So far as I know, and in my experience, delphiniums flower in their first year, and start to deteriorate within 2-3 years, so unless its just they're bigger plants, I can't see what the advantage of 2nd year plants would be. Are you paying more for them because they're 'second year'?

Thats what I thought Bamboo so I will give that a miss they are £1.99 per plant.

That's what I pay when I buy small potted perennials this time of year at the garden centre, so depends what they mean by 'plugs' really.

Hello ... with delphiniums, and some other plug plants, I take this to mean the plant has been tried after its first year of planting and is confirmed it will flower in the first year of customer planting. It is a quick fix assurance for planting straight out. You get a bigger more established plant for your money, with guaranteed flowers, in the same season. If you opt for a smaller first year plug, success rates depend on the receiver, whereas second year plugs are stronger, so the sender has fewer returns and complaints.

Good list of points bilbobaggins - missed the biennial possibility. At £1.99 for a plant ... I would be happy to replant these every few years, if they need it! Though, as you say, you can't beat seeing what you are buying at your local GC, and divide then feed up when they start to slack.

Which variety, Bilbobaggins, one of us might be able to help?!