Some plants thrive even in dry years, while others need wet years to really blossom. It's no surprise, then, that this year the University of California Cooperative Extension (UCCE) Fresno office has received several inquiries about potentially toxic plants and how to deal with them. Even if these species have always been present in the seed bank or on neighboring land, this year was a good year for toxic plants to grow large where previously they grew very small – or didn't grow at all.

Common plants that can cause livestock poisoning include annuals such as cockleburs, hairy fleabane, and yellow starthistle, and perennials like curly dock, larkspurs, and milkweeds. Annuals especially tend to respond vigorously to...