What bulbs are resistant to nibbling and digging by animal pests like deer, rabbits, squirrels?
Daffodils, or Narcissus, are poisonous, and therefore seem to have all-round resistance to nibbling or digging by animals. The ornamental onions (genus Allium) have a built-in repellent as well, with that onion-y smell of theirs. I can attest to many years of experience with nobody bothering those, as I can to the apparent animal-proof nature ofCamassia and most Fritillaria (though I have had skunks dig up the small ones many times while rooting around in the beds here; funny that they’d dislodge skunky-smelling Fritillaria, those skunks).
Hyacinths and foxtail lilies (Eremurus) are also rated for deer-resistance; I cannot offer any first-hand insight, only friends’ reports (and those in catalogs and books).
Do not even think of growing tulips or lilies (Lilium) without protection.
Among the minor bulbs, crocus are, sadly, delicious animal-bait, too (though C. tommasinianus is said to be more resistant than others). Animal-resistant choices include snowdrops (Galanthus); snowflake (Leucojum); winter aconite (Eranthis); glory of the snow (Chionodoxa); Spanish bluebell (Hyacinthoides hispanica); Ornithogalum, Scilla, Muscari (grape hyacinth). The so-called autumn crocus (Colchicum), with its late flowers, are also apparently not tasty.
I have had good success here with all but the true Crocus, though extra-deep planting and a sprinkling of bloodmeal on the soil surface as they pop through is said to deter the incessant digging by chipmunks and squirrels.
Some gardeners enclose delectable bulbs in hardware-cloth “cages” that they fashion as underground dig-proof protective devices.