Plant-based rennets for cheese

The Medieval Cheese Blog is an amazing resource. I'm planning on trying a couple of these suggestions for making cheese- Plant-based cheese rennets

The most accessible plants mentioned are nettle, thistle, cardoon, sorrel and lady's bedstraw (that's a very multi-purpose plant!). The other option she mentions is the sap of a fig tree. While it's possible to grow those in Ontario, unless you live in zone 7 it's a serious pain to try and keep them.

I've harvested a few early sorrel leaves from the garden, so I'll see how it turns out.