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nw frozen seeds

Can Frozen Seeds Survive for Centuries? We’re Banking on It

In the race to save native plants like purple New England aster and fragrant American mountain mint, the Chicago Botanic Garden freezes seeds for future use—but will frozen seeds be able to grow after hundreds of years in storage? Researchers are trying to find out.

Environmental threats such as climate change have caused thousands of plants to become rare or endangered. The tallgrass prairie, which has lost 96 percent of its land to agriculture and other human activities, is one of the earth’s most endangered habitats. By preserving seeds in the Garden’s Dixon National Tallgrass Prairie Seed Bank, researchers are working to ensure that native species don’t disappear in the wild.

Inside the seed vault at the Dixon National Tallgrass Prairie Seed Bank.

In winter 2015–16, two students from the Garden’s graduate program, which is offered in collaboration with Northwestern University, helped with the Seed Bank’s first germination trials. In the trial, a sampling of our oldest seeds was removed from deep freeze—a vault at minus 4 degrees Fahrenheit—and placed in favorable growing conditions to see if they would germinate after 13 years of dormancy.

The results? Species such as New England aster (Symphyotrichum novae-angliae), water speedwell (Veronica comosa), and American mountain mint (Pycnanthemum virginianum) germinated well. Species such as enchanter’s nightshade (Circaea lutetiana) and New Jersey tea (Ceanothus americanus) did not germinate; more research is needed to determine whether these seeds did not germinate because we were unable to figure out how to break their dormancy.

Seed sample sizes for trial were either 24, 60, or 75 seeds, depending on the number of seeds in the collection.

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The results show that seed collection is an efficient and cost-effective way to preserve biodiversity for future generations; experts predict that many of our native seed can survive hundreds of years in a seed bank (we’ll repeat the germination test in another ten years). Meanwhile, if you’re interested in joining our team and helping with the critical work of seed collection or banking, contact us.

©2016 Chicago Botanic Garden and

Published by

David Sollenberger

David Sollenberger is an ecologist at the Chicago Botanic Garden and currently manages the Dixon National Tallgrass Prairie Seed Bank. The Seed Bank’s mission is to conserve the floral diversity of the tallgrass prairie region by systematically collecting native seeds across the region and preserving them in long-term cold storage. View all posts by David Sollenberger

The Frozen Garden: Securing Seeds for the Future The Berry Botanic Garden and the U.S. Forest Service Pacific Northwest Region

Collecting Astragalus peckii seeds. Photo by Andrea Raven.

Collecting Lomatium bradshawii seeds. Photo by Andrea Raven.

Berry Botanic Garden Seed Bank freezer. Photo by Ed Guerrant.

Chrysothamnus viscidiflorus seedlings. Photo by Andrea Raven.

During hard times, it can be a comfort to know that you have money in the bank. Likewise, for land managers and concerned citizens, it can be a comfort to know that there is genetic material secured in a seed bank. Instead of saving cold cash, botanists around the globe are saving seeds and depositing them into cold storage. Forest Service botanists work in partnership with botanic garden professionals to cultivate frozen gardens: seed banks can serve as a key part of efforts to conserve wild plants.

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Seed banks serve as a complement to on-site care of rare plants and habitats. Stored seed can enhance restoration efforts and make the critical difference between extinction and conservation in the wild. Botanists collect genetically representative samples from vulnerable wild plant populations. Seeds are transported to a botanic garden, carefully processed, and then placed into heat-sealed foil laminate bags for long-term frozen storage. Seeds can be withdrawn from the bank in order to conduct conservation-related research or grow plants for a reintroduction. Struggling wild populations can be strengthened by the addition of new plants. Perhaps more important, when a population goes extinct in the wild, there are no options available for their conservation unless there is stored genetic material.

The Pacific Northwest is home to two seed banks that focus on securing rare native plants: Rae Selling Berry Seed Bank & Plant Conservation Program, Portland State University (formerly, The Berry Botanic Garden) in Portland, Oregon, and the University of Washington Botanic Gardens in Seattle, Washington. Each garden is a participating institution of the Center for Plant Conservation with a primary mission of working within an integrated conservation community.

Since 1983, The Berry Botanic Garden has been working to cultivate a very special frozen garden, the Seed Bank for Rare and Endangered Plants of the Pacific Northwest. Currently, more than 14,000 accessions (sets of seeds) containing almost 3 million seeds have been secured. An accession can contain more than ten thousand seeds or only a single seed. Those seeds represent 350 of the region’s most vulnerable plants, including all of Oregon’s extant federally listed and state listed plants and many of Washington’s, Idaho’s and California’s listed plants.

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Partnership between the Forest Service and The Berry Botanic Garden has resulted in a significant contribution to Berry’s seed bank. Botanists from all National Forests in Oregon have deposited seeds of rare native plants into the frozen garden, as have botanists from National Forests in Washington, Idaho and California. More than a third of the accessions in our frozen garden contain seeds from Forest Service lands. Over half a million seeds in those accessions provide an “insurance policy” for more than 100 rare plants under Forest Service management.

In this time of global climate change, such partnerships are critical. Many plant communities are dynamic and some are or will be adaptable to changing conditions. Certain plants, however, are more vulnerable to environmental changes. Such plants include those with inflexible physiological responses to climate characteristics, plants with infrequent reproduction, long-lived plants, plants with poor dispersal abilities, plants with restricted ranges, plants that are dependent on other species (for instance, pollinators), and plants with no options for relocation, such as those adapted to mountain top conditions. Locally, our situation requires quick action, as there is evidence that the American West is heating up faster than the rest of the country.

With this in mind, the Forest Service and The Berry Botanic Garden are taking the next step and focusing on seed collection of rare alpine plants. We will collect seeds from vulnerable population on two Forests in 2008: Willamette and Mt. Hood National Forests. Securing seeds off-site will provide land managers with additional options, should climate change or other factors affect those populations. With this partnership and others, we will continue to “grow” the frozen garden.