You can use them from about 2" upwards, but you need to 'tube' them to do it.
A hollow bone of the right diameter, a bit over a cm in the centre, and you pack the needle bunches in end on (best if you keep them all facing the one direction) and you stitch them tightly as they come out to the previously made rounds.
Starting isn't so simple as it is with long needles though, but you just whip stitch a bunch and coil it round. The centre ends up being thread wrapped.
If you have really good fine long nettle strands they work well for this, but I made a tea plate sized platter doing this with willow bark and two inch pine needles. It lasted very well indeed.