What Tulips Need to Grow
Gathering Local Spring Tulip Data

— Teacher Background—

Like most plants, tulips need sunlight, warmth, and moisture in order to grow. In the spring, soil, air, and water temperatures rise; snow melts; and rainfall typically increases — setting the stage for plant growth, animal migrations, and other biological changes. All of these seasonal changes are driven by shifts in the amount of available sunlight (called daylength or photoperiod) and its intensity (related to the angle at which it strikes the Earth).

Do tulips all emerge when the soil reaches a set temperature? Will tulips emerge if there's still snow on the ground? Your students' questions won't all have one "right" answer. That's what will make their investigations so exciting!

Here are some interesting things scientists do know:

  • Exposure to cool underground winter temperatures for at least 12 weeks is the most important factor affecting tulip emergence.
  • Daylength is not important for tulips to emerge or bloom. (It does affect many other plants.) But daylength influences temperatures and other factors, which, in turn, affects tulips.
  • Warmer temperatures when tulip flower stems are lengthening result in longer (but weaker) stems. Colder temperatures result in shorter, sturdier stems.
  • Tulips generally won't grow at all at temperatures below 40 degrees.

As you trace all of tulips' basic needs grow back to the sun, students may wonder, What does the sun have to do with rainfall? Below is a brief explanation of the sun-driven water cycle and links to simple activities you can conduct in class.

Water Cycle, 101

Did You Know . . . ?
Water never goes away, but is constantly recycled. In fact, a water molecule in your shower or glass might be the same one that an early ancester used to water crops, or that people in a far away country used to wash clothes a thousand years ago. Stranger yet, it may be one that a dinosaur once sipped!

In the spring, the sun warms water from oceans, lakes, and rivers. Warm water evaporates, turning into a gas called water vapor. Vapor rises. As it does so, it cools off. That causes it to condense — turn back into drops of water — and form clouds. Cool air cannot hold as much moisture as warm air. As the droplets in the clouds get larger and larger, they fall back to Earth as rain or snow. (Sun-warmed air also helps create wind, which helps move clouds and rain.)

You can dig deeper on these Web sites: