If you deadhead, then give your plant a few handfuls of compost around the base or fertilize, many will rebloom in several weeks.

Or, you can leave the stems in place and allow seed to set which you can gather and sow...My species delphs self sow regularly, the hybrid types only very occasionally in my zone.

I would cut the stems back when the new growth is about 4-6" tall. Fertilize with manure and mulch with compost.

Delphs aren't the hardiest perennials in the garden to begin with, and letting the plant go to seed weakens it and may shorten its life.

PMC's got an advantage with her zone- the silly, beautiful things are better suited to canada than Pennsy, and she's got a zone on us, there...

deadheading makes stronger plants. leaving the stalk to go to seed (when the third from the bottom pod cracks, you can shake the seeds out, and cut down the stalk) makes more plants.

and drifts of them are on par with drifts of lupines, which are rapidly becoming my favorite flower in the world :)

You guys must be right about the zone thing. This year the kids got me a big one, already in bloom for Mother's Day. It came with one flower stalk in bloom, and since planting has developed 2 more stalks which are in bloom now.

I am trying to develop a perennial garden and evidently I planted a delph last year that I thought had died. Guess who showed up this year? Yep, it is not huge and it did put out one flower stalk.

So who knows how many I will end up with next year???

hmmm...I don't 'know if they spread by clumping or not...but if you leave the bed undisturbed, and let them go to seed... you could wind up with 20 younglings next year, which would mean that the year after you would have maybe 15 ready to flower. (I'm pretty sure they start flowering their second year- like I said, it's a struggle to grow them here)

Yes....they spread by clumping....some cultivars better than others.
I have had the best luck with Magic Fountains.....and I don't let them re seed....I want to know what I have.
Linda C