Wednesday, May 1, 2013

Spring ephemeral a day - Bloodroot

What: Look for bloodroot in hardwood forests enriched by calcium-rich bedrock. The flowers are variable, but generally have 8 petals, and can have up to 20 or so, though I usually see them in the 8-10 range.

The leaves come up first, cupped around a flower bud.l The flower opens first as the leaf begins to unfurl. I got to the spot around 3pm, but got distracted by a pair of deer. I followed the deer for a few hours and when I got back I noticed that many of the flowers that had previously been opened began to close up. 

Turns out bloodroot flowers are indeed nyctinasitc (flowers that open during the day and close at night; from nycto: nigth + nastic: non-directional response to external stimulus). My initial suspicion for why plants do this is that they might be selectively pollinated by a specific diurnal pollinator (but the flowers don't appear very specialized for this) or that it could protect the flower's reproductive parts from the cold night temperatures of the early spring woods. I found another proposed theory that points to weather as well, but a different threat. With temperatures so high during the day and cold at night, the temperature swing means lots of dew in the morning. If the stamens - where all that pollen is - get wet from the dew, then pollen the pollen won't transfer as well to insects.

Seedlings sprouting up. These first year plants won't develop flowers.
Where: Centennial Woods, as far as I know there is only one place in Centennial Woods with a bedrock exposure (down the slope on the southeast corner of the hospital commuter parking lot at the end of Carrigan Dr). The bedrock is Winooski Dolostone (dolostone is also called magnesian limestone), which has a higher concentration of calcium. So in that little plot there's an excessive amount of bloodroot, which is found nowhere else in those woods.

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