Hi Amy,
I’ve just put in 250 Narcissus Pseudonarcissus Obvallaris and 100 Crocus along the back of a 30′ No-Dig Herbaceous Border.
For the Narcissus I dug short trenches about 18″ long and 8″ deep. I lined these with 1-2″ of grit and pushed the Bulbs into the grit and then back filled. The Crocus where done in similar fashion but not quiet so deep, around 6″ in fact.
I did it this way as I intend these plantings to be permanent and therefore I’m unlikely to be disturbing these areas again (at least not to that depth).
Whilst this is technically “digging” the important point which Charles makes is to not disturb the soil unnecessarily.
Bulbs such as Tulips and Narcissus need to be planted deeply so soil disturbance is unavoidable in this instance.
I have planted Crocus in the past by simply lightly pushing into the soil surface and covering with a 2″ layer of compost on top. But these would not have been intended as permanent plantings. Over the course of 6-8 months that 2″ layer of compost disappears leaving the Corms exposed on the surface making them easy to harvest for replanting. This system works really well around established Trees where the soil can be really difficult if not impossible to dig.
I started doing no-dig with my vegetables and over time went to no-dig with shrubs and flowers and I find it extremely successful.