Over the past month Deborah and I have been closely watching the spring wildflowers in Harrison Hills Park. So far we have seen 40 different flowering species (a mix of native and introduced plants) and expect to see another 20 or so through the late spring and early summer. The “usual suspects” dominate almost every trail in the park: spring beauty, Jack-in-the-pulpit (left), Solomon’s Seal (both “true” and “false“), violets (at least 5 or 6 species of these!), mayapple, and skunk cabbage. There are also, though, some surprises like a large patch of Virginia bluebells (on the Pond Loop Trail), and red trillium (“wake robin”) in unexpected clusters along the woodland trails. We also saw many of our spring favorites including bloodroot, pepperroot, bluets, Canada mayflower and bellwort.
We have also watched many types of fern unfold from fiddle-head to expanded frond. Sensitive fern and New York fern joined the overwintering fronds of evergreen wood fern and Christmas fern, and both of these species began to grow their new fronds for the season. Large, circular bare patches between the trees filled in with thin fern stalks that will branch and thicken into a continuous, green cover over the coming weeks.
Mayapple is very abundant along almost all of the park trails. The distinctive “parasol” plant has thick, shiny green leaves and a partially hidden, nodding white flower. This perennial plant grows from expanding rhizomes and often forms large, interconnected patches of dozens to hundreds of genetically identical plants. Mayapple relies on soil fungi (mycorrhizae) to assist their uptake of soil nutrients. Competition with plants that inhibit these soil fungi (like garlic mustard) can be very harmful to mayapple. Reproduction in mayapple is via both vegetative growth (the expanding rhizomes) and via sexual reproduction (flowers that form fruit after pollination). There is a steep physiological cost involved in making flowers and fruit, and this cost can significantly drain the energy reserves from the colonial rhizome. This energy loss may even be sufficient to kill the large, clonal colony. Dispersal, though, of the species via the fruit, and the genetic mixing and variation that arises from sexual reproduction are advantages well paid for by this stress. In the masses of clonal mayapple along the park trails no more than 20 or 30% of the plants had the double leaf stalks with the forming flowers. The colonies seem to hedging their reproductive bets a bit!
Cherry saplings and pole trees along the trails are very numerous. The larger ones flowered weeks ago and most have dropped their white flower petals onto the brown leaf cover of the trails. Many of these cherry trees of all sizes are hosts for tent caterpillars. The dense webbing of the caterpillar masses fill in branch notches, and the incessant movement of the dark caterpillars is visible through the gray silk. Few other tree species are infested with these insects, and the abundance of these cherry trees is a good sign. A variety of birds especially the orioles and many warblers depend on these tent caterpillars to feed their nestlings. A seeming pestilence is a sign of plenty!
Crabapple trees in the understory are flowering along with the dogwoods. We even found a line of 10 or 12 young buckeye trees that were setting their distinctive white flower clusters. In the upper story the maples have all flowered and have begun to make (and are getting ready to drop) their winged samara, and the poplars and ashes have flowered and are now dealing with the serious business of leaf making. Even the oaks are starting to unfold their new leaves. The sky over the trails is getting more and more obscured by growing green of the tree leaves, and the sunlight reaching the forest floor is getting more and more diffuse.
The exotic invasive plant species are thriving along the Harrison Hills trails. Knotweed is up all over the park, garlic mustard (left) is in bloom, and the multifloral rose is thick and green. Along many trail sections multiflora rose is the dominant plant. In the trail sections where these invasive species are abundant, the diversity of the native species is noticeably reduced. Peering under the multiflora rose branches and looking in between the stalks of the knot weed we saw almost no other plant species. The allelopathic impact of the garlic mustard has already been mentioned, and its continuing impact on the soil fungi dependent plant species (including many wildflowers, shrubs, and trees) could become increasingly severe in the coming years. In nearby sites with fewer invasive species we were struck by the rich diversity and patch-complexity of the flora communities. We would see dozens of species of wildflowers from a single vantage point on these less stressed trails. We also saw some species that we have not yet found at Harrison Hills (including foam flower, rue anemone, wood anemone, and Bishop’s cap). In Harrison Hills, we saw diversity of wildflower species, but we often had to walk significant distances to see them due to the expanding homogeneity of the flora community.
There was, though, lots of things to see here. Patches of purple dead nettle (called “dead” because it does not make the “stinging” chemical of its fellow nettle species) and ground ivy form ideal habitats for American toads and garter snakes. We saw several, ten inch long, pencil thin garter snakes slithering through the ground cover to escape from our noisy footfalls and a number of bold, stoic toads that tolerated our presence.
It’s spring and going on to summer. One more Sign Of Spring blog to come. It is about the birds!