Grow milkweeds to help save the monarchs

Many people are interested in helping monarch butterflies. The number of migratory western monarchs that return to their overwintering sites in coastal California fluctuate each year, according to the Xerces Society for Pollination Conservation. But the population generally represents a fraction of the millions present until about the 1990s.

There has been some recent controversy about what milkweed to plant for monarchs. Milkweed is where the adult butterflies lay their eggs and it is food for the caterpillars.

There are compelling reasons for planting native species of milkweed. They are very drought resistant and have adapted to local soils and climate.

I first became acquainted with native milkweeds when I noticed some growing on our newly acquired, almost bare 1-acre piece of property in 1990. My 3-year-old son spotted fat green caterpillars devouring the leaves of a small patch of native woollypod milkweed — Asclepias eriocarpa — in our yard and became transfixed.

We visited the patch daily, watching the caterpillars grow while the leaves diminished. To my son’s eyes they magically transformed into an emerald-green, gold-bejeweled chrysalis and then into a vividly hued butterfly slowly drying in the sun to fly away into the future. Seeing the process of metamorphosis through a child’s eyes is a very special thing, but I think I was no less affected and have planted milkweed in every garden since.

Getting to know this small patch of milkweed and its essential function in supporting monarch caterpillars made me focus on what other native naturally occurring milkweeds were growing in the immediate neighborhood. In our neighbor’s sheep pasture, there were a number of woollypod milkweed patches, and despite the pasture being grazed to the ground, the sheep, Navajo churros, didn’t touch them.

Other varieties spotted in the landscape

There were also a number of the plants in a nearby vineyard. The narrowleaf milkweed, Asclepias fascicularis, a much less showy species and one more tolerant of poorly drained conditions grew on fence lines. On hillsides in the spring, heart leaf milkweed — Asclepias cordifolia — bloomed with the wildflowers. It had showy, striking reddish stalks and blooms rising singly in a still quiet landscape. It disappeared and went dormant in the summer. On roadsides in neighboring Lake County, I saw the striking architectural forms of the showy milkweed, Asclepias speciosa.

There is a right milkweed for every garden and each situation. The longest blooming (sometimes all summer), and seemingly best for pollinators and beneficial insects is the narrowleaf milkweed. It can tolerate heavier soil than most. The green, narrow leaves and small pink-and-white flowers don’t jump out in the landscape, but bees, other pollinators, beneficial insects and monarchs will surely find it.

This milkweed grows easily in our gardens. With regular water and fertile soil it can really spread. The best place to grow it is in areas out of flower beds that receive regular irrigation. It is 2 to 3 feet tall.

The most widely grown native milkweed is the showy milkweed. Very large, pink-white, showy flower clusters are held aloft on top of striking stalks of large gray, oval leaves. Showy milkweed has strong upright growth, is very drought resistant or can tolerate some irrigation. It will spread slightly to form a patch but doesn’t overwhelm. Unwanted shoots are easily pulled. It grows in many soil types and over much of the western U.S. Butterflies gather nectar on its blooms and pollinators visit the flowers. The excellent selection “Davis” has fancy, fragrant white flowers and the leaves are a striking white. It is about 2 to 3 feet tall.

Another native milkweed found in drier valley floors and hills is the woollypod milkweed. This is a very beautiful plant, with almost white oval leaves, and beautiful large round umbels of white flowers. The whole plant may only be a foot tall. It is not invasive, but very slowly forms widely spaced colonies over time. Unfortunately, this milkweed is difficult to find as a plant. Only a few nurseries, like Larner’s Seeds in Bolinas have seeds. Likewise, the heart leaf milkweed is almost impossible to find as a plant or seed.

Aphids attack

Many milkweed plants are plagued with orange oleander aphids in summer. This is a nonnative aphid that is able to tolerate the toxins found in the plant. As the aphids secrete honeydew, mold can form, turning older plants into a sticky mess. An easy strategy to manage them is to have two patches of milkweed. When the aphids appear, cut one of the patches that has declined down to a couple inches from the ground. When leaves regrow, cut down the original patch.

New growth is apparently not as attractive to the aphids. Keep an eye out for caterpillars or eggs. Transfer them to healthy foliage if you see them on plants that will be cut down. Fresh, young milkweed foliage will be in prime condition for southbound migrating butterflies in late summer. The monarch butterflies’ southern migration begins in August and lasts into early October.

Kate Frey’s column appears every other week in Sonoma Home. Contact Kate at: katebfrey@gmail.com, freygardens.com, Twitter @katebfrey, Instagram @americangardenschool.