Breaking Dormancy and Increasing Restoration Success of Native Penstemon Species Using Gibberellic Acid Seed Coatings and U-Shaped Furrows

Abstract

Many plant species exhibit strong seed dormancy. This attribute benefits the species’ long-term survival but can impede restoration when rapid establishment is required. Soaking seeds in gibberellic acid (GA3) can overcome dormancy and increase germination but this treatment may not be effective outside the laboratory. An easier and potentially more effective method to apply this hormone is to coat seeds with a GA3-impregnated polymer. Seed dormancy can also be mitigated by creating a favorable microsite with increased soil moisture. We compared the emergence and establishment of penstemon seeds coated with GA3 to those of uncoated seeds planted in shallow drill rows versus deep, U-shaped furrows. Overall, 6 times more Palmer’s penstemon (Penstemon palmeri; p < 0.01) and 21 times more thickleaf penstemon (P. pachyphyllus; p < 0.001) established when coated with GA3, but GA3 coating did not affect the establishment of firecracker penstemon (P. eatonii; p = 1). Establishment was higher from deep furrows than shallow rows (p < 0.001). These results indicate that GA3 seed coating and deep, U-shaped furrows may improve the restoration success of some native forbs by breaking dormancy and providing a favorable microsite. Land managers could use these techniques to restore native forbs in dry, disturbed areas.