The toxic principle of buttercups is called "ranunculin" as the weed is part of the Ranunculus genus. When eaten fresh, the toxin has an irritating effect on mucus membranes. Blisters are often seen along with oral ulcerations and possibly drooling. The acrid taste usually makes them unpalatable, however animals residing in overgrazed fields may eat them out of desperation. Continued ingestion may cause further GI damage and lead to colic or diarrhea, however animals quickly learn to leave buttercups alone and it rarely progresses beyond oral irritation. Once dried, the toxin becomes neutralized, so don't worry if you see it in your hay.
Clover is easily identified. It grows low to the ground and has 3 leaflets with a distinctive white "V" pattern on the top of the leaves. Late summer is when it flowers, and the the colors can be pink, red or even purplish. The fungus can be seen as black spots which usually appear on the bottom of the leaves first. It will spread and cause the entire plant to eventually die off.
This perennial contains hypericin, which is a pigment that reacts with light. After ingestion, signs of primary photosensitization occurs with 24 hours. What does that mean? Once eaten, the hypericin distributes throughout the body. One type of cell it enters are skin cells. When UV light interacts with these skin cells, the hypericin becomes activated and interacts with cellular components thereby causing damage. Once damaged, we begin to see clinical signs such as sunburn, dermatitis, pruritus or ulcerations develop. This often effects lighter colored areas of skin more than darker pigmented areas due to the amount of light contacting the cells. Oral irritation may occur as well. Once again, removal of the source and treatment of the dermatitis is sufficient.
The leaves have serrated edges, and fan out in a palmate shape. These plants can grow anywhere from 20" to up to several feet in height. If your horse should ingest this weed, then clinical signs may include depression, drowsiness, ataxia (unsteadiness) and possibly hyperresponsiveness or tremors. You may also notice an increase in feed consumption. Okay, the last one is a little tongue in cheek. But seriously, if a 1000 lb animal is drowsy and having difficulty standing, they pose a risk to themselves as well as any people that may be around them. If a horse does ingest marijuana, then signs should resolve within 24 hours after being removed from the source.
So there you have it! After 3 posts about plants, there's not a whole lot more to say. Yes, there are some that we did not mention, but we tried to focus on ones that are either really common in our area or just plain interesting. We hope you found this enjoyable and educational!