I'd like to know how to grow delphiniums, period! Between slugs and mildew, I have no luck at all! But I was intrigued to hear of red ones..... that's new to me. I hope they do well for you, but I can offer no help at all. Sorry!

Can these delphiniums stand watering in summer? Do they need protection in winter?

From the Ontario Rock Gardening site they say nudicaule can be germinated if you sow @ 20C (about 70 F). Seed germinates within 3 months. Another resource I have says that Delphs should get a 1/16th inch covering and sown in a light peat mixture.

If you do a google search you will probably find Zone info for these. Most likely they will be fine, but I would protect the first year seedlings.

Where did you get the seeds?

Good luck,
jb

Here is a link that might be useful: Ontario Rock Gardening

Where to get the seeds: I found them in a seed catalog. You can also get them from plant society seedlists. Chiltern is selling both.

Nudicaule is interesting, but not real showy. Cardinale can get very tall and spectacular.

I may dig the tubers up and store in dry peat for the winter.

That new red hybrid derivative made the rounds a few years ago, even supermarkets had them flowering in 2 gallon pots. I think mine petered by last year, so I only got a few years out of it at best. It was in a combo pot in soilless potting mix, with other plants, so heavy soil was not the problem. We have not been having cold winters, so if it froze it was tender. Haven't seen any slug action there, but that is always possible as they do get around during damp weather.