Wildflowers - Lassen Volcanic National Park (U.S. National Park Service) Mules ear bloom beneath Mt. Diller NPS Photo. Alerts. Lassen Volcanic offers spectacular opportunities for wildflower viewing during the summer months. Blooming times vary each year and are greatly affected by the winter's snowpack. Blooming time also varies with each wildflower species. For example, mountain mules ear, snow plant, and western wallflower bloom earlier in the season, while California corn lily and silverleaf lupine tend to bloom later. Below are some rough estimates for wildflower appearance: