fish and Wildlife secured funding through a Service Recovery Challenge Grant to attempt to introduce additional populations and boost plant survival by managing invasive species. Establishing Jesup’s milk-vetch in different locations allows the species more opportunities to survive and reproduce while also ensuring the species would survive if plants at one or more sites were extirpated by a catastrophic event, such as flooding or extreme drought.
In 2020, more seedlings were introduced in a new location on the refuge, and 35% managed to survive the summer’s harsh and dry conditions. In 2021, Vermont Department of Fish and Wildlife along with partners will continue to work to establish new sites within the Connecticut River watershed and on the refuge as they work towards securing the future of the species.
Currently, biologists are learning more about Jesup’s milk-vetch through genetic research that will help with future introductions. This would not be possible without the continued efforts of our partners, including Vermont Department of Fish and Wildlife, The Native Plant Trust, New Hampshire Natural Heritage Bureau and private groups.
