Milkweed, Monarchs, and Management- by Pam Johnson

Monarch on Milkweed

A Stewardship Committee member asked recently about planting milkweed in some of BHHT’s fields, to benefit monarch butterflies (Danaus plexippus). The question is a good one; the answer is not simple.

Stewardship obligations require, for the most part, that we maintain vegetation “as is,” with the exception of the removal of invasive plants noted in the management plans. Cutting brush and vegetation to create a new trail or maintain existing areas is also prescribed in management plans. Natural resources inventories for newly acquired lands help identify native plants, uncommon or not, that may be of management concern. A loop of Patten Stream’s trail was tweaked to avoid disturbing colonies of trailing arbutus, Epigaea repens, a beautiful woodland groundcover uncommon in Maine, but fairly abundant in our property there.

Specific intervention, that is, planting for wildlife benefit, has not yet been undertaken. Instead we have protected and stewarded habitats of high value to wildlife.

There are four milkweeds in Maine; common milkweed, Asclepias syriaca, is the most familiar, found in old fields and along roadsides. Milkweeds are nectaries and pollen plants for adult monarch butterflies; their leaves and stems provide food and shelter for monarch caterpillars. Maine is almost the northeastern end of the monarchs’ range. Most of the perils to the butterflies occur in their hibernacula in Mexico or along their migratory routes across the continental United States (deforestation, habitat loss, pesticide and herbicide use in industrial agriculture).

Before undertaking a costly and labor-intensive introduction of milkweed plants in our fields – broadcasting seed in unprepared ground is inefficient; well-rooted seedling plugs need some attention to insure they are not overrun by the highly competitive native and non-native plants of old fields – the best strategy is to locate and nurture existing milkweed populations. The field-mowing required on our fee lands can be delayed until autumn so that milkweed plants can mature and distribute their own voluminous seeds. Late mowing also allows adult monarchs to feed, and caterpillars to emerge. Hatch Cove in Castine has milkweeds, and mowing in September probably helped some monarchs embark upon their lengthy and miraculous life cycle.