Pussy willow is of the salix family, so it should not be toxic unless treated with pesticides. Some pesticides are systemic, so a plant can be treated at the nursery and there will be long-lasting pesticides in it for several months after you’ve brought it home. Salix (willow family trees and shrubs) is resistant to a lot of pests though, so they’re rarely treated with pesticides, but some nurseries might use pesticides routinely on everything.

Anyway, salix is safe, but some varieties are highly appetizing for bunnies and bunnies can wreak havoc on saplings. So protect the stems with for example chicken wire (much like you’d do a young fruit tree) until it has become big enough for the buns to not be interested in the stems. They will probably eat the leaves though.

Other hardy plants that are bunny safe is of course all other types of willow, apple trees, hazel, roses (there are Canadian roses and rugosa-roses that are very hardy), hawthorn, sea buckthorne and many more. Again, protect young plants from bunny teeth, if a plant is safe, chances are the bun will want to eat it.