I have tubers I grew from seed of C. hederifolium and I'm wondering about the appropriate depth to plant them outside in where I hope they will naturalize and thrive. I have had tubers of C. hederifolium and C. Coum that froze to mush during the past winter's cold snaps in my USDA 6a climate. These sadly departed geophytes were planted with the top of the tuber barely covered, and were located in a bed of Meehania cordata, with evergreen branches strewn atop the bed to improve their chances of surviving winter cold. The tubers range in size from about 7-15 mm in diameter. I fear that if I plant them too deeply, there will be problems with emergence of foliage (and flowers) that will result in the demise of the tuber. Can anyone provide practical recommendations that will help me as I'm crouching in my border? Jonathan Knisely New Haven, CT