I'm making Motherwort tincture this week (harvested on June 20). I'm making Yarrow tincture today or thereabouts. I'm cutting all the flowering comfrey for both infusions and infused oils. I'd love to make St. JOhn's Wort oil but have no medicinal SJW! Bah.
Harvest while in bloom, like the picture. A bit pokey. Look for the pointed leaves. Likes partial sun and will be in the green areas; in the alley, by the pathways.
*Note: made tincture this weekend. I couldn't get much motherwort, just enough for a pint jar. This will make 8 oz of heavy tincture though. If it generates any interest from others, I will make more!
Comfrey: You can spot comfrey by its big hairy, dark green leaves. They are wide and nearly prickly. They produce a big flower stalk (much like Borage, from the same family) with purple flowers, and comfrey doesn't take no for an answer! My dad had lots planted or migrate to areas of the yard that he frequently mowed over. And they just pop right back up again, invigorated.
I harvest only the leaves and flowers, no roots. Years ago, scientists "proved" in a lab that the root had so much Allantoin in it that it was dangerous. That's mostly been disproven now. the herb is very healing to skin and I make infused oil from it, so it stays topic/ external anyway. But many other herbalists use it in infusions internally. I'm not there yet. (I use only the garden variety of comfrey with purple flowers. Yellow flowered is a different kind. Look online for more information.)
Also, I am adding to the mix with infused rosemary oil and calendula oil, when mine choose to bloom.