SEED PROPAGATION SEED BAN K ING FOR THE FUTURE Andrea N. Raven (503) 636-4112 [email protected] The Berry Botanic Garden 11505 SW Summerville Avenue Portland, OR 97219 Abstract The Berry Botanic Garden acts as a regional resource within the plant conservation community by maintaining a seed bank for rare and endangered native plants. Banked seeds represent an “insurance policy:” should wild populations be damaged or disap- pear, we hope to be able to provide the genetic material to enhance or re-establish those populations. The process of banking involves seed collection, cleaning, drying, packaging, freezing and documentation. Seeds can be withdrawn from the bank for reintroductions or scientific research. To effectively perform our seed banking, we work in cooperation with many individuals and organizations. Keywords endangered species, reintroduction, ex situ research, native plants Introduction One of the primary missions of The Berry Botanic Garden, located in Portland, Oregon, is to conserve rare and endangered plants native to this region. We serve as a resource for rare plant work in this region by specializing in ex situ, or off-site, conservation research. Our ex situ work includes rare plant seed storage, germination testing, propagation research, including tissue culture, the maintenance of living col- lections and common garden experiments (Guerrant 1997). All of these are intended to complement on-site efforts. In addition, we perform in situ or on-site research. Our on-site research will not be addressed in this article. We work in cooperation with many individuals and organizations to carry out our mission. We are a charter member of the Center for Plant Conservation (CPC), which is a national network of 28 botanic gardens and arboreta interested in conserving sensi- tive species. The Berry Botanic Garden represents the Pacific Northwest region within the CPC network. As such, we work with rare taxa from Oregon, Washington, Idaho and portions of California and Nevada. We also belong to the American Association of Botanic Gardens and Arboreta and the American Association of Museums. We regularly work in partnerships with city, state and federal agencies, and with private conservation groups such as The Nature Conservancy. In addition, we depend heavily 7 SEED PRO P AGATION on volunteers and interns. procedures are less effective or inap- cies?, how many individuals should be propriate for some taxa. sampled per population?), how many The heart of our conservation program propagules should be collected per is the Seed Bank for Rare and Endan- individual? and under what circum- gered Plants of the Pacific Northwest. Seed Banking Procedures stances is a multiyear collection plan The bank was the brainchild of Molly An overview of the process of seed indicated? We attempt to balance the Grothaus, a former board member, and banking is as follows: we collect seeds, need for genetically and geographically was established in 1983 with a grant document the collection, dry, clean representative samples with the possi- from a local foundation (Fred Meyer and count seeds, weigh and pack- bility of damaging a given population Charitable Trust). Julie Kierstead Nel- age seeds, and if resources allow we by overcollecting or causing physical son was the first Conservation Director germinate a portion. Our procedures damage through trampling. We use and Seed Bank Curator at Berry. follow standards developed by the collection guidelines established by the We consider our seed bank to be an International Board for Plant Genetic Center for Plant Conservation to assess “insurance policy” within an integrated Resources (Cromarty et al., 1982; El- whether we have a genetically represen- conservation community. With the lis et al., 1985a and b) and the Center tative sample (CPC, 1991). In most for Plant Conservation (CPC, 1991; help of many individuals and orga- cases, the CPC recommends sampling Wieland, 1995). nizations, we are working to bring a range of one to five populations per genetically representative samples of The first issue we address when bank- taxon, ten to 50 individuals per popu- this region’s rarest and most vulnerable ing is determining which species to col- lation and one to 20 propagules per plants into long-term storage and to lect. We work in cooperation with the individual. We choose the appropriate maintain those seeds. Should a wild Natural Heritage Programs, an essen- sample sizes for each taxon based on population become extirpated, we tial resource. The Heritage Programs biological and management-related hope to be able to provide the neces- gather and store population-specific in- factors (such as the intended use of sary genetic material and propagation formation on rare and sensitive plants seeds for reintroduction). knowledge to re-establish the popula- for each state. They have generously We obtain seeds from a variety of tion. Stored seeds can also be used to provided us with detailed summaries sources. Federal botanists (Bureau of enhance damaged populations. on the region’s rare plants and we use Land Management, Forest Service, their data to prioritize plants by level U.S. Fish and Wildlife Service) collect Seed banking by itself does not con- of endangerment. In addition, we work over half of our seeds. Berry Garden stitute conservation of a population in cooperation with regional land staff members, interns and volunteers or taxon. We believe that seed banking managers (such as the Forest Service, is a tool that is part of a coordinated Bureau of Land Management and U.S. collect a great number of seeds. Other community effort to conserve our Fish and Wildlife Service) and other professionals, including university native plants. We would caution that knowledgeable people to determine professors and students, Nature Con- the science of storing seeds is still which plants they are most interested servancy staff and specially trained being developed and, even when the in banking. Native Plant Society members collect proper technology is used, stored seed for us as well. All collection is done The next issue we address is a deter- samples can still be inadequate for using the appropriate permits and with mination of appropriate sample sizes. reintroductions or other desired uses landowner permission. Key questions that must be answered (for instance, samples sizes can be too when sampling rare plant populations Seeds are rapidly transported to the small or the genetic mix can be inap- include the following: how many Garden and immediately placed in the propriate). Optimal storage conditions populations should be sampled per spe- Seed Vault, a walk-in, drying facility vary for each taxon. It is likely that our 8 SEED PRO P AGATION that we had constructed specifically for viability, and those with low germi- (diamonds) and accessions (bars) for seed banking. Seed moisture level nation must be replaced. Seeds are also through time (1998 data not shown). and storage temperature have been removed for other purposes, such as As time passes, it becomes more dif- identified as being the main factors scientific research and reintroduction, ficult to add new taxa to the bank and influencing long-term seed viability. and those must be replaced as well. hence, the number of taxa represented Currently, the experts are debating We attempt to use small numbers of has leveled off in recent years. On the over optimal relative humidity (RH) seeds for our germination tests, since other hand, there has been a recent levels and temperatures (Ellis et al., they are rare. We also use seeds for dramatic increase in the number of 1991; Smith, 1992; Vertucci and Roos, tissue culture research. Through our banked accessions due to a shift in 1990, 1991, 1993). The internation- tests, we hope to gain information collecting methods. Currently, we ally accepted procedure has been to on germination requirements for rare collect a greater number of accessions dry seeds to equilibrium at 15% RH plants, since that information is usually for a given population, each accession and 15°C. In recent years, researchers not available. The results of our on- representing a single individual. Older from the USDA National Seed Stor- going tests are available to interested accessions were often bulk collections, age Laboratory in Fort Collins, CO professionals. with one accession representing seeds have challenged this, arguing that from many plants collected at one those conditions dry seeds too much time. and can reduce seed survivorship and Seed Bank: Past, Present and Future One example of our work with rein- seedling vigor. We have attempted to troduction involves the Malheur wire take a conservative approach and our In 1983, we created the bank with 73 lettuce, Stephanomeria malheurensis vault is maintained at a temperature accessions of 60 different plants. Cur- (Asteraceae), one of Oregon’s rarest of 15°C with relative humidity at ap- rently, the bank contains over 4,000 plants. It is an annual and is known proximately 22%. accessions representing over 280 taxa. from only a single location in eastern The vault is surrounded by 8” of Each accession contains seeds from Oregon. In 1985 and 1986, wild concrete to reduce the threat of fire a separate population or individual. plants did not appear and the Fish damage. Air inside the vault is con- Figure 1 shows the increase in taxa and Wildlife Service contacted Berry. stantly circulated and we use silica gel as a desiccant. We generally allow seeds to dry for a minimum of one month, although the length of time varies depending on seed size, seed oil content and the total amount col- lected. During the drying period, seeds are removed from the vault and we clean and count them. After drying is completed, we weigh and heat-seal the seeds inside metal foil pouches. The pouches are then placed into a modified chest freezer at –18°C for long-term storage.