FINAL STUDY REPORT NRCS Materials Center, Corvallis, OR December 2017 Longevity of Scarified Seed of Three Native Legumes under Different Seed Storage Conditions Annie Young-Mathews, Kathy Pendergrass and Amy Bartow

ABSTRACT Seed mixes are often needed at short notice for revegetation or erosion control plantings, and many native Pacific Northwest legumes used for such plantings require mechanical scarification in order to obtain rapid, even germination. Mechanical scarification and seed storage conditions have the potential to affect the long-term viability of seed. Studies were conducted at the USDA Natural Resources Conservation Service Corvallis Plant Materials Center, Corvallis, Oregon to determine the response of riverbank lupine ( rivularis), broadleaf lupine (Lupinus latifolius), and rosy bird’s-foot trefoil (Lotus aboriginus) to seed storage environment and scarification treatment over the course of five years. Seed of all three legume species showed little response to either storage environment or scarification, retaining greater than 90% viability levels over the five years of the study. Results suggest that scarified legume seed might be maintained for several years in “ready-to-go” seed mixes, even under less than ideal storage conditions, thus facilitating rapid revegetation efforts when the need arises.

INTRODUCTION In western Oregon, seed mixes are often needed at short notice for revegetation of retired logging roads, road cuts, reseeding after fires, or for other erosion control plantings. The Salem and Eugene Districts of the Oregon Bureau of Land Management (BLM) were interested in developing simple seed mixes, including legumes and grasses, which could be seeded in projects on the west slopes of the Cascades and Coast Range in western Oregon. However, because it is often difficult to plan ahead for the amount of seed needed for each year’s projects, seed mixes may remain in storage for several years. Many of the legumes of interest for such plantings have hard seedcoats that require scarification in order to obtain quick and even germination, but there was concern that there would be reduced viability of seed once the seedcoat has been compromised. In 2009, the Oregon BLM developed an Intra-Governmental Order (IGO) with Oregon USDA-Natural Resources Conservation Service (NRCS) Corvallis Plant Materials Center (PMC) to develop seed mixes for revegetation in western Oregon, including recommendations for seed treatment, seed storage, and planting protocols to achieve optimal seedling establishment. The three legumes of interest, riverbank lupine (Lupinus rivularis Douglas ex Lindl.), broadleaf lupine (Lupinus latifolius Lindl. ex J. Agardh), and rosy bird’s-foot trefoil (Lotus aboriginus Jeps., also known as Hosackia rosea Eastw. or Lotus crassifolius (Benth.) Greene var. subglaber

Annie Young-Mathews, Plant Materials Center Manager, 3415 NE Granger Ave, Corvallis, OR 97330, anna.young- [email protected] (Ottley) C.L. Hitchc.), are herbaceous perennials with fairly wide distribution in the Oregon Coast Range and western slopes of the Cascade Range at elevations up to about 7,000 ft (Young- Mathews and Darris, 2011; Darris and Young-Mathews, 2012; Jaster et al., 2017; USDA-NRCS, 2017). Based on container and seed production experience at the Corvallis PMC, riverbank lupine generally does not require scarification for fall planting or container production (Bartow, 2015), but has exhibited more even germination with scarification prior to spring planting. Percentage of hard seed in riverbank lupine varies widely depending on the population and year, but can range from 10 to 65% (Corvallis PMC, unpublished data). Broadleaf lupine has shown similar variability, ranging from 3 to 42% hard seed in different populations or years. Hot water treatment or mechanical scarification is generally recommended prior to seeding to aid in even germination of broadleaf lupine (Flessner and Trindle, 2003). While there is no published data on seed treatments or percentage of hard seed in rosy bird’s-foot trefoil, it may be similar to the closely related Lotus crassifolius, which generally requires both mechanical scarification and 60 to 90 days of cold, moist stratification to germinate (Young-Mathews and Darris, 2011). Hard seeded legume species are known to maintain viability for many years under optimal storage conditions. Some Lupinus species have been reported to maintain germinability for 6 to 24 years (Atabekova and Ermakova, 1973), while other hard seeded legumes such as alfalfa (Medicago falcata and M. sativa) stored for over 60 years were reported to germinate at rates of up to 48% and 30%, respectively (Wilton et al., 1978). However, a study on the storage of acid- scarified seed of the annuals Lupinus texensis and L. havardii showed that germination of the scarified seed declined rapidly after just four months of storage at 75% relative humidity (RH) and 72°F, but scarified seed stored at cooler temperatures (40°F) and lower RH (11-52%) maintained or increased in germinability after one year of storage (Mackay, 2005). Little is known about the longevity or storage requirements for scarified seed of riverbank lupine, broadleaf lupine, and rosy bird’s-foot trefoil. The objective of this study was to evaluate the longevity of scarified seed of these three legume species under different storage conditions. The outcome of this study will help determine whether “ready-to-go” seed mixes may be scarified in advance for restoration needs without a great loss of viability, and whether refrigerated storage is needed to maintain seed viability.

MATERIALS AND METHODS From 2012 to 2017, the Corvallis PMC conducted a study to evaluate the longevity of scarified legume seed stored in different storage environments. Two storage environments were evaluated: a controlled environment (walk-in seed cooler set at 45°F and 30–40% relative humidity) and an un-controlled warehouse-like environment (PMC headhouse with no temperature or humidity control, ranging from approximately 40 to 100°F and 30 to 100% RH). Seed lots used in this trial were provided by the Salem District of the BLM from 2008 harvests of western Oregon populations grown at the USDI-BLM Walter Horning Seed Orchard (NRCS accession numbers: Lotus aboriginus [originally labelled L. crassifolius] 9109149; Lupinus latifolius 9109150; and Lupinus rivularis 9109151). On 26 April 2012, seed lots for scarified treatments were run through a Westrup seed scarifier (Westrup, Slagelse, Denmark) at medium-high speed for about 6 to 8 minutes, until seeds looked dulled and seed coats were nicked. Seed viability was tested by tetrazolium (TZ) assay on 200 seeds per lot according to standard TZ protocols (AOSA and SCST, 2009; Grabe, 1970) at the Oregon State University (OSU) Seed Laboratory at the

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beginning of the experiment in May 2012 and six months later in November 2012. When greater than half of the treatments had higher TZ at the 6-month test than the original tests, TZ assays were repeated in December 2012. Due to continued inconsistencies in TZ results from the OSU Seed Lab, the 1-year tests were sent to both OSU and Tangent Seed Lab. The 2-year and 5-year TZ tests were both evaluated at the Tangent Seed Lab following standard TZ protocols.

RESULTS AND DISCUSSION Seed viability for the three species tested did not appear to decline appreciably after five years, regardless of scarification treatment or storage environment (Table 1). There continue to be inconsistencies in the TZ test results, as some seed lots apparently had higher viability after five years than when the experiment started. However, regardless of these questions with TZ testing, all seed lots have obviously maintained a high level of viability so far. Table 1. Viability of scarified and non-scarified seeds of three legume species stored in two storage environments over five years at the USDA-NRCS Corvallis Plant Materials Center, 2012-2017. ¥ Storage Storage duration (yr) Species Environment§ Trt£ 0 0.5 0.6 1 1 2 5

------%------Lotus aboriginus Cooler NS 96 97 96 94 92 100 99 S 97 95 83 94 97 100 98 Lupinus latifolius NS 83 98 93 65 96 88 99 S 78 95 81 65 93 87 96 Lupinus rivularis NS 87 92 80 49 95 90 96 S 80 97 76 62 94 83 95 Lotus aboriginus Headhouse NS 95 97 97 94 91 98 97 S 97 95 94 97 96 98 97 Lupinus latifolius NS 90 97 94 63 97 87 97 S 81 97 92 40 95 90 97 Lupinus rivularis NS 86 96 77 68 91 90 96 S 74 96 85 63 94 76 96 § Cooler, seed cooler with controlled atmosphere of 45°F, dehumidified to 30–40% RH; Headhouse, uncontrolled headhouse with temperatures ranging from approximately 40 to 100°F and relative humidity levels from 30 to 100%. £ Seed treatments, NS−non-scarified seed, S−mechanically scarified. ¥ TZ assays performed by OSU Seed Lab for year 0, 0.5, 0.6, and first year-1. TZ assays performed by Tangent Seed Lab for second year-1, year-2 and year-5 tests.

CONCLUSION Viability of all three legume species remained high over five years of storage, regardless of scarification treatment or storage environment, suggesting that “ready-to-go” scarified legume seed might be maintained for at least five years, even under less than ideal storage conditions.

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LITERATURE CITED AOSA (Association of Official Seed Analysts) and SCST (Society of Commercial Seed Technologists). 1993. Rules for testing seeds. Journal of Seed Technology 16(3):1-113. http://www.jstor.org/stable/23432704 Atabekova, A.I., and V.E. Ermakova. 1973. Germinability of lupin seeds of different age. Izvestiya timiryazevskoi sel'skokhozyaistvennoi akademii 1:62-67. Bartow, A. 2015. Propagation protocol for production of container (plug) Lupinus rivularis . USDA NRCS - Corvallis Plant Materials Center Corvallis, Oregon. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2017/11/21). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources. Darris, D., and A. Young-Mathews. 2012. Plant fact sheet for riverbank lupine (Lupinus rivularis). USDA-Natural Resources Conservation Service, Corvallis Plant Materials Center, Corvallis, OR. Flessner, T.R, and J.D.C. Trindle. 2003. Propagation protocol for production of container (plug) Lupinus latifolius Lindl. ex J.G. Agardh plants 7 or 10" cones. USDA NRCS - Corvallis Plant Materials Center, Corvallis, OR. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2017/11/21). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources. Grabe, D.F. (editor). 1970. Tetrazolium testing handbook for agricultural seeds. Handbook on seed testing, No. 29. Association of Official Seed Analysts of North America, Tetrazolium Testing Committee, Amherst, MA. Jaster, T., S.C. Meyers and S. Sundberg, eds. 2017. Oregon Checklist, Version 1.7. . http://www.oregonflora.org/checklist.php (accessed 2017/11/21). Mackay, W.A. 2005. Effect of scarification, seed storage temperature, and relative humidity on Lupinus havardii Wats. and Lupinus texensis Hook. seed germination. Hortscience 40 (3):782-785. Wilton, A.C., C.E. Townsend, R.J. Lorenz, and G.A. Rogler. 1978. Longevity of alfalfa seed. Crop Science 18(6):1091-1093. USDA, NRCS. 2017. The PLANTS Database, http://plants.usda.gov (accessed 21 November 2017). National Plant Data Team, Greensboro, NC. Young-Mathews, A., and D. Darris. 2011. Plant guide for big deervetch (Lotus crassifolius). USDA-Natural Resources Conservation Service, Plant Materials Center, Corvallis, OR.

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