Blightrose:

A black rose that is poisonous. When ingested, it closes off your lungs, making you suffocate to death, and it also turns your veins and lips black. Mechanically, you must cause a DC 14 Constitution saving throw or begin suffocating. You repeat this saving throw every minute. 
The Blightrose tends to grow in places riddled with death, undead, and negative energy, as the flower seems to feed off of it.