Hi Debby,

I have been seeing quite a bit of poison hemlock this spring.  It is getting close to knee high in several patches.  Now is a good time to get rid of it.  One of the easiest and most effective ways would be with the use of a herbicide.  Herbicides typically have little or no direct impact on bees.  Insecticides are the real concern with pollinators.  Using a product with triclopyr as the active ingredient works very well (Remedy Ultra, Garlon, and Crossbow are some common examples).  Another very common option would be products containing 2-4,D as the active ingredient (many brand names).  Any of these are selective at killing broadleaf plants without killing grass.  Follow the label directions.

If this is in a pollinator plot for your bees and you do not want to kill plants like clover, you could remove the poison hemlock mechanically.  Poison hemlock is a biennial and does not spread through roots or rhizomes.  If it is kept mowed occasionally, to where it is not able to go to seed, it could be controlled over a few years.  Care should be taken if mowing.  Do not use a weed eater which could more easily result in sap from the poison hemlock entering your mouth or eyes.  Wearing long sleeves, long pants, gloves and eye protection is recommended. 

Poison hemlock is very toxic but the danger is when it is eaten or gets through mucus membranes such as your eyes.  Wild parsnip is a similar looking plant that has the same growth habits and is sometimes found in the same location as poison hemlock.  It is not toxic but It has a compound in the leaves and stems than can result in blisters so it sometimes makes people think the had a reaction to the poison hemlock when it was really the wild parsnip.