Which Bulbs for You?
Which bulbs will naturalize best for you depends on your climate. Snowdrops (Galanthus spp.) will spread readily in New England but don't receive enough of a chill to bloom even once in Florida. And bugle lilies (Watsonia spp.) form ever-larger clumps in Southern California but wouldn't make it through a winter in Colorado. In regions that get a sufficient winter chill (at least as low as 20°F), daffodils are far and away the most popular choice for naturalizing.
But those versatile small bulbs are excellent choices as well. Try snowdrops, snowflakes (Leucojum spp.), grape hyacinths (Muscari spp.), winter aconites (Eranthis spp.), crocuses, glories of the snow (Chionodoxa spp.), Grecian windflower (Anemone blanda), striped squill (Puschkinia scilloides), and scillas (Scilla spp.).
In warmer regions, bulbs that northern gardeners can grow only by lifting and storing for the winter often spread beautifully: tritonias, corn lilies (Ixia spp.), harlequin flowers (Sparaxis spp.), and freesias.
The one bulb that rarely naturalizes in any climate is the tulip. Most don't stick around for more than two or three years. However, some of the so-called species tulips—the tulips closest to their wild ancestors—will multiply in ideal conditions. One of the most likely to succeed is the lady tulip (Tulipa clusiana). Tulipa tarda, sometimes sold as Tulipa dasystemon, also usually naturalizes well as long as winters are cold.
When looking for bulbs that naturalize, also check the packaging or catalog description. It may be mentioned there. (But don't confuse naturalizing with perennializing. Perennializing means bulbs will return for at least three years. Naturalizing means they return each year and also multiply.)