Hi Steve, from my experience the vast majority of herbaceous peonies grow as fast as the Itohs but there are a few that grow much slower. From what I've seen, if you have a herbaceous root that has a woody part and 1 or 2 yam looking feeder roots it will at least double in size, weight and number of feeder roots in a year, sometimes a bit more than that. I'd say a 1-2 eye division that is fast growing would need to go in a 2 gallon pot to make sure it won't run out of space. A 3-5 eye division with a couple of feeder roots would need to go in a 3-5 gallon one.

What variety is your herbaceous? Do you know if it's a fast or slow grower?

I have no idea because I have a huge variety of them so I might have fast and slow growers. If they double up in size, that shouldn't be a problem just yet.

I planted them ensuring that their is at least 4-5X more soil mass than the tuber mass. Anyways thanks for the info.

For me the minimum pot size for a new division is 3 gallon. Al