PLANT SCOUT HOW TO GET YOUR GARDEN FULL OF BUTTERFLIES.
Many a gardener knows that milkweeds (Asclepias) are host plants for Monarch butterflies. This means that adults lay their eggs in the foliage of these plants, the caterpillars hatch, start feasting on the leaves to grow and fatten, and then at some point spin themselves a chrysalis from which eventually emerges an adult butterfly. What may not be as well known are the factors underlying these instinctual decisions. Each species of butterfly has one or more host plant that they choose over all others on which to lay their eggs and begin this cycle.
These choices have to do with the specific botanical nature of the host plants, their location and when they flower, especially if this involves migration. In the case of Monarchs, an important reason for choosing Asclepias as their host plant is that the leaves contain a milky sap, consisting of a latex containing toxic alkaloids. The caterpillars are unharmed, but any predator eating them gets a nasty surprise. Monarch caterpillars advertise this toxicity by being brightly colored.
Gardeners can do their part in helping the local butterfly population by planting a number of common and commercially available plants in their garden. Though you may choose a particular plant as a host plant, rest assured that other species of butterflies will likely come calling for the nectar these flowers provide.
It is advised to use either of the two native milkweeds (A. fascicularis and A. speciosa) to avoid potential issues with parasites. (See article online here: http://bit.ly/2mtAu6o)