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A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Monday - March 28, 2016

From: Waltham, MA
Region: California
Topic: Poisonous Plants
Title: What plant looks like poisonous water hemlock
Answered by: Nan Hampton

QUESTION:

I thought that hemlock was a tree. I grew up in Carmel Valley, CA. As a kid we used to play in fields that looks just like this stuff. Some were over six feet and an inch around. In summer we pulled them up and made arrows of the stalks. They were hollow inside and in the spring we would cut them off and wait for them to fill up with water and drink it. We even ate the white pith in the stems. Obviously, they could not be hemlock. I'd be dead now. What could they have been

ANSWER:

That's the problem with common names, they may refer to several different species of plants—even different types of plants (e.g., woody versus non-woody plants).  There are hemlock trees:

Tsuga canadensis (Eastern hemlock)

Tsuga caroliniana (Carolina hemlock)

Tsuga heterophylla (Western hemlock)

Tsuga mertensiana (Mountain hemlock)

There are also a variety of non-woody plants with "hemlock" in their names:

Cicuta maculata (Spotted water hemlock)  Here is more information from University of Florida Center for Aquatic and Invasive Plants and North Carolina State University Cooperative Extension.   This species occurs in all the lower 48 states (including California) and Alaska (see the USDA Plants Database distribution map).

Cicuta bulbifera (Bulblet-bearing water hemlock)  Here are photos and information from Illinois Wildflowers.  It occurs in the northern part of the United States and Canada (not shown in California) according to the USDA Plants Database distribution map.

Cicuta virosa (Mackenzie's water hemlock) occurs in Canada and Alaska according to the USDA Plants Database distribution map.

All the above species in the Genus Cicuta are extremely poisonous.  See Wildwood Survival.

The non-native Conium maculatum (Poison hemlock) from Europe occurs over most of North America and is extremely poisonous.  Here is more information from Montana State University Extension and from PubMed.

Conioselinum chinense (Chinese hemlockparsley) occurs in the eastern half of the United States according to the USDA Plants Database distribution map. It has hemlock as part of its name but I couldn't find evidence that it is poisonous.

I suspect the plants you played with as a child were Sium suave (Hemlock waterparsnip)  These occur in California and all over North America.  See the distribution map from USDA Plants Database.

Here is a quote from the species page: 
"Water-parsnip is so similar to its highly poisonous relatives (such as spotted water-hemlock), it is better left alone."  You were very lucky that they weren't Conium maculatum or Cicuta maculata (or any of the other species of Cicuta).

Here are more photos and information from Illinois Wildflowers, Survival Plants Memory Course (gives features to use to tell this plant from the poisonous Cicuta species), and from Ontario Wildflowers.

 

From the Image Gallery


Spotted water hemlock
Cicuta maculata

Bulblet-bearing water hemlock
Cicuta bulbifera

Mackenzie's water hemlock
Cicuta virosa

Chinese hemlockparsley
Conioselinum chinense

Hemlock waterparsnip
Sium suave

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