Butterflies and milkweed

Tuesday, July 24, 2012

Scarlet milkweed, Asclepias curassavica, is a perennial sub-shrub from South America, yet because the caterpillars of Monarch and Queen butterflies are always chewing on the plants, they are sometimes even less than annual in my butterfly gardens. The leggy plants are about 2 to 3 feet tall with umbels of bright red/orange or yellow flowers. I’ve grown them in two different areas: on the east side of the house in a butterfly/bird garden without irrigation, and on the southwest side of the back yard, where, along with the rest of the yard, they are irrigated twice a week.

Caterpillar safe house.

Last year, the Monarchs found them right away, sipped nectar and laid their eggs. This year, several Queen butterflies, along with the Monarchs, are vying for a place at the table. After chewing the pointy leaves to nubbins, the caterpillars will eat the flowers as well as the thin stems. Some of the plants recover, but a few succumb to the pressure. A dry spring was hard on those in the area without irrigation.

Milkweed seedlings.

This summer, I decided to buy several containerized milkweeds, rotating one after another into a shade house so its seed pods could mature without being eaten. When we discovered scale on the leaves, milkweeds were banned from the orchid house. That was OK; the pods matured and I collected seed. To germinate them, I removed the silk that normally carries them on a breeze, soaked them in water four a couple of hours, then – following the procedure that Mary Collins uses for her nursery seeds – added a bit of bleach for a few minutes to ward off fungus. One more rinse and the flat seeds were planted just barely below the surface of the peat/perlite on June 30. They now are about 3 or 4 inches tall.

Jewel-like monarch pupae.

However, since last winter was so mild, the anoles were left unharmed and there are a gazillion of them in the garden. They have been eating the caterpillars as fast as the caterpillars can eat the milkweeds.

I bought a $20 butterfly-rearing house online, and last week installed a large three-gallon container of milkweed inside, complete with a few ½-inch monarch caterpillars. In a week’s time, and three milkweed plants later, four caterpillars have pupated and several more are approaching that size. The little green pupae, each with four golden spots, are hanging from the ceiling of the house like jewel cases. I’ve just returned from the nursery with more milkweeds as we wait for the butterflies and the seedlings to grow.

When supplies are tight, competition is strong.