Meet Toxicodendron radicans
According to Delena Tull, the author of Edible and Useful Plants of Texas and the Southwest: A Practical Guide, poison ivy takes a different appearance in different parts of the country. So folks from other places may not recognize it. Tull says that there are several types of poison ivy that grow in the Great State of Texas. The type that grows at Dog Park is the classic version—shiny, three-leafed clusters that grow close to the ground but may also vine their way up trees. Our poison ivy doesn't grow near the walking paths but in the shady clumps of trees down by the creek and along the middle pathway. Most people I've talked with get it from their animals after the dogs have chased something into the trees.
Chemistry lesson, anyone? Poison ivy sap contains a chemical called urushiol. The sap can be released by the slightest touch of any part of the ivy--stem, leaf, flower, root, or berry. Your physical reaction depends on how sensitive you are to the urushiol and how intense your encounter is with the ivy or its sap. My father always claimed to be immune to poison ivy, and I must have inherited his tough hide. On the rare occasions that I have gotten p.i., I sported one or two teeny-tiny blisters that were so maddeningly itchy and hot, I can only imagine the agony of being more sensitive.
What about the dogs? After an informal survey of Web sites, I have learned that, in general, dogs are protected from the sap by their oily fur. (Outbreaks of blisters on the exposed tummy skin might be caused by poison ivy, but you should not make any assumptions and check with your vet. When my Muzzy was a puppy, I thought she had poison ivy, but the rash was actually a bacterial infection that was easily treated by antibiotics.) However, the poison ivy sap is easily transferred to us when we pet them. One site recommended wearing gloves and wiping the dogs down with dry towels immediately after they have been in or near the ivy.
For more info about poison ivy (but not dogs), check out this helpful Jane Brody column from the New York Times:
I dare you; try to read it without feeling itchy.
Judging by how lush the ivy is right now, I think we are in for a bumper crop this year. So let's be careful out there.