Ask Mr. Smarty Plants

The common thread in this question is that you are asking about plants that are members of the parsley (carrot) family, Apiaceae , aka Umbeliferae. We need to clear up the confusion with plant identity because a couple of the plants are deadly poisonous. We also want to clarify the situation in regard to common names.

We are dealing with five different species of plants. Queen Anne’s Lace has the species name Daucus carota. In the case of hemlock, there is Poison Hemlock and Water Hemlock, both of which are highly toxic. There is also a hemlock tree, but it is completely unrelated. I could find no plant called cowslip parsley, but there is a Cow Parsley (plus image). There is a plant called Cowslip which is in the family Primulaceae, but we are concerned with the Apiaceae.

So we have four members of the family Apiaceae, two of which are quite toxic, that we would like to be able to distinguish using visual clues. Only three of the species occur in Marin County; Cow Parsley is the exception. The defining characteristic of this family is the inflorescence: a simple or compound umbel. According to spookspring.com , they are generally well known for being indistinguishable from each other, but identification is much easier than previously thought. Consider the plant’s habitat and size, then the presence or absence of bracts, and the shape and degree of dissection of the leaves; aroma is important too. This glossary will help you with some of the arcane terminology used by Botanists to describe plants.

Of the four, Queen Anne’s Lace is the easiest to distinguish. It has hairy stems up to one three feet tall. Poison Hemlock has smooth and waxy stems up to ten feet tall with purple or black spots, sometimes entirely purple. Water Hemlock has stems up to four feet tall that are smooth, waxy, and purplish at the nodes. Cow Parsley  has smooth waxy stems that are ribbed and grow up to five feet tall. Bracts beneath  the umbels and umblets is another distinguishing feature of Queen Anne’s Lace.

The leaves of Water Hemlock distinguish it from the others. They are bipinnate with the ultimate leaflets being lanceolate with serrate margins. The leaves of Poison Hemlock are comparatively huge, reaching up to 25 in. long and about as wide. They are bipinnate with the ultimate leaflets having deeply lobed margins (pinnatifid). The Poison Hemlock plant is also much larger (up to 10 ft. tall) than the others. The leaves of Queen Anne’s lace are smaller and and bipinnate. The leaflets are deeply lobed (pinnatifid). Cow parsley has leaves that are tripinnate with deeply lobed margins on the sub leaflets. It’s flowers have bracts beneath the umblets.

To Summarize:
 Poison Hemlock  is a tall plant, up to ten feet , that grows in disturbed areas. The stems have purple splotches, or may be completely purple. The leaves are large, up to 25 inches long and about as wide, and are singly pinnate. The ultimate leaflets have deeply lobed margins (pinnatifid).  Highly toxic!

Water Hemlock grows up to four feet in wet to moist areas. The stems are smooth with purple coloration at the leaf nodes. The leaves are bipinnate, and the ultimate leaflets are lanceolate with serrate margins. The leaves are distinct because they lack the multiple divisions and lobes found in the other three species. Highly toxic!

Cow Parsley grows up to five feet in sunny to shades ares in meadows and the edges of woodlands. The stems are smooth and ribbed .The leaves are tripinnate with deeply lobed margins on the sub leaflets. Said to be edible.

Queen Anne’s Lace grows up to three feet tall along roadsides, railroads, and in open fields. The stems are hairy. The leaves are bipinnately divided with pinnatifid leaflets. Possibly the ancestor to our modern carrot.

All of these species have white flowers that occur in an inflorescence called a compound umbel, and are very similar to the casual observer. In regard to flowers, the main distinguishing feature is that Queen Anne’s Lace has bracts beneath the umbels and the umblets, and Cow Parsley has bracts only beneath the umblets; The other two species lack bracts. In some instances, Queen Anne’s Lace has a single purple flower in the middle of the inflorescence.