In general, most Hybrid Perpetuals with heavy Damask Perpetual ancestry (as opposed to those more Bourbon-like, and the later ones with more Tea in them) do need to be "fed well" in order to keep "blooming well", but will "live well" just fine without. From what I've come to learn after growing them, they bloom when "late Spring conditions" -- milder weather, and an influx of water and nutrients -- trigger new growth. A prune after flowering helps as well. In the meantime, they hang in there and survive just fine once established, even if they don't bloom.

:-)