At the top of my driveway grows a white flower of unknown identity. Every summer when they start blossoming around the first of July, I make my way down the embankment through the grass, day lilies and bedstraws, take a couple of samples and pictures, and then head back to the house where the wildflower books are.

This summer, I did it all again, and I’m still not sure what the flower is. One thing I do know, though, is that I’m not going to eat it.

For a long time we called it Queen Anne’s lace, whose tiny white blossoms grow in an umbel shaped like a galaxy or a flat moon, just like the unknown flower. Queen Anne’s lace is also called bird’s nest because it curls up at night like a nest, as well as wild carrot because the root is like a small carrot and can be dug up, cooked and eaten. One local naturalist says that cultivating your Queen Anne’s lace will after some generations result in a larger root like a garden carrot.

But the umbel of the flower by my driveway is sparser than most Queen Anne’s lace, and it doesn’t have the tiny purple floret in the middle, as the wild carrot often does. You’d think this would be a helpful clue to identifying it. But you’d be wrong. There are several other flowers that look so much like these two that from a distance it’s hard to tell them apart. And up close, it turns out, some of them can kill you.

Like water hemlock. To the unpracticed eye, it looks like Queen Anne’s lace. But when you key it out with a book, you find differences. Water hemlock has a smooth, purple-streaked stem. Its umbels strongly resemble Queen Anne’s lace but tend — tend, mind you — to be more domed than flattened, and Queen Anne’s lace has a bristly stem and tiny leaflets called bracts hanging under the flowers, while water hemlock does not. The invisible difference is that water hemlock contains cicutoxin, which is a powerful neurotoxin.

In October 1992 two brothers, 23 and 39 years old, were searching in the woods of midcoast Maine for ginseng, whose blossom looks something like water hemlock. They apparently thought they might have found some because they both chewed into the root, the younger biting off more than the older.

“Within 30 minutes,” a Centers for Disease Control and Prevention report states, “the younger man vomited and began to have convulsions; they walked out of the woods, and approximately 30 minutes after the younger man became ill, they were able to telephone for emergency rescue services.

“Within 15 minutes of the call, emergency medical personnel arrived and found the younger man unresponsive and cyanotic with mild tachycardia, dilated pupils, and profuse salivation. Severe tonic-clonic seizures occurred and were followed by periods of apnea. He was intubated and transported to a local emergency department. Physicians performed gastric lavage and administered activated charcoal. His cardiac rhythm changed to ventricular fibrillation, and four resuscitative attempts were unsuccessful. He died approximately 3 hours after ingesting the root.”

Within a couple of hours the older brother was having seizures and delirium, but he lived.

The root they ate belonged to water hemlock, Cicuta maculata, aka spotted cowbane, which the CDC says killed five people in the U.S. from 1979 to 1988. And it could have been several other things, dangerous or not.

Ginseng looks less like water hemlock than do water parsnip, cow parsnip (aka hogweed), Scotch lovage, hemlock parsley and caraway, all of which grow around here, have edible parts, and look very much alike — which is to say not only like water hemlock, but also like bulb-bearing water hemlock and poison hemlock, both of which are also fatal to ingest.

In a range of resemblance to water hemlock roughly like that of ginseng are yarrow, whose feathery-looking little leaves are quick studies, and valerian, whose root can be turned into a sedative tea. I was attracted into a field by some lovely umbels that turned out to belong to, not valerian, but to a nice, healthy water hemlock. When I got up close I was pretty sure what it was but wanted to key it out in a book, so I broke it off at the ground where a few drops of sap fell out. I later learned even this was risky because the cicutoxin can be absorbed through your skin.

The flower at the top of my driveway has a grooved stem and is not mottled purple, so I’m pretty sure it is not water hemlock. It has characteristics of hemlock parsley, caraway and Queen Anne’s lace, but not all of any of them.

I’m sure someone can tell what it is, but it isn’t me, and I’m not going to test the root.