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How to Make Thistle Rennet for Cheesemaking



Did you know that you can make a perfectly good rennet substitute from a weed that might be growing in your yard? 

When looking for rennet substitutes, sometimes you need look no further than your own backyard. You may have the main ingredient for homemade “vegetable” rennet growing right at home already. 

This recipe uses Bull Thistle – a purple thistle that is considered a weed in most places. Please make sure the thistle you are planning to use to make this recipe is an actual bull thistle plant and not an imposter. Here is an official description, including pictures, of the Bull Thistle plant, or cirsium vulgare.


Instructions for Making Thistle Rennet


  1. Remove the thistle flower head after it has browned a little on the plant. Pick the head before it starts producing thistle down. Take the flowers in and dry them well in a dehydrator, or merely in a sunny, ventilated place in your house. Once they are fully dried, pick off the stamens or the purplish threads from each head. Put the harvested stamens in a clean, completely dry jar with an airtight lid.

  2. When ready to begin making rennet, take the stamens out of the jar and grind them, using a non-porous mortar and pestle. Grind enough to make 5 tablespoons of powder, to make this rennet recipe. 

  3. Place the measured, dried and ground stamens into a small bowl. Add warm water (not hot, to avoid killing the coagulating enzymes) to the bowl and let steep for about 10 minutes. The water will be a brown, murky color when finished steeping. 

  4. Strain off the liquid. This liquid is the thistle rennet for use in cheesemaking. Use this liquid in place of animal rennet in the amount of one cup of thistle rennet per gallon of warmed milk.


How to Use Thistle Rennet

Thistle rennet should only be used for sheep or goat milk – it will make cow’s milk cheese bitter, especially if aged. Any cheese made with any vegetable rennet will be slightly bitter if aged for a long period of time, (say, over 2 months). Solve this problem by making cheeses with shorter aging periods when using vegetable rennet, or merely eat the cheeses younger. 

If not using right away, keep the thistle rennet stored in a tightly covered jar in the refrigerator. For best results, use it as soon as possible, once the stamens have steeped. Only open up and steep the stamens if using the rennet right away. If not, thistle stamens store better dried in a airtight jar in the refrigerator 



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Bull Thistle


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