HACKENSACK, N.J. – Plant some milkweed in your yard this year – and you can help save the monarch butterfly.
Monarch butterflies, well-known for their unique migration from across the United States down to Mexico each fall, have been in decline for years, and are at the lowest numbers scientists have seen in the several decades they have been tracking them.
The easily identifiable orange-and-black monarchs have been hit hard by a number of factors, but perhaps most devastating is the loss of the one species of plant the monarch lays its eggs on – milkweed.
As a result, the Audubon Society is asking residents to plant milkweed in their gardens and for highway road crews and parks groundskeepers to avoid cutting milkweed that grows wild along roads and in open spaces. Bergen Audubon is also donating milkweed plants to schools and community gardens.
“We’re trying to do what we can to help,” said Don Torino, Bergen Audubon’s president. “Some environmental issues seem so big and overwhelming, and people feel powerless. But here’s something simple they can do to help.”
Milkweed is essential to monarchs because it is the only plant that the butterfly species lays eggs on – and which the monarch caterpillar can eat.
“To a butterfly, the typical suburban yard with rhododendrons, non-native Norway spruce and lawns with non-native grasses might as well be a movie set – there’s no reality to it for them,” said Jeffrey Glassberg, president of the Morristown, N.J.,-based North American Butterfly Association.
Monarchs migrate south each fall to fir forests in the mountains of central Mexico, where they spend the winter. In the spring, they migrate north and spread throughout the United States.
The generation that spends the winter in Mexico can make it back north as far as Texas, and lay its eggs on milkweed plants. Within four days, the eggs hatch into yellow-white-and-black-striped caterpillars, which eat the host plant’s leaves. After two weeks, the caterpillar attaches to the underside of a branch or leaf and becomes a chrysalis. Ten days later, after metamorphosis, the full-grown monarch emerges and continues the migration north. Monarchs will go through four generations of butterflies during the spring and summer migration process.
But several factors have disrupted the traditional migration and reduced the monarch numbers, Glassberg said.
There has long been illegal logging in the monarch wintering grounds, and some extreme weather – droughts in Texas, extreme cold elsewhere – have also hit hard in recent years.
But perhaps the most significant factor has been the loss of milkweed plants as large-scale commercialized farms have used herbicide around fields. The herbicide kills weeds around the farmland – including wildflowers and milkweed. Without milkweed, the monarchs have no place to lay eggs, and their caterpillars have no food source.
In addition, during the migration season, monarchs rely on milkweed and other wildflowers for the nectar they turn into sugars to help fuel their journey. Herbicides have also knocked out swaths of wildflowers, cutting the monarchs’ nectar supply, Glassberg said.
The common milkweed, which grows in empty lots and along roads and fields, “is not very attractive – it grows to three feet and looks very weedy and has big leaves. It tends to get cut down,” said Janice Mahr, who grows perennials for Metropolitan Plant and Flower Exchange in Fort Lee and Paramus.
Most nurseries carry two types of milkweed that have been cultivated to look better in gardens, she said. The cultivated versions are asclepias tuberose, or butterfly weed, which has round masses of tiny bright orange flowers, and asclepias incarnata, or swamp milkweed, which comes with white or pink flowers.
Mahr has seen increasing interest among customers who want to plant milkweed in residential gardens. Her nurseries are starting to stock these varieties now and more will be coming later, since they were slowed by the cold early growing season.
Glassberg said monarchs are not the only butterfly to rely on a single plant species to lay eggs and provide food for their caterpillars. There are 139 different butterfly species found in New Jersey. For instance, wild blue indigo, or false indigo, a perennial, is a caterpillar food for the orange sulphur, clouded sulphur, frosted elfin, hoary edge skipper, wild indigo duskywing and eastern tailed-blue butterfly species. The New England aster, another perennial, is caterpillar food for the pearl crescent. Some shrubs and trees also serve as caterpillar food.