Milkweed (Asclepias spp.) plays a crucial role as the host plant for the monarch butterfly (Danaus plexippus), whose caterpillar feeds exclusively on it to further its development. The decline of milkweed populations due to habitat loss poses a significant threat to this species’ survival. The National Park Service aims to plant 100,000 native narrowleaf milkweed plants (Asclepias fascicularis) to combat this decline at Rancho Sierra Vista/ Satwiwa in California. A conservation strategy is to maximize milkweed plantings, yet increasing plant density can intensify intraspecific competition and impact species survival. This study focuses on how planting density influences narrowleaf milkweed growth. Using a randomized block design, 130 milkweeds were planted across varying planting density treatments ranging from control (1 plant per 1m² plot) to high density (6 plants per plot). Measurements were taken of both aboveground attributes (height, stem diameter, node count, leaf count, leaf length) and root characteristics (length, width, weight, count, grid count). Results indicate no significant variation in measurements among planting densities. However, final measurements were affected by the winter dormancy period. The statistical significance observed in leaf variables may have been influenced by the seasonal variation as well. Qualitative observations suggest seed propagation might be more advantageous over division propagation. Management practices should consider nurturing seedlings in a nursery for a longer time and clearing invasive species from planting sites to improve milkweed survival and support monarch conservation efforts.

Poster Presentation

Session 3

2:45pm – 4:00pm
Grand Salon

Environmental Science and Resource Management