Wild Onion Allium vineale Depending on who's description you read, this is sometimes called wild onion and sometimes wild garlic. It is much more a garlic than an onion. The plant grows in grassy-looking clumps. The leaves are wiry, round and hollow. It seeds prolifically. I have pickled it with vinegar and cinnamon sticks.
Devil's Trumpet Datura wrightii Datura commonly changes its appearance depending on its location, so distinguishing Datura wrightii from Datura intoxia can be tricky, but I've concluded to the best of my research that this is Datura wrightii.
Black Walnut Juglans nigra In my area, I only know of one black walnut that has the very small nuts. The rest of the black walnut trees (very widespread here) are the very large nuts (slightly larger than a golf ball) which I think are actually Eastern black walnut.
Western Soapberry Sapindus saponaria var. drummondii At last count, the soapberry borer (from Mexico) has reached 33 counties in Texas. You can find info and images and what to look for at http://tfsweb.tamu.edu/main/popup.aspx?id=5316
and you can report it to the Texas Forest Service at http://texasinvasives.org/action/report_detail.php?alert_id=4