Panel photo by Patrick Foote
Five of the "true" spring ephemeral species are found in
the rich hardwood forests & intervales of Nova Scotia
Photo-essay by JackPine (NSWFS)
Posted 4 Apr. 2012
The "true" spring ephemeralsThe "spring ephmeral" label is often applied rather loosely to all herbaceous species in eastern hardwood forests that flower before the tree canopy closes. It applies more properly to a "temporal guild" of herbaceous perennials that "emerge and senesce prior to canopy closure",1 i.e., whose above-ground parts, at least, are ephemeral.
These species have a small window of sunshine between snowmelt and leaf-out in which to grow, flower, be pollinated, and produce seeds. By mid-June the deciduous trees that tower above have cloaked the forest floor in deep shade. Spring ephemerals disappear in the heat of the summer, retreating underground until next year.2Sometimes this group is referred to as "the true spring ephemerals" to make the distinction from the more loosely applied term. The garden equivalents are the crocusses, daffodils, snowdrops, tulips and the like, which give us the first colour in spring but do not usurp the space for the summer flowers. They are all exotic to North America.
By my count, Nova Scotia has five species amongst the dozen or so cited in scientific papers as belonging to the spring ephemeral guild for the hardwood forests of eastern North America3:
Claytonia caroliniana (spring beauty)
at Cape Split, N.S. May 19, 2008
Dicentra cucullaria (Dutchman's breeches)
at Cape Split, N.S. May 18, 2008
Click on photos for larger versions/more photos.
More photos of spring ephemerals in Nova Scotia would be welcomed. Comments too!6
Cardamine diphylla (toothwort)
on Meander River, N.S.,
May 19, 2011
Erythronium americanum (trout lily)
by road at White Rock, N.S.
May 4th, 2011, photo by Patrick Foote.
|Some features of the spring ephemerals:7
The Early Summer ForbsMany more species belong to the temporal guild of "early summer forbs" or "summer greens" that emerge in spring and persist through canopy closure for varying lengths of time but reach peak coverage before mid summer. 1 As a group, these species grow to taller heights and encompass a wider range of growth forms and habitats than the spring ephemerals.9 Examples of the early summer species in the hardwood and mixed forests of Nova Scotia:
Some might ask whether Hepatica nobilis, one of the NSWFS favourites, fits in this scheme. Hepatica flowers early, but its leaves persist until the next spring bloom. Thus it is clearly not a spring ephemeral and because its leaves persist over winter, it differs from the early spring forbs defined as above. However, it would qualify as a "vernal herb" when that is defined simply as spring flowering herbs. See Hepatica, The Other First Flower of Spring for more about Hepatica.
Alliaria petiolata (garlic mustard)
in Victoria Park, Truro, N.S. May 23, 2009
Invasive vernal herb: garlic mustardGarlic mustard (Alliaria petiolata ) is a species of Eurasian origin that invades hardwood forests and outcompetes many of our native vernal herbs. It is a biennial, producing a basal rosette in its first year and flowering shoots in the second year. It is during the second year that it competes significantly with native species. The basal rosettes are capable of high rates of photosynthesis in the early spring while the canopy is open, enabling it to compete with spring ephemerals. Then,
…as the canopy closes and native [early spring and summer ] species begin to increase in cover and height, the elongating shoot of A. petiolata supports shade-adapted leaves at higher levels where they could more effectively compete with native species. Thus, A. petiolata grows in the early spring before most native species are actively growing, and extends its growing season into the summer through stem elongation and production of new leaves that are adapted to ambient irradiance levels unlike native ephemeral species or summer forbs. 11White-tailed deer are reported to "assist in its spread by eating native plant species that they prefer and are adapted to eat, leaving the garlic mustard behind." Garlic mustard was apparently introduced to North America in the 1800s for culinary and medicinal purposes.11 It is a relatively recent arrival in N.S., and found in only a few locales, so with some vigilance we could likely limit its spread and damage to native herbs.
Glossy and common buckthorns (Rhamnus frangula & Rhamnus cathartica) are also invasive in spring ephemeral habitats in Nova Scotia14
Conservation of our spring ephemeralsOf our five spring ephemerals, only wild leek is in imminent danger of being lost ("extirpated") from N.S. It is known from only a few locales in northern N.S. and is red listed (conservation status S1). The other four species are all ranked S4/S5. I suspect that that the longer term concern (indicated by S4) relates to the fact that the rich hardwood forests and intervales in which they occur were once widespread and extensive, but now are much smaller and highly fragmented, increasing the likelihood of progressive decline in abundance over longer time frames. These habitats are also under-represented in Nova Scotia's protected areas network.
Add to that, ongoing loss of these areas and threats from invasive species, clearcutting and excessive deer grazing, we should certainly not be complacent about the status of our true spring ephemerals. Hardwood intervales, in particular, are hotspots of plant biodiversity, and include threatened species such as blue cohosh and maidenhair fern, as well as the spring ephemerals. On the plus side, rich hardwood forests and intervales are amongst the sites currently being considered for addition to our protected areas network. Regardless we should never take these gems for granted!
Intervale forest on Meander River, N.S.
May 19, 2011