During spring, before you plant the overwintered root mass, is when to divide dahlia tubers. If you divide when you pull the roots for overwintering, you may find they are not viable in spring, so wait a bit before splitting dahlia tubers. This is because each tuber must have an eye or growth bud that is viable.Click to see full answer. Also to know is, can you cut dahlia tubers in half?Dahlias are generally propagated by dividing the root tubers. You can do this in the fall before you store them away for the winter or in the spring when you are ready to replant. Many gardeners prefer to divide dahlias in the spring because the eyes are more visible and the plants have survived the winter.Similarly, will shriveled dahlia tubers grow? Check tubers periodically through winter for rotting and drying out. If the tubers appear shriveled, mist them lightly with water. If any start to rot, trim the rotted portion of the clump so it won’t spread. The tubers are fragile, so be careful when handling them. Regarding this, do dahlias multiply? The usual way to multiply a dahlia is to divide the tuberous roots after winter storage. If the supplier will ship tubers at least two months before your planting date, you can do it. It’s a great way to get five or six plants from a single tuber-immediately, before the season even starts.Can I leave dahlias in the ground over winter? Overwintering dahlias in single beds If, like me, you grow dahlias for cutting in big beds, you can leave them in the ground over winter. Mulch your dahlias in late autumn under several inches of mushroom compost or similar and just clear this away once the worst of the frosts are over in the spring.