I purchased and planted 500 Darwin Hybrid tulip bulbs from a commercial grower in the fall of 2013. Spring of 2014: a beautiful array of blooming tulips! Following this blooming period, I waited for leaves to yellow and wither and then cut them back. I also added bulb food, per package directions. Spring 2015: Out of 500 bulbs, only one bloomed. Lots of leaves, but only the single bloom. I'm wondering if there's any reason to hope that next spring they'll rebound, or should I assume the entire 500 need to be replaced? Thanks for any insights you might have.

Tulips can be finicky. They tend to not have the same perenniality that narcissus do. Having them come back successfully is a gamble. The secret to getting more years of bloom from them include having a good, loose, well-drained soil, planting them deeply, and feeding them after flowering. Oftentimes, once they have flowered, they expended so much energy that there is little left in the original bulb. Part of the success is starting with good size bulbs. What each company sells will vary. Smaller bulbs are often less expensive. Park districts and public gardens treat them as annuals because it is rare to have the entire planting come back the next year and put on the same display. An exception to the 'annual treatment' is that species types tend to be more long-lived. I don't think you should expect them to rebound next year.

I read (after I planted four dozen of them) that nearly all tulips have been exposed to a type of virus or bacteria that eventually kills the bulb a year or two after planting and that even varieties that are more resistant still die after three or four years. Except for one variety I planted called "Flair," that is in its seventh spring, all the rest of mine were dead after two years.

I'm not aware of a treatment that exposes them to viruses except for the ones that have streaking where the virus gives the 'fire' like coloration. See above post - tulips, for the most part, do not have longevity because the original bulb is depleted of food reserves. Cultivar/type, depth of planting, soil type all influence how long they live.