Common water hemlock (Cicuta maculata)

Description:

This perennial native plant is 3-6′ tall, branching occasionally. The stout stems are smooth and hairless; they can be green or purple, sometimes with purplish lines or spots. The lower portion of the central stem is hollow. The compound leaves are odd-pinnate or double odd-pinnate; they alternate along the stems. The lower compound leaves are up to 1½’ long and ¾’ across; the upper compound leaves are much smaller. Each division of a compound leaf often has only 3 leaflets, but sometimes there are many more. The petiole of each compound leaf forms a sheath around the stem. The hairless leaflets are up to 4″ long and 1¼” across. They are narrowly ovate with a wedge-shaped bottom, and are strongly serrated, often folding upward along the length of the central vein. The radial veins spread to the notches, rather than the tips, of the teeth along the leaf margin.

The upper stems occasionally produce compound umbels of small white flowers. These compound umbels are up to 6″ across and consist of 10-20 umbellets. An umbellet has about 12-15 flowers. Each flower is about 1/8″ across, consisting of 5 white petals, 5 white stamens, and a divided style. The little petals are constricted at the base, and have notched tips. The blooming period is mid-summer, and lasts about a month. The flowers have a slight fragrance that is sometimes detectable. Each flower is replaced by a small 3-angled fruit. The root system consists of several fleshy roots at the base of the plant; they are ovoid or oblong in shape. These fleshy roots are exceptionally poisonous; the stems and foliage are somewhat less poisonous. This plant spreads by reseeding itself into adjacent areas.

Cultivation:

The preference is full or partial sun, and wet to moist conditions. Some standing water is tolerated, if it is temporary. The soil should contain lots of organic material so that it can retain moisture. Foliar disease isn’t a significant problem for healthy plants in an appropriate location.

Distribution Map:

Range & Habitat:

Water Hemlock has been observed in nearly all counties of Illinois (see Distribution Map). It is occasional to locally common. Habitats include moist open woodlands; wet depressions in moist black soil prairies; marshes, swamps, and seeps; and roadside ditches. Water Hemlock prefers moister locations than the introduced Conium

maculatum (Poison Hemlock), and so these two species rarely compete with each other for the same ecological niche. It is not uncommon to find Water Hemlock growing where Iris virginica shrevei (Blue Flag Iris) occurs.

Faunal Associations:

The exposed nectar of the flowers attracts primarily insects with short mouthparts, such as flies and wasps. Other flower-visitors include short-tongued bees, small butterflies, and beetles. Highly unusual wasps visit the flowers, including Cuckoo wasps, Chalcids, Braconid wasps, Spider wasps, Paper wasps, Mud Daubers, Eucoilid wasps, Perilampid wasps, Sapygid wasps, Astatinine wasps, Wild Carrot wasps, and Velvet Ants (the latter are actually wasps, notwithstanding the common name). The caterpillars of Papilio polyxenes asterias (Black Swallowtail) feed on the foliage. The toxic foliage and roots are usually left undisturbed by mammalian herbivores, although cattle and other livestock sometimes eat this plant with dire results. The fleshy roots are especially toxic: just a small piece can be fatal.

Comments:

Water Hemlock is reasonably attractive and eloquent, while the flowers provide nectar to many beneficial insects. It is fairly easy to distinguish Water Hemlock from other members of the Carrot family because of its double compound leaves and rather large leaflets that are rarely lobed; many other members of the Carrot family have simple compound leaves, or the leaflets are much smaller and more lobed. On Water Hemlock, the radial veins of the leaflets spread to the notches between the teeth, rather than at their tips, along the leaf margin. Apparently, no other member of the Carrot family in Illinois has this characteristic.

Sourced From: http://www.illinoiswildflowers.info/wetland/plants/water_hemlock.htm