Tall weed or short foal? Field mustard plants that grow here are aggressive and hardy. The locals think of them as invasive weeds, but they are, in fact, a winter annual herb able to survive freezing temperatures and frost. They grow waist high by the spring and often large patches grow so tall they tower over the horses, hiding them completely. The mustard’s tall, woody stalks linger long after the plants lifetime into the summer and fall creating forests of thin branches. The stalks can be heard breaking and crackling as the horses move through them, often giving away the horse’s hidden locations a hillside away. This little foal is a perfectly normal size; the field mustard is just tall.