Now that the green season has taken hold and a handful of wildflowers are blooming, it's time again to break out Newcomb's Wildflower Guide. I noticed a plant with tiny (<1/4") white flowers last week in Wells and was pretty sure I knew who I'd found. Keying out the plant confirmed my hunch.
I began by determining the plant's 3-digit code:
Flower type: 4 Regular Parts (4--)
Plant type: Wildflowers with Alternate leaves (43-)
Leaf type: Leaves Toothed or Lobed (433)*
Then, on page 4, under group 433, the key asked if the flowers were yellow (no) or white, pink, or purple (yes), and if the leaves had an arrow-shaped base, which clasped the stem (yes, though this is not well depicted in my photos) or were not arrow-shaped (no). The key then pointed to page 136.
Of the six plants described on that page, only one description fit my mystery plant. Basal leaves deeply lobed; pods triangular (to me the pods are triangular/heart-shaped). A drawing of the plant on page 150 provided visual confirmation. The plant I'd located was Capsella bursa-pastoris, known as Shepherd's-purse, a member of the Mustard (Brassicaceae) family.
Shepherd's-purse is a widespread, weedy species who typically grows in disturbed soil in full sun. The flowers, immature seed pods, and tender leaves and shoots are edible, especially for those who enjoy a spicy mustard flavor (boiling can reduce the flavor, if desired). The mature pods can also be used as a spice. Arthur Haines documents many medicinal uses for this herbaceous annual in Ancestral Plants (Vol. 2, 2015, p. 126-27). You can find more photos of Shepherd's-purse at GoBotany.
To view the following images in full-size, click here.
*Note: Looking at the basal leaves (instead of the stem leaves), you might wonder whether they're considered divided or toothed/lobed. Newcomb's guide accounts for this confusion by directing you to Shepherd's-purse whether you choose the former or the latter.