I planted some Jerusalem Artichokes earlier this year ( for the first time in my life! ) and have no idea when to harvest them, They are currently about 2 ft. high and thriving ! Thanking you in anticipation,Paul.
Jerusalem artichokes will grow to about 8ft each year! I usually start digging them up late Autumn, but they can be left in the ground or stored over-winter. If you want to get really technical, try this link http://www.pfaf.org/database/plants.php?helian thus+tuberosus
I no longer have the room to grow these unfortunately. I used to start to harvest round about the end of October, and continue to harvest as I wished to use them. Inevitably you will leave the odd few in the ground to start off your crop next year. I understand that it is possible to harvest in one go, providing you have suitable storage facilities.