Notice! Mark your calendars for the “Autumn Equinox Party” at the Teaching Garden, Friday September 22, from 6:30-8:30. Bring a finger food to share. Beverages provided. Violinist, Michael Francis Harvey and Capital Naturalist, Alonso Albuegattas will be there. Please RSVP at Horticulture Help Desk 703.792.7747 or firstname.lastname@example.org
We all look forward to the cooler temperatures of autumn and it is exciting to see these changes in our gardens! Driving out into Fauquier and Loudoun counties we can already see maples starting to change color, and the hay fields are a beautiful crimson color. Thistle, aster, goldenrod and sunflowers can be seen along the roadsides as well as ripening fruit of sumac. All the walnut trees in Middleburg seem to be covered in fall cankerworm!
Depending on the local weather, we can often see these changes in the beginning of August. This year, we did not experience the drought conditions often seen in our area in late summer, so changes we are seeing are probably due to the change in daylight (actually, night time) hours. High pressure, continental air masses have been sweeping down from Canada bringing us the cooler and drier days, with fair weather cumulus clouds. These changes in temperature trigger senescence and dormancy. Insects and animals also detect these changes, and prepare by storing energy for the winter or migrating.
Some of the signs I have been noticing for a week on my walks are the gradual break down of chlorophyll in sassafras, poison ivy, and Redbud. Chlorophyll a and b start to break down, leaving red (anthocyanin), yellows (xanthophyll) and orange (carotene) pigments. These pigments gather light at different wavelengths to make that last bit of carbohydrate for the plant. My woods are filled with the sounds of dropping pignuts, black walnuts, and acorns, and squirrels are busy burying them in the middle of the yard. The young neighborhood bucks are still hanging out together and the velvet on their antlers is noticeable. I have noticed the hummingbirds are particularly competitive at the feeder, trying to store as much energy as they can before migrating. Sumac, wild grape and pokeweed berries are ripening and the annual return of ragweed is in full force.
The Teaching Garden is also showing lots of changes. The Echinacea in the beds have gone to seed and died back. Switch grass is beginning to turn red and Amsonia is starting to turn yellow. The Woodlands dogwood leaves are changing color, they are setting fruit and the Nachez Crepe Myrtle is peeling, and also setting fruit. In the the Woodlands, Toad lily is now blooming, as well as Ligularia.
The Master Gardeners have been sending lots of pictures of Arachnids and insects getting ready for fall. One of the most intriguing Arachnids has taken up residence in the drought tolerant bed, the Yellow Garden spider (Argiope aurantia). These spiders are active in late summer and early fall. Known for their large web up to 2 ft across, early fall is the time of year when the female mates and then eats the male. The spider’s eggs overwinter and spiderlings hatch in the spring. Her large, circular web has a characteristic vertical, zigzag shaped “stabillmentum” in the center. A nightly ritual is to consume the circular center and rebuild it each morning with fresh silk. This spider is non-aggressive, rarely finds her way indoors (by accident) and prefers garden areas.
The gardeners have also seen an increase in adult Praying Mantis getting ready to deposit their eggs in a frothy secretion that hardens into a case. These cases are attached to twigs, leaves and fences and stay protected from predators and severe winter weather until spring.
We have also seen many butterflies this summer, and many of the gardens have milkweed for the Monarchs. Monarchs begin their annual migration in August from all over North America, to Mexico to overwinter. Some scientists believe this migration may be as old as 10,000 years, beginning around the end of the last glacial period. The earliest reports recorded are from the 1860’s, in California. Monarchs will only lay their eggs on milkweed, and during breeding season, will have up to 4 broods. The largest population is found in the fall, when they are getting ready to migrate. This migratory generation are the great, great grandchildren of the ones that left Mexico last spring. In Mexico, they cluster in a 2 acre area in the mountainous Oyamel fir forests, where they are bathed in moisture from fog and clouds. In the Bee, Bird, and Hummingbird garden, Teri Madden tells me that she is still seeing adults and caterpillars. By the road side, Milkweed bugs are also feeding. Not harmful to Monarchs, they do compete for resources. If you see them in your Milkweed garden, just pick them off and give them a swim in the “swimming pool”. Never spray pesticides!
A few of the gardeners have seen Woolly Bear and Blonde caterpillars already. Folklore has it that the ratio of black to red on the Banded Woolly bear (Pyrrharctia isabella) is an indicator of the severity of the upcoming winter. There has actually been some scientific studies to correlate these two things that found (maybe) some evidence, but for now, its mainly considered an old wive’s tale. We do see more of them this time of year because they overwinter as a larva, and go searching for protected sites under bark or inside cavities of rocks and logs. They can be seen traveling pretty fast to get across the road!
Whatever your favorite things about fall are, its always fun to mark these changes every year! Some see the back to school supplies in the middle of summer, the yellow buses practicing their routes, pumpkin lattes offered at coffee shops, mums, pick your own apples, or the last episode of Game of Thrones. Master Gardeners celebrate the (almost) end of weeding, (especially Japanese Stiltgrass), squash and vine ripe tomatoes, and planning for our next years gardens! Happy fall everyone!