Getting ready to work dahlia bed up but first wanted to find out if anyone had a good idea on how I can incease the number or size of my tubers....I work in a lot of cow manure..have good size plants but the last couple of years I don't think the number or size of the tubers has been very good........I know each type will generally produce different type, size, color and number of tubers but over all I think the count is down....sometimes a huge plant and no tuber except the mother tuber......