Dig the Yellowroot in the fall from mid Sept. on to about mid Oct.
Yellowroot usually grows in the same areas as Ginseng, I dug alot in the 80s to mid 90s, and always had good luck in older clearcuts . I quit digging around 97 when the price of Yellowroot dropped 50% to around 14 to 16$ per pound.
Hickoryjacks seem to sprout in our area after a few days of steady rain.
April and May and in the fall Sept.,Oct. is good if you get the rain.
We harvest them on dead Quaking Ash, Elms, Hickory, Maples, Poplars and have picked alot off of Poplar stumps.
I would suggest to you to have someone who is familiar with Hickoryjacks to help you to identify them before actually harvesting them.