It is virtually impossible to have any plant bloom according to a calender. They don't pay any attention to dates :-)) It is soil and air temperatures and day length that triggers flowering as well as the plant genetics. You can try planting out later but there are no guarantees that tulips will be blooming in May. Even in my climate, they are done by the end of April, often quite a bit earlier.

Darn, if only they could be penciled in to my schedule ;). Thank you for the quick response! I think I will try and stagger my planting a bit, at least with a few bulbs to see what happens. I am sure I can catch at least one of the early spring holidays between Valentine's Day, Easter and Mother's day!

You can plant the later blooming lily-flowered types, along with single lates and viridiflora group.. Queen of Night, for example, is a May bloomer.

I don't understand zones and places in US. But you want the tulips to flower late, and this will be difficult.

If we want them to flower early, they can be chilled in the fridge (but never put them near fruit. The beer fridge is the one to use, if you have a beer drinker).

To encourage later flowering, you will at least need the latest flowering varieties you can find (which is obvious but I am getting to the point eventually). A bulb grower will be able to tell you some late ones and hopefully some of them are ones that you like.

But how to get your late flowering tulips to flower later than they would want to? I've tried this and it's not easy.

I don't think planting later is a good idea but it doesn't hurt to experiment if you have the numbers. I think I would try to keep them cool (this is not the same as chilling a bulb in the fridge before planting, which gives them their chilling period earlier). I'd keep them cool by having their pots (if they are in pots) in a slightly shady spot.

If you are growing them in the ground, maybe choose a few different sites.

We have 'Floriade' here in Australia, which goes from mid September to mid October and there are still some tulips deciding to flower at the end of it. Even so, you want them a little later - the equivalent of our November I think.

Anyway, I hope you manage it and I'd love to hear how you went.