Arboretum visitors are not the only ones enjoying this week’s early spring sunshine. Across the grounds, swaths of colorful spring ephemerals have poked their parts above the soil to take advantage of unobstructed access to sunlight. These perennial woodland wildflowers produce stems, leaves and flowers well before the leafing-out of woody understory and canopy species. After completing their reproductive cycles, spring ephemerals wither away, spending the remainder of the year underground as roots, bulbs and rhizomes. This reproductive strategy, relying on a rapid phenological response to sunlight and rising soil temperatures, allows diminutive (albeit striking) herbaceous species to persist even in dense, shady woodlands.
Throughout the collections, visitors can expect to see a variety of vibrant spring ephemerals over the next few weeks. Many, such as the splendid blue Siberian squill (Scilla siberica), came to the United States as introduced ornamental species. Snowdrop (Galanthus nivalis), cloaked in bright white, emerges late in winter and is naturalized throughout much of southern New England. Another European native and harbinger of spring, the giant crocus (Crocus vernus), appears on the Arboretum’s grounds in both a royal purple and a striking white. Lesser celandine (Ficaria verna), a sunny but less-than-celebrated invasive perennial, proliferates through its rapid reproductive cycle, forming dense mats and crowding out vulnerable native ephemerals.
The keen explorer will often find these native ephemerals in moist, protected areas of the Arboretum. Along Bussey Brook, skunk cabbage (Symplocarpus foetidus) grows discretely, its alien blossoms hidden among the grasses and sedges. In addition to its noxious scent and other odd qualities, skunk cabbage is notable for its ability to raise internal temperatures and emerge even through spring snow. Another ephemeral with a unique talent, the dogtooth violet (Erythronium dens-canis), produces seeds that ants find irresistible. By transporting these nutrient-coated seeds to feed growing colonies, ants provide both a means of dispersal and measure of protection for the plant’s progeny.
The phenology of spring ephemerals has long been a topic of interest among naturalists and thinkers of the Northeast. From 1852 to 1858, Henry David Thoreau, the celebrated New England transcendentalist, recorded phenological observations of the many (over 500!) herbaceous and woody species surrounding his home at Walden Pond in Concord, MA. 150 years later, biologists have used Thoreau’s data set to study the changing climate of New England and how these changes have likely affected local species diversity.
The emergence of spring ephemerals reminds us of the value of our Arboretum, as a place of deep natural beauty and as a grounds for scientific observation and inquiry. Both aspects of the institutions are captured below, in a glass plate negative made by plant collector and photographer Ernest Henry Wilson, showing a patch of Siberian squill on the slopes of the Bussey Institute. With a little imagination, we can picture the brilliant blues that caught Wilson’s eye and caused him to pause on a bright spring day.
Siberian Squill (Scilla siberica) on the grounds of the Bussey Institute. Photographer: Ernest Henry Wilson [ca. 1919–1930] Click here for more of Wilson’s photography.
If you’re interested in learning more about phenology, botany, or ecology, join the Arnold Aboretum Tree Spotters, a group of citizen scientists who collect data from 11 species throughout the Arboretum to assist studies focused on plant responses to climate change. Read more about Tree Spotters in Silva [pdf].