First let me start off by saying that this is a natural dyeing technique, NOT, I repeat, NOT, a recipe. As delicious as they may look, pokeberries are poisonous (not deadly) if ingested. Wear rubber gloves, and no snacking.
So, with that disclaimer – here is what you do.
Collect your pokeberries. They are normally found here in the Northeast growing among all the other wonderful weeds on the roadside. They are a perrenial. Once you know what they look like, you will start seeing them everywhere.
Find a lovely small pumpkin and carve into it as you would a Jack-o-lantern (no face). Empty the guts and separate out the seeds.
Take your pokeberries and squish them together with your pumpkin guts and your yarn. Try to have as much fun as possible doing this.
Cover your pumpkin and put it somewhere to rest and do it’s magic.
Wait a day or two until your pumpkin starts cooking (fermenting). Take your yarn out of the pumpkin, air dry it, then replace it. Squish it back into the pumpkin/ pokeberry goo. Do this for several days until you can stand it, or the pumpkin no longer. It can get rather smelly.
When you’ve had enough, remove your yarn, rinse it in pure vinegar, then rinse it out in water with a wool wash.
If all goes well you should have a surprisingly bright magenta/ purple color. I am guessing that the varigation in the skein in the picture was caused by exposure to oxygen in the pumpkin, probably not enough pokeberries. Although, I must admit, the surprise factor in natural dyeing is what keeps me coming back for more. This is probably one of the most fascinating natural dye experiences I ever had. Have fun! Oh, btw, most natural dyes are sensitive to light, so to preserve your color, store your yarn out of the sunlight.