I have always been very interested in natural entheogens, especially obscure ones and have had many experiences with them, from skullcap to petunias. I recently I was able to read up on periwinkle and was very excited because I have a bunch growing in my front yard. I promptly picked several leaves, maybe a dozen, and let them semi-dry before smoking.
They take a very long time to dry, and being very impatient, I picked out the driest leaves I had to smoke. When everything was said and done, I smoked two bowls. The smoke was very harsh but not too resinous so there was little coughing.
After a few minutes, I began to notice mental effects: my mind became clouded like a faint buzz from smoking some indica strain cannabis, but at the same time my mind felt as if it was clearer like it was cleaned. I felt a mild, but considerable sense of contentment and oneness with nature. Colors were barely brightened and I kept having peripheral hallucinations that honestly freaked me out. I kept thinking that an animal was scurrying around or trying to sneak up on me. Sounds were enhanced, not necessarily in a trippy way like with cannabis, but sounds were louder and more pronounced and made me paranoid a couple times. Getting up and walking around was pleasing, my yard seemed vaster and seemed to breath harmoniously with me. Staring at the stars and full moon filled me with awe. It was settled, this is definitely not a placebo!
The effects lasted for over a half hour and coming down felt somewhat similar to coming down from cannabis. Talking to my sober brother was a bit confusing, I was filled with a cannabis type paranoia.
Overall the effects were mild but that does not mean they were disappointing. The fact that it was subtle was actually refreshing in a way.