What is MilkweedWatch?

The MilkweedWatch program asks members of the public to assist researchers and citizen groups concerned with the health of monarch butterfly populations by identifying the location of milkweed plants, which are crucial for monarch reproduction in Canada. The data you submit will assist in the monitoring of the presence and abundance of milkweed, and help researchers and conservation groups protect, preserve and foster milkweed across Canada. Your observations make a difference!

Why watch for milkweed plants?

Milkweed plants are the primary source of food for caterpillars of the monarch butterfly (Danaus plexippus). The monarch is easily Canada’s most recognizable butterfly, and can be found each summer in the southern areas of every Canadian province. Adult butterflies lay their eggs on the underside of milkweed leaves. Within a week, caterpillars hatch from the egg and feed on the milkweed leaves for approximately two weeks. The caterpillar then hangs upside down from a leaf, attached by a silk thread, and forms a chrysalis, inside which it will pupate (i.e. transform into a butterfly). The adult butterfly emerges within two weeks, and will repeat the reproductive cycle. As autumn approaches, adult monarchs migrate south to the US and Mexico, where they spend the winter and reproduce.

The milkweed plant is the key to the monarch’s success. Milkweeds come in over 150 different types, but share a common trait of being mildly toxic. Most animals avoid eating milkweed, but the monarch caterpillar is able to do so safely. Because it eats milkweed, the caterpillars ingest and accumulate the milkweed’s toxins, making both the caterpillar and the adult less palatable to birds and other predators.

North America’s monarch populations have declined in recent decades. This decline is attributable to a variety of factors, including habitat loss in the monarchs’ overwintering areas, declining availability of wildflowers in Canada and the US, parasites, and pesticides. Another important factor is a decline in milkweed in many parts of North America where herbicides are used on agricultural fields. We must maintain a healthy milkweed population in Canada, which provides an important buffer against future monarch population losses.

Your help is needed

Help scientists and conservation groups monitor, protect and grow Canada’s milkweed population by recording in Milkweed Watch where milkweed is found. It’s easy to do. Using your smartphone or home computer, record any locations you find milkweed, in your yard, neighbourhood or local park, on farmland or at roadsides. Milkweeds are easy to identify, and there are only five species commonly found in Canada. While there, look and see if there are any butterflies and, gently, check leaves for caterpillars, eggs or chrysalises. You can record these, too, in MilkweedWatch.

Ready to watch for Milkweed?