Monarch Watch provides information on rearing monarchs and their host plants.[8] Efforts to restore falling monarch butterfly populations by establishing butterfly gardens and monarch migratory "waystations" require particular attention to the target species' food preferences and population cycles, as well to the conditions needed to propagate and maintain their food plants.[9]
For example, where it grows in the southern Great Plains and in the western United States, monarchs reproduce on A. viridis, especially when its foliage is soft and fresh. Because monarch reproduction peaks in those areas in late summer and early fall when scenescent milkweed foliage is old and tough, A. viridis needs to be mowed or cut back in July to assure that it will be regrowing rapidly when monarch reproduction reaches its peak.[10]
A. virdis is one of the first milkweeds to bloom in the Ohio River Valley (May to June). In that area, monarch butterfly and milkweed tussock moth (Euchaetes egle) caterpillars are seldom found on the plant as it sheds its leaves and becomes dormant in late June to early July before the two Lepidoptera species arrive.[3]
Cultivation
The plant is difficult to cultivate and does not grow well in containers.[11][12] The seeds of some milkweeds need periods of cold treatment (cold stratification) before they will germinate.[13] To protect seeds from washing away during heavy rains and from seed–eating birds, one can cover the seeds with a light fabric or with an 0.5 in (13 mm) layer of straw mulch.[14] However, mulch acts as an insulator. Thicker layers of mulch can prevent seeds from germinating if they prevent soil temperatures from rising enough when winter ends. Further, few seedlings can push through a thick layer of mulch.[15]
References
^NatureServe (December 1, 2023). "Asclepias viridis". NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer. Arlington, Virginia: NatureServe. Retrieved December 17, 2023.
^National Academies of Sciences, Engineering, and Medicine (2020). Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies. Washington, D.C.: National Academies Press. pp. 79–80. doi:10.17226/25693. ISBN9780309481328. LCCN2020935714. OCLC1229163481. S2CID218854539. National Cooperative Highway Research Program (NCHRP) Research Report 942. Archived from the original on July 29, 2020. Retrieved July 8, 2021. Could roadside mowing stimulate milkweed growth and support monarch breeding? Limited research in eastern North America has shown that spring or summer mowing can promote new growth and extend the availability of milkweed plants for monarch breeding. Mowing may stimulate growth of some milkweed species, particularly those that spread through rhizomes like common milkweed (A. syriaca) and showy milkweed (A. speciosa). Summer (June or July) mowing in Michigan resulted in more monarch eggs on regenerated stems than unmowed stems. Summer (July) mowing and burning can increase green antelopehorn milkweed (A. viridis) availability in the late summer and early fall in the Southern Great Plains, whereas in areas without mowing, the milkweed has senesced by August. In the West, showy milkweed will regrow after summer mowing and continue to support monarch breeding (Stephanie McKnight, personal observation). However, more research is needed in other areas to determine the optimal timing and frequency of mowing that promotes not only milkweed but also nectar plants. It is also unknown if the benefit of additional milkweed availability in the fall outweighs the costs of the larval mortality caused by summer mowing. The benefits are likely greater in areas that primarily have breeding monarchs in the spring and fall and where the dominant species of milkweed spread by rhizomes. Sources: Alcock et al. 2016; Baum and Mueller, 2015; Bhowick 1994; Haan and Landis 2019; Fischer et al. 2015
^(1) Borders, Brianna; Lee-Mäder, Eric (2014). "Milkweed Propagation and Seed Production: Stratification"(PDF). Milkweeds: A Conservation Practitioner's Guide: Plant Ecology, Seed Production Methods, and Habitat Restoration Opportunities. Portland, Oregon: The Xerces Society for Invertebrate Conservation. pp. 28–29. Archived(PDF) from the original on July 4, 2021. Retrieved July 12, 2021. (2) Landis, Thomas D.; Dumroese, R. Kasten (2015). "Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat"(PDF). International Plant Propagators' Society, Combined Proceedings (2014). 64: 302. Archived(PDF) from the original on March 8, 2021. Retrieved July 11, 2021 – via United States Department of Agriculture: United States Forest Service. Many sources of milkweed seeds require stratification (cold, moist treatment) before sowing. In a review of stratification requirements for common milkweed, recommendations varied from as short as 7 days to as long as 11 months at 5°C (41°F) (Luna and Dumroese, 2013). Butterfly milkweed (A. tuberosa) germination increased from 29 to 48 to 62% as stratification duration increased from 0 to 30 to 60 days, respectively (Bir, 1986). Our informal natural stratification trial with showy (milkweed) and narrow leaf milkweed (A. fascicularis) in southern Oregon revealed that seeds began to germinate after 15 weeks in stratification (Fig. 3A). (3) Higgins, Adrian (May 27, 2015). "7 milkweed varieties and where to find them". Home & Garden. The Washington Post. Archived from the original on September 26, 2020. Retrieved October 17, 2020. Seed may be stubborn to germinate and may need a period of cold treatment..
