Sunday, May 15, 2005

What Is Special About Dandelions?

You've probably seen dandelions before: yellow flowers which turn into white fluffy spheres. But, despite these interesting flowers, the part of the plant that the dandelion is named after is actually the leaf! The sides of dandelion leaves have a zig-zag shape because they have very deep dents in them. This zig-zag shape reminded early Europeans of lion's teeth, so they called the plant "dent-de-lion," which means "lion's tooth" in Old French! The name "dent-de-lion" then became modernized into "dandelion."

Although dandelions originated in Europe, they were brought to many other regions of the world and now can be found virtually anywhere! This is because dandelions can survive and thrive in many different environments, including some that are harsh enough to kill most plants. In other words, the dandelion is one tough plant!

In fact, the toughness of dandelions makes them very hard to get rid of. If you simply pull off the leaves and flowers, the plant will regenerate (re-grow), much like a starfish can regenerate if it loses its limbs.

As for the flowers, they are actually composed of many tiny flowers arranged in a circular bunch, which is typically 1 to 2 inches wide. This is called a composite flower. In fact, each composite flower of a dandelion is made up of hundreds of tiny individual flowers! This explains why each composite flower can produce hundred of seeds (one per flower).

Another example of a composite flower is the sunflower. The difference (other than size) between sunflowers and dandelions is that the small flowers in the middle of a sunflower look like little buds. They are greenish-brown instead of yellow and do not look like they have petals. These central flowers are called disk flowers.

The outer flowers (the ones that are bright yellow) are called ray flowers. Dandelions are unique in that they are completely made up of ray flowers. In other words, they don't have any disk flowers. This is why all of the flowers in a dandelion look the same.

Another unique characteristic of dandelions is that they don't rely on insects to carry pollen from one flower to another. This process is called fertilization, or cross-pollination. In contrast to most plants, dandelions can fertilize themselves. This makes it even easier for them to reproduce, making them even better weeds!

Furthermore, the seeds have a unique way of spreading themselves around. You have probably noticed that dandelions become white and fluffy after they have bloomed. In fact, this transformation from the yellow composite flower to the white "snowball" form can occur overnight!

Later on, some of the "fluff" blows away in the wind. These fluffy pieces are actually dandelion seeds being carried by tiny white "parachutes" which float well in the wind. This helps the plant to spread its seeds over a large area, which makes it more likely that some will land in a nice patch of soil and be able to grow into new dandelion plants.

Little Lion Experiment:

To see just how effective these "parachutes" are, find a dandelion in its white fluffy form, and pull off the fluff. Pull slowly so that the seeds stay attached to the fluff! Then collect some similar-sized seeds (basil seeds work well for this). Now that you have two sets of seeds that are similar in size, shape, and weight, you can be relatively certain that any differences in how far the seeds travel will be due to the dandelion's parachute (rather than its size, shape, or weight).

Go outside on a windy day and toss the basil seeds up into the air. Watch them fall and notice how far (horizontally) they travel form where you are standing. Do the same with the dandelion seeds. Notice how much further they travel.

Now, can you see why dandelions sprout up in odd places such as cracks in the sidewalk? You don't see basil plants growing there! Seeds that travel far and wide are able to end up in environments much different than those in which they started. So, if you had a basil plant and a dandelion in a garden, where would you expect to find the next generation of basil plants? Where would you expect to find the next generation of dandelions?