Queen Anne’s Lace is in flower right now in Mid-July. Poison Hemlock is done flowering and is going to seed. So, the short answer is timing of flowers.
Queen Anne’s Lace, Daucus carota, also known as Wild Carrot, is in full flower along roadsides, pastures, and meadows. It has a white single flower and can be in clusters, but each flower is individual. Its flowers in early to mid-July, depending on the season.
A detailed description can be found here:
https://hort.extension.wisc.edu/articles/queen-annes-lace-daucus-carota/
Poison Hemlock, Conium maculatum, was in full flower in early June. It is now turning brown and going to seed.
Also, the sap of poison hemlock can cause heart problems when breathed and should not be mowed. Management of Poison Hemlock can be found at this link:
https://bygl.osu.edu/node/1763
The main difference is they flower at different times. The flowers are different as well.
Queen Anne’s lace flower:
Poison Hemlock flower:
The height of the plant is also different.
Queen Anne’s Lace is usually waist high, around 3 feet.
Poison Hemlock can get up to 6 feet or higher:
The stems are different as well.
Queen Anne’s lace has hair on it:
Poison Hemlock stem is green with pink blotches.
The flowers of each differ as well.
Queen Anne’s Lace has a single white flat-topped flower with a small pink center.
Poison Hemlock has a cluster of small white flowers, with multiple small white flowers making up a cluster of flowers.
The leaves are similar but differ slightly.
Queen Anne’s Lace Leaf:
Poison Hemlock Leaf:
From a distance, Queen Ann’s Lace and Poison Hemlock may look similar. But the flower timing is different. What you are seeing now in full flower in July in Northern Ohio is Queen Anne’s Lace.
