Did you leave them in the ground long enough for the foliage to yellow and get ratty? If they bloomed at the normal time in the spring and you dug them in the summer, you might have jumped the gun. It's the foliage that feeds and rejuvenates the bulb. If you have decent soil you don't need to fertilize bulbs. When planting you could use a little bone meal or some type of bulb booster, but after that I wouldn't put them on a fertilizing regimen. Sometimes it's just best to treat the fancy (even not so fancy) tulips as annuals.

Tulips in warm climates are a lot of work; digging, chilling, replanting. Unfortunately for me here in a cold zone, although they don't have to be dug up, they put on a good show the first season then gradually disappear over the next season or two. Or they struggle and deer eat the buds and then they gradually disappear. If I wanted tulips, I'm afraid I would treat them as annuals and buy new bulbs each fall.

Your total weight theory is interesting but misleading. Many tulips will produce offset bulbs next to the original, usually called "splits". These will nearly always be too small to bloom for maybe two years if ever. When I dig my tulips after they die back, but before I can't find them, I measure them and only save those at least 12cm in circumference. These will reliably bloom next year. If one third make the grade, I am happy. I store them in a cool dark place in mesh bags loose enough to provide good air circulation. The first of September I will buy new bulbs in quantity, add them to those saved and refrigerate them all in a refrigerator only used for gardening. The first part of December I will plant all the tulips. Those saved will come up and bloom at least two weeks before the earliest new variety purchased. When buying new bulbs I look for a combination of early, mid season and late varieties, buying bags of fifty of each. For less than fifty dollars a year you can have the most stunning spring garden in your neighborhood. Al

This may be a daft question - but how in the world do bulb catalogs keep being able to provide tulips if after time they just 'disappear'?? I don't get it.

Probably not so daft. And I really don't know beyond thinking the commercial grower has the techniques down pat; ideal growing conditions, as well as digging and refreshing and selling their stock on an annual basis. The US is the biggest importer of bulbs - if many of us could plant them once and have them return for generations, perhaps the import volume wouldn't be so high.

A little history: It is a widely-spread misconception that tulips and other bulb flowers are native to Holland. . Nothing could be further from the truth. Almost no bulbous plants are native to this part of the world. The origins of the tulip go back to central Asia - the site of their prime genetic center is in the Tien-Shan and the Pamir Alai Mountain Ranges near modern day Islamabad, close to the border of Russia and China. From these areas, tulips spread to other regions including China and Mongolia to the east and to other regions to the west and northwest. A secondary genetic center developed in Azerbaijan and Armenia (Transcaucasia). From this area, tulips spread to locations which included far-flung parts of Europe.

The tulip's natural habitat is made up of mountainous regions. They are found growing there at very high elevations in the mountains, which means that they are often covered with a thick layer of snow during the winter period. This offers them good protection from the severe cold.

Why the Dutch are so successful is primarily because they've developed - over the last 400 years - a sure-fire system of drainage.

I live in a climate very similar to that described in the quote supplied by duluthinbloomz4 above--or at least it's similar once I supply a bit of regular watering (It's that dry here). I'm at 4500 feet, the temperature swings are very drastic year-round, there is sometimes snow cover, and the air is dry. There is very little natural rainfall here--the average is 7 inches a year. My soil is mostly rocky clay, with rocks over the soil in the drier areas of the garden.

I understand the Dutch not only have developed a perfect drainage system for tulip fields, but that the tulips are subjected to special heat/cold and wet/dry treatments as well as nutrient-rich soil in order to grow up fat bulbs year after year.

While I don't have time to do all that, much less the energy or motivation, I have found that in my climate, even hybrid tulips are fairly perennial. Since I also use quite a few tulips in containers, I remove those tulips after two years in the container and plant the by-then-small bulbs out in my garden. It takes from one to three years for those bulbs to recover to blooming size, and then they generally grow and bloom on a regular schedule, blooming well one year, producing smaller blooms the next, taking one to three years off producing only foliage, then repeating the cycle all over again. I fertilize half-heartedly, throwing spent potting soil all over the flower beds twice a year, fertilizing with slow-release fertilizer twice a year (also just casually hurled in all directions) and adding homemade compost (just garden and kitchen waste thrown in a pile) tossed out all over the beds about every other year. Since I've planted thousands of tulips over the last several years, I can count on a fairly decent, if not Keukenhof-grade show every year.

Species tulips bloom even more reliably for me; they don't ever miss a year.

I've concluded that climate (harsh and dry) and soil conditions (dryish alkaline rocky clay) both contribute greatly to tulip bulb growth and development, and that only the apparently extreme efforts taken by the Dutch growers could ever yield large bulbs on a regular basis.