Successfully storing milkweed taproots for habitat restoration

Abstract

During a 3-y seed increase project, taproot size (volume and biomass) of showy milkweed (Asclepias speciosa Torr. [Asclepiadaceae]) increased annually, although top diameter of the taproot remained constant after the first growing season. At the end of the third year, taproots were harvested, held under different cold storage treatments, and subsequently outplanted. We observed that taproots can readily be stored in cardboard boxes placed in either cooler (0.5 to 2 °C [33–36 °F]) or freezer (−5 to −2 °C [23–28 °F]) conditions, and that success increases with the addition of protection from the cold in the form of plastic bag liners and (or) peat moss; survival was as high as 90%. These findings are promising because milkweeds are essential to the life cycle of the monarch butterfly (Danaus plexip pus L. [Lepidoptera: Nymphalidae]), which has experienced large population declines during the past 20 y due primarily to habitat loss and fragmentation. Restoring milkweed to the environment is an important first step to help bolster populations. Seed increase is often used to produce seeds for specific restoration projects, but the taproots are often discarded once sufficient seeds have been attained. Harvesting the taproots is an effective way to efficiently use all parts of the increase bed. By utilizing cold storage, milkweed taproots can be harvested, stored, and outplanted at the proper time to produce viable and prolific plants for further restoration work and monarch habitat rehabilitation.