Hello & welcome, Steve. I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
How long ago did he eat the plant? What was it?
Has he had any retching, gagging, lip licking, or vomiting?
Can he keep water down despite the hacking?
Are his gums pink or pale/white? Moist or sticky?
Can you take a breathing rate for me (just count his breaths for 10 seconds + multiply that by 6)?
If you press on his belly, does he have any discomfort, tenderness, or tensing?
Any chance he ate anything else (ie non-edible items, medications, etc)?