The monarch butterfly’s migration through PA has begun. How gardeners can help them

Cooler temperatures and shorter days; goldenrods and asters blooming by the roadside. These are all unmistakable signs that the monarch butterfly’s migration through Pennsylvania has begun! Even those who aren’t especially interested in the natural world are captivated by the bright colors and epic journey of the monarch butterfly (Danaus plexippus). And for gardeners, who know the importance of pollinators, it’s even more compelling news.

Many are aware of the importance of milkweed as a food source for monarch caterpillars, who dine exclusively on this plant. The nectar is also a valuable resource for adult monarchs. But in September, migrating monarchs rely on fall-blooming natives such as rudbeckia, goldenrod and asters to supply the energy they need to complete their flight. Streaming down from as far north as Canada, the monarchs we see in Pennsylvania could be traveling as far as 3,000 miles to reach their winter homes in the Oyamel fir forests of Mexico.

Not only do monarchs need plenty of fuel for the trip, but they also require plenty of fat reserves to see them through the winter. The “summer” monarchs we observe from April through August live for about four weeks, searching for nectar, mating and laying eggs. But the so-called “super” or “Methuselah” generation — those that will head to Mexico — behave differently. Unlike their parents and grandparents, these butterflies aren’t interested in reproduction. Their entire focus is on tanking up for the journey ahead, and they’ll need every bit of energy they can store, as they’ll live up to eight times longer than summer generations.

Because of their very purposeful feeding, gardeners can often get quite close to observe monarchs at this time of year. You may have spotted quite a few of these beautiful migrants this September; local observers have noted a higher-than-normal population. According to monarch researcher Karen Oberhauser of Monarch Joint Venture, this reflects a trend throughout the entire eastern part of the monarch’s range, with relatively high numbers compared to the last several years.

So, how can a gardener help these intrepid pollinators on their way? Obviously, planting milkweed (Asclepias spp) so that they can reproduce is an important first step. In our area, there are five native species, including swamp milkweed (A. incarnata), common milkweed (A. syriaca) and butterfly weed (A. tuberosa). All feature the distinctive milky sap and sweet nectar that make them uniquely adapted for a monarch’s needs. As the name suggests, swamp milkweed is best suited for moist to wet areas, while common milkweed will thrive just about anywhere.

In addition, adding fall-blooming native plants such as the stately New England aster (Symphyotrichum novae-angliae) or the more compact aromatic aster (Symphyotrichum oblongifolium) will provide a plentiful nectar supply for all pollinators, including the famous migrators. Planted alongside one of the many species of goldenrod (Solidago spp), the mix of purple and gold is a winning combination for both gardener and pollinator. We can all help monarchs to a successful journey’s end!

If you’d like to experience monarch tagging first-hand, mark your calendar for Saturday, Sept. 20 at 2 p.m. at the Snetsinger Butterfly Garden in Tudek Park. In partnership with Monarch Watch, Master Gardeners of the SBG will tag and release migrating monarchs, contributing to scientific research that helps researchers understand migration patterns, survival rates, and the many challenges monarchs face. More information can be found at snetsingerbutterflygarden.org.

In the garden this month:

• Plant now for spring blooms! Bulbs such as crocus, daffodil, narcissus and tulips can all be planted now. 

• Sow quick-growing, cool-weather favorites such as lettuce, spinach, kale and radishes for a last harvest before frost

• September is a great time to plant trees and shrubs; be sure to keep them well-watered until the ground freezes — even if temperatures are cool.

• Bring in houseplants that have been summering outdoors. Give them a good blast of water all over before bringing them in to help remove any hitchhiking insects.

• Bring in houseplants that have been summering outdoors. Give them a good blast of water all over before bringing them in to help remove any hitchhiking insects.

• Fall is the best time to test your soil and make any amendments needed. You can find soil tests and submission guidelines here: agsci.psu.edu/aasl/soil-testing/fertility.

Lisa Schneider has been a Master Gardener volunteer since moving to PA in 2017. Have a home gardening question? Email CentreMG@psu.edu.