About Monarch Butterflies

In September and October, monarch butterflies will be laying their eggs on native milkweed using a combination of chemical and visual cues that have evolved over time. These beautiful and important pollinators have the most evolved migration pattern of any butterfly, and perhaps any known insect. They travel between 1,200 and 2,800 miles from North America to Mexico to hibernate.

Impacts

Invasive black and pale swallow-worts are members of the milkweed family and can be confused by female monarchs to be native milkweed. Monarch larvae that are mistakenly laid on swallow-wort will not survive. The threat of invasive swallow-wort is yet another blow to the Monarch population, that also faces challenges from climate change and loss of habitat.

How to Help

  • Introduce milkweed to your property (see videos below).
  • Search for and remove swallow-wort from your property (see details below).

Growing Milkweed

Harvesting and Planting Milkweed Seeds

Identifying Swallow-wort

Native to Ukraine, parts of Russia and the Mediterranean regions of Europe, black and pale swallow-wort were introduced as ornamental plants in the 1800s. They are perennial, herbaceous vines that grown dense stands that smother out understory vegetation and trees. Swallow-worts also release toxins into the soil that make it unsuitable for other plants to grow.

Learn More About Swallow-wort

Management Options

Prevention: Once established, swallow-wort is difficult to control. Monitor for populations in late summer, when the plants turn golden yellow and pods are present but not open. Stay out of infested areas during seed dispersal to prevent seed dissemination to unaffected areas. Likewise, clean your boots, ATVs, and other equipment when coming out of infested areas.
 
Initial control efforts should concentrate on plants in sunny areas since they will produce the most seeds.
 
Physical/Mechanical Control: Small patches can be dug out by hand. The entire plant must be removed and destroyed. To prevent seed dispersal, pods should be removed before they open and then burned. Large stands can be managed by consistent mowing when pods are very small (May-July). Controlled burning is not effective and may improve site conditions for swallow-wort seedling establishment.
 
Chemical Control: Triclopyr or glyphosate can be applied to foliage prior to seed set typically in late June to mid-July for the northern New York region. The use of surfactants helps herbicides penetrate the waxy leaf coating. Be sure to follow all instructions on chemical labels.