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

Abstract

Additional native forb species are desired to diversify the structure and functioning of restoration plant communities in the Intermountain West. Utah trefoil (Lotus utahensis Ottley [Faba-ceae]) 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 germinated acid-scarified and (or) prechilled seed plus an untreated control in 2 laboratory experiments. In both experiments, the untreated control yielded only 0.3% germinants. Likewise, when applied alone, acid scarification failed (P > 0.10) to increase germination in laboratory experiment 1, while increasing (P <0.10) it only slightly (to 1.8%) in experiment 2. Similarly, pre-chilling, intended to mimic overwintering conditions, failed (P>0.10) to increase germination in experiment 1, while generating only a small (P <0.01) increase (to 4.6%) in experiment 2. Nevertheless, when the 2 treatments were applied sequentially, germination increased to 56.9% and 73.6% in the 2 experiments, respectively, implying combinational (physical, that is, hard seed + physiological) seed dormancy. Two field experiments were conducted to verify laboratory results. In a fall-dormant planting seeded for spring germination, acid scarification resulted in more (P <0.0001) established seedlings than did unscarification (3.10% compared to 0.06%). When seeded in spring, acid scarification again yielded more (P <0.0001) seedlings than from unscarification, though numbers were lower (0.59% compared to 0.00%). In summary, acid scarification followed by laboratory prechilling (or field overwintering) greatly facilitated germination (or seedling establishment), overcoming combinational seed dormancy, but seedling establishment in the field was low.