Today I was asked for my recipe for thistle rennet.  I use Canadian thistles (Cirsium arvense (L.) Scop) for my rennet. I pick them as they are drying naturally, this is before you see the white fuzz.  I then put them in quart jars and pump and seal the jars.

Making rennet.
I will take three thistle heads and put them in my food processor.  I process them till they are on the verge of turning to powder.  To this I add 3/4 cup of distilled water and process them once again. At this time I add 3/4 cup of distilled water once again. I let this sit in the processor for an hour.  I then process them a few second.  I pour this into a small colander with fine material, cheese cloth or my special cheese making cloth, lining the colander. The fluid I get from this is the rennet. It will be very dark if you have done this right. I leave the thistle mixture in the colander for about twenty minutes to drain.. I have kept this in the frig for a week and it has remained good. I use to just infuse the heads in a quart jar of water and found out it took so much of this rennet to curd milk.

I find it takes a little more of this rennet to curdle the cows milk than the goats milk.  I have been using two teaspoons of this rennet to two gallons of milk on an average.