As all good gardeners know, daffodils are dependable “repeaters”, perennials that return year after year with more and more blooms.

But tulips are somewhat different. The tulip, for all its spectacular beauty, is one of the easiest flowers to grow successfully in the garden. Plant a bulb in fall and even a novice gardener can expect to see a beautiful flower come spring. But getting a tulip to perform well in the second or third year is another story.

The tulip - as duly noted in horticultural texts - is a perennial flower. This means that a tulip should be expected to return and bloom year after year. But for all intents and purposes this isn't always the case. Most tulip-lovers content themselves with treating it as an annual, re-planting again each fall.

But if tulips are perennial, then why don't they always behave as perennials? The answer to this pressing horticultural puzzle is surprisingly simple.

"Tulips are indeed true perennials," explains Frans Roozen, technical director of the International Flower Bulb Center in Hillegom, the Netherlands. "Getting them to bloom in your garden year after year is no problem, if your garden happens to be located in the foothills of the Himalayas, or the steppes of eastern Turkey."

According to Roozen, the tulip - an oriental native first introduced to the western world some 400 years ago - is at its perennial best in conditions that match the cold winters and hot, dry summers of its native regions. When asked how they have managed to thrive in Holland, one of the wettest countries on earth, he smiles and says, "That takes a bit of know-how."

The Dutch Touch

Roozen explains that Holland's sandy soil, and the proven ability of the Dutch to perform miracles of hydraulic engineering (meaning they can get water to do just about anything they want), actually offer some of the most excellent growing conditions for tulip bulbs on the planet. To get the bulbs to not only return but to multiply (sort of a prerequisite for supporting an ongoing industry) is a bit more problematic.

"Professional Dutch growers subject their plant stock to an ingenious series of heat and humidity treatments each summer before planting," explains Roozen. Developed over the past 400 years, this manipulation of temperature and humidity levels allows growers today to perfectly replicate the tulip's native habitat."

By the time the bulbs are tucked into the sandy Dutch soil for their winter's sleep (and Mother Nature's "cold treatment") the bulbs have been fooled into thinking they've been through another summer drought in the Himalayas!

This is why Dutch growers always have scads of tulip bulbs to sell each fall, and the rest of us, left to our own climactic devices, have dwindling stocks.

"Don't try this at home," warns Roozen, "the process for temperature- treating bulbs is quite tricky, requiring years of experience and expensive climate control systems such as the ones you see in Dutch bulb sheds."

How Home Gardeners Can Get Top Performance from Tulips

For Americans who would like to get top performance from their tulips, Roozen provides the following simple tips and guidelines.

• Choose tulips that are marked good for "naturalizing" or "perennializing."
• Generally species or botanical tulips and their hybridized strains are a good bet. These are cultivated bulbs that have not been extensively cross-bred and thus are very close to the bulb as found in nature.

Though cross-breeding or hybridizing sometimes diminishes a tulip's ability to "perennialize," other times it enhances this ability. Among hybrids that perennialize best are all the Darwin Hybrids in red, rose, orange, yellow and two-tone colors. Emperor tulips and some Triumph Tulips also perennialize well. All “species” tulips, the wild ones, are totally perennial, as are many of the “minor” bulbs including crocus.

• Plant bulbs in a well-drained area. This is always good advice for planting bulbs, and is essential for naturalizing or perennializing. Wet soil promotes fungus and disease and can even rot bulbs. Adding organic matter such as well rotted cows manure, compost or peat moss can also help facilitate drainage.
• Plant tulip bulbs deep -- about eight inches deep, measuring from the base of the bulb. Note: If you add mulch to the surface after planting, include its depth as a part of your overall planting depth. (For instance, 5 inches deep in soil plus 3 inches of mulch = 8 inches deep.)
• Water bulbs after planting. Though standing water is not good for bulbs, sufficient water is necessary to get them growing. Water is especially important right after planting to ensure that the plants develop a strong root system before going into winter dormancy.
• In the spring, after the blossoms have passed their peak, clip off the flower heads and allow the green foliage to die back. This technique lets the plant put all its energy into building a strong bulb for next season.
• Fertilize in fall and spring. For those who treat tulips as annuals - as many gardeners do with great success and satisfaction - no fertilizer is necessary. Healthy Dutch bulbs (which are not seeds, but living plants), have more than enough food stored up to ensure a vigorous bloom the first season. But if a come-back performance is desired, low nitrogen fertilizer such as well-rotted cow manure, or special bulb fertilizer is recommended at fall planting time and each fall thereafter. If you did not fertilize in fall, in spring, as the shoots first appear, you can add a high nitrogen, fast-release fertilizer can help promote future performance.

Following these simple guidelines will increase the success of many homeowners in improving the repeat performance of their tulips.

But regardless of whether it's the magnificent crop of color from the first year's planting, or the slightly diminished but still lovely stand of flowers planted a few years back, the tulip remains one of the world's best loved flowers. And fall is the time to plant them.