Rachel, I would pot the plants up into one gallon sized pots planting them several inches deeper than they are in their original containers, pinch the tops out of any vines already growing, and then put them outside on sunny days, and bring them in if the weather guessers call for extreme frost. You can always pinch back any top growth as it begins to grow to prevent it from becoming a tangled mess and unruly.

I have several clematis in pots that stay outside all season long and am located in Kernersville, NC where we still are having cold nights. Clematis will do just fine growing outside in the colder temperatures provided that their root balls don't freeze solid for longer intervals. The top growth might get zapped back but if the roots are well established as they seem to be from your description, then they should be okay.

Thanks, I've potted them up deeply and am going to prune them back. How far down should I prune them? Just the terminal tip, or down to the soil line? We shouldn't have a frost that lasts long enough for their root balls to stay frozen, especially since they are in black pots with some sun shining on them. At what point would it be safe to plant them in the ground, or should I let them grow in pots for their first year? They were shipped in 2 1/2 inch pots.

Thanks!!

Rachel

Rachel, I rarely trim new plants all the way back back to the soil line, especially newly planted ones. I normaly trim 3 or 4 inches above the ground or so that there is at least one bud above the soil. Planting them deeper is good since it buries dormant nodes that can produce new vines from the soil.

Not having seen how well established the root systems were on the plants you received, it is hard for me to say whether to plant them now or wait until fall. If this summer is anything like last year's, then in a pot, you can see if the plants need water and you can keep them well watered and fertilized. I always prefer planting most things in the fall since in our zones, the air temps. have started cooling down, rain is usually more plentiful and even if it isn't it is easier to keep the soil moist, and the plants will have all fall and well into winter to get themselves established so that next year they can take off.

One other thing, Princess Diana can be prone to mildew in our area--at least it is in my garden. At the first sign of mildew, start spraying with a mildewicide or it overtake the plant. Some people don't have issues with mildew on it so maybe you will be lucky. In the future, if you like Princess Dianna and want another one similar to it but without the mildew issues, try the Duchess of Albany. It is a much more vigorous grower in my garden than is Princess Dianna.

Here is a link that might be useful: Duchess of Albany