Scarification and pre-chilling requirements for germination of the native forb Utah trefoil (Lotus utahensis Ottley)

Authors: Jones, Thomas; Bushman, Shaun; CROCKETT, R - Natural Resources Conservation Service (NRCS, USDA); Forsyth, Kyle

Submitted to: Native Plants Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2022
Publication Date: 7/15/2022
Citation: Jones, T.A., Bushman, B.S., Crockett, R.T., Forsyth, K.C. 2022. Scarification and pre-chilling requirements for germination of the native forb Utah trefoil (Lotus utahensis Ottley). Native Plant Journal. 23(2):148-155. https://doi.org/10.3368/npj.23.2.148.
DOI: https://doi.org/10.3368/npj.23.2.148

Interpretive Summary: Native grass species currently dominate restoration seeding mixes, as they are generally more economical, easier to grow, and easier to harvest for seed compared to native forbs. However, an increased forb component in seeding mixes would enhance biodiversity and aesthetics, stabilize soils, and provide nutrition for insects and wildlife. For Utah trefoil to be commercialized, its germination biology must be elucidated to determine whether and how its seed must be treated to realize successful stand establishment. Germination was stimulated by acid scarification to break physical dormancy caused by a hard seed coat followed by prechilling to break physiological dormancy. However, stands must still be greatly improved for Utah trefoil to be adopted as a restoration species.

Technical Abstract: Increased numbers of native forb species are desired to diversify the structure and functioning of restoration-seeded plant communities in the Intermountain West. Utah trefoil (Lotus utahensis Ottley) is a perennial legume native to the southern portions of this region, but its germination and establishment are untested. To determine if seed dormancy is present, we tested combinations of acid scarification and prechilling in 2 laboratory experiments. The control treatment yielded only a negligible number of germinants, 0.3% in both experiments, indicating the presence of seed dormancy. When applied alone, acid scarification failed (P > 0.05) to increase germination in either experiment. Similarly, prechilling, intended to mimic overwintering conditions, failed (P > 0.05) to increase germination beyond the control in the first experiment, though it generated a small (P < 0.05) increase in germination (to 4.6%) in the second experiment. Nevertheless, when the 2 treatments were applied sequentially, germination increased to 56.9 and 73.6% in the 2 experiments, respectively. Two field experiments were conducted to verify laboratory results. When seeded in fall for spring germination, the acid-scarified treatment resulted in more (P < 0.05) established seedlings than the unscarified treatment (3.10 vs. 0.06%). When seeded in spring, acid-scarified seeds again established more seedlings than unscarified seeds (0.59 vs. 0.00%). Germination of Utah trefoil was facilitated by acid scarification followed by prechilling (or overwintering), indicating the presence of physical and physiological seed dormancy, respectively. However, field stands must be greatly improved for establishment to be satisfactory.