Hemlock is only slightly toxic. But also looks like spotted hemlock which is fatal. Also alike is cow parsley and carrots. They are all Umbelliferae (carrot family of Apiaceae): the inflorescence looks like a large, umbrella -like screen. This consists of small screens of (mostly) white stemmed flowers. They have a pentadentate calyx, five-leaved crown, five stamens, a pistil with a below standing ovary and two styles.

To recognize them you watch the carpels at the foot of the small screens and / or involucres sheets at the foot of the big screen.
Are the crown (flower) petals equally long and similar in shape, are they heart-shaped or round or rather curling?
Are the seed pods oblong or more spherical, smooth or with ribs and bumps / prickles?
Is the leaf wide or narrow, rough or smooth, deep or low cut, assembled or not, single-, double - or triple- finned?

echtekamilleA composite sheet has on the petiole several separate sheets.
In a single finned (pinnately branched) leave the constituent leaves are opposite to each other on short stalks.
Double finned (pinnate) means that on a separate petiole there are opposing leaves on short stalks.
Triple finned (pinnate) has one more split again with leaves.
Feather gap: the sheet has cuts from a quarter to half of the vein.
Feather shape: cuts from half the vein almost to the midrib.

The hemlock (Chaerophyllum temulum) is a biennial plant and got its (Dutch: crazy) name because cows that eat a lot of them behave as if they are drunk. Hemlock is also (slightly) toxic. In the literature, no poisoning cases are described on humans.
The stem is erect, purple-red with a transition zone with red spots and dots. He has fairly long erect hairs that partly stand out.
By this hemlock is easily recognizable. The more robust, spotted hemlock (Conium maculatum) also has that stains, but misses the hair.
The leaves are dark green and later sometimes purplish. They are two - to three-fold feathered and the leaflets are ovate to oblong, blunt and toothed.
The white flowers are about 2 mm in size and form composite screens with five to twelve rays. If the flowers are still in bud they hang. The petals are not hairy.
The screens with still unopened flowers hang down somewhat kinked.

Socrates deceased by drinking the Greek poison cup. The poison herein may have been made with the seeds of spotted hemlock, an almost lookalike. So here we have a Deadly Award.

All parts of the spotted hemlock (Conium maculatum) are toxic. The stem is bald and red-brown spotted at the base. When rubbed the plant gives a murine musty smell.
The flowers form a composite screen with a diameter of 2-5 cm. They are white and have a diameter of about 2 mm. There are five petals with a curly top.
There are ten to twenty rays and involucres with three to five leaves all turned to one side. The plant blooms from June until autumn.
The leaves are two - or three-fold feathered, and can be 30 cm long.
The spotted hemlock has an ovoid to round fruit with five ribs, but without oil stripes.
The plant contains the neurotoxin coniine of which more than 100 mg (about 6 to 8 fresh leaves, or a smaller dose seeds or root) for an adult is lethal. It creates an ascending motor paralysis with possible paralysis of the respiratory muscles. Death is caused by a lack of oxygen to the heart and the brains. Death could be prevented by artificial respiration until the effect subsides about 48-72 hours later.

Cowbane is less, but also very toxic.

Cow Parsley (the hollow stem is used to make whistles) has a spicy aroma. Of course, not to be confused with spotted hemlock!
Cow Parsley has no involucres at the point around the big screen, or at most one with 1 to 3 small leaves and eye lashed, not shared carpels in small screens (five leafs).
The composite screen has 1 - to 3 - rayed basic screens that each contribute more than 6 smaller screens. The fruits have a short beak.
The leaf is triple finned.
The leaf sheath is densely hairy on the ribs and woolly fringed at the edges.
The stem has, only at the lower half in the short ribs, back directed hairs.

Chervil (Anthriscus cerefolium) is an annual with a smooth, hollow stem that is only hairy above the buttons. The screen rays are also hairy.
The flower is white with a diameter of 3-4 mm. Each flower has five petals and involucres. The composite screens have eight to fifteen screen rays. Chervil has cylindrical, hairless fruits with a beak that is half as long as the fruit. Only the wild form has short barbs on the fruit. The fruit is a two-piece split -fruit with one seed achenes.

Carrot, whose root is edible, belongs to the same family and therefore looks a bit alike.

The stem of Angelica is hollow, round, striped, branched and frosted. He has hemispherical screens and an inflated leaf sheath. There is no involucre, but many carpels.
There are two types: ordinary angelica (Angelica sylvestris) and large angelica (Angelica archangelica).

Take a class naturalist, and walk a year or 2 in all seasons - along with experienced experts to identify plants correctly.