Tulips categorized as "botanical" (meaning they have a "Latin" name such as Greigii, Fosteriana, Kauffmaniana) will force well, as will tulips classified as Single Early, Double Early, and Triumph. Darwin Hybrids tend to get way too tall and don't work very well and Single Late,Double Late, Lily-Flowered, and Parrots don't do as well if forced indoors. I grow them in pots outside all the time--but have been less than thrilled when I've tried them inside.
