macman:

My pears of all kinds seem to be less bothered by marginal chilling than the apples. The pears have more concentrated bloom, less blind wood, and better foliage. I've got Bosc, Comice, Seckel, Housi, and Olympic.

Our chilling might be enough different to make a difference. And maybe yours just need more time. But most of my pears bloomed at least a month ago and were frozen out about March 25th.

I had one pear tree that leafed out late this year. It was shaded some by a large tree nearby and once I cut the tree down it leafed out and is blooming now. Though I have an apple tree in full sun that still hasn't leafed out though it was only planted this year so it might still be establishing roots. The tree is still alive and should leaf out in the next week or so. I would just give them more time.

Unfortunately, I suspect that your suspicions may be correct, that apples may be more adaptable to lower-chill areas than pears are.

I'm in Southern California and my Passe Crassane does not appear to be doing so well either. Although it did put out blossoms in late February, it has shown classic signs of inadequate chill, the size of the leaves are very small and the leaf growth has been pretty sparse. (probably only 100-150 chill hours here though)

It's particularly interesting because Passe Crassane was supposedly the result of a hybrid between quince and pear (by French nurseryman Louis Boisbunel in 1855), and quince does grow well here.

Hats off to you for planting this once iconic, but now apparently obscure variety. Despite being a hard Winter pear, it is said to have the most exquisite flavor of any pear variety, on par with or even exceeding Comice.

Unfortunately it is extremely vulnerable to fire blight in other regions of the country, which has probably curtailed its popularity.