<p>Euphorbia lathyris
</p><p>Euphorbia is not only *thought* to deteur digging rodents (which is all of them if you get down to it).  All member of this genus exude a milky, bitter sap -- not unlike a dandilons.
</p><p>According to the chemist @ Newport Cactus Gardens, most new world "cacti" are not that at all:  &lt;a href="<a rel="nofollow" class="external free" href="http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbiaceae.html">http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbiaceae.html</a>" rel="nofollow"&gt;Euphorbiaceae &lt;/a&gt; instead of Cactacae.
</p>
Cacti have spiny nipples all over them.  I swear they're called &lt;a href="<a rel="nofollow" class="external free" href="http://www.bcss.org.uk/areole.pdf">http://www.bcss.org.uk/areole.pdf</a>" rel="nofollow"&gt;areoles&lt;/a&gt;.<br>Gopher spurge
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/26084283@N00">Marie Richie</a> from Portland, Cascadia
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