EEK!! Don’t Touch That It’s…

Oh… nevermind…

This week we examine a much maligned and oft confused native.  I guess we could file this one under “Everyday Flora” as well, though the blooms on these are long gone.

Toxicodendron diversilobum

Toxicodendron diversilobum

The scientific name is a perfect description, “Poison tree, differently lobed leaves”. The bane of hikers campers and clueless bushwhackers, poison oak is nevertheless a ubiquitous and sometimes beautiful denizen of our woods and trails.  The all too familiar “leaves of three” are the telltale hallmark of the urushiol-laden menace.

To make things more complicated we have quite a few lookalikes in our neighborhood and without flowers or fruits sometimes it is very hard to tell the difference.  Rambler to the rescue.

Note the 3rd leaf stem is elongated

Note the 3rd leaf stem is elongated

This of course is poison oak.  It can take many forms from a low shrub to a creepy crawly vine to a ten foot tall behemoth.  Leaves can be anywhere between shiny and matte.  The key feature is that third leaf.  It has a lengthy pedicel (stem).  Always.

The first plant that I learned (thanks Cope!) that could be easily confused with poison oak was blackberry:

Rubus ursinus

Rubus ursinus

They grow in similar areas.  Blackberry certainly has a much more viny growth habit, and is rarely if ever woody.  Poison oak is definitely woody.  The easiest way to tell blackberry is the fine tiny thorns going up and down the stems.  Poison oak NEVER has thorns or spines.

The second easily-confused plant comes with a story an acquaintance related recently.  She and 2 male friends had gone backpacking in the Sespe.  Darkness was approaching and they hadn’t found a camp yet.  They finally stumbled to a site and saw it absolutely rife with this:

Rhus trilobata

Rhus trilobata

Oh no the boys lamented… But the bright young lady (former acolyte of mine) knew right away, have no fear.  This is only the innocuous cousin of poison oak, known as squaw bush, or basket brush for you PC folks out there.  A key feature is that 3rd leaf we talked about earlier.  On Rhus trilobata there is really no pedicel (stem), the leaf attaches to the main stem directly.

Clematis liguisticifolia

Clematis liguisticifolia

Clematis is sometimes confused with poison oak.  Like blackberry, clematis is viny and never woody.  More importantly it generally has more than the 3 leaves, usually 5 and sometimes 7.

Rupertia physoides

Rupertia physoides

Last and least we’ve got California tea.  I have to admit I was fooled the first time I saw it in Wills Canyon

The leaves have a highly polished luster and are all generally the same exact shape.  It is a very low creeping shrub and never woody.

As long as we’re on the subject poison oak has two close cousins.

Rhus ovata- Sugar bush

Rhus ovata- Sugar bush

Rhus intergrifolia - Lemonade berry

Rhus intergrifolia – Lemonade berry

Sugar bush is rare around here except on the Ventura River Preserve, and lemonadeberry is more common towards the coast.  Some people have been known to have allergic reactions handling them.

You are now officially apprised of the beautiful but potentially irritating poison oak and all of its impostors, dopplegangers and wannabes.  Go forth into the wild with confidence my friends.

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2 Responses to EEK!! Don’t Touch That It’s…

  1. Anthony Copioli says:

    Rambler, I wish I was close enough to come ramble with you sometime, hopefully soon! With your permission, may I throw out some botanical cannonical? The stem holding the leaflets of a compund leaf is a petiolule (the stem of a simple leaf would be a petiole), and of course the pedicel is the stem of a single flower (peduncle is a stem that holds an inflorescence). So, that center leaflet has an elongated petiolule as TODI has a compound leaf. The Rubus, has “prickles” which are technically outgrowths of the epidermis, thorns are modified stems and arise out of nodes. Everyone including me still says thorns anyway…Now, this is off my apical meristem, or top of my head if you will. Ill double check my Botany textbook when I get home.
    Enjoy the rambles rambler!

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