Dr. Universe: Why do weeds grow sooo fast?

– Leah, 9, British Columbia

Dear Leah,

If you’re like me, you’ve picked up a little dandelion fluff ball and blown the seeds around. Weeds like these make a lot of seeds. They get picked up by the wind and planted far and wide. And as you observe, they grow pretty fast, too.

My friend Tim Miller is a researcher at Washington State University working to help stop weeds from making life difficult for plants we would rather have. Sometimes, weeds are bullies to other plants.

“Weeds are simply plants that are able to compete well with the plants we want to grow,” Miller said. “Imagine two plants growing side by side. Let’s say one is a squash and one is a weed.”

He explained that these plants compete for resources both of them need to grow: sunlight, water, nutrients, and space.

“The weed is able to grab those resources before the vegetable plant can get them, so they tend to grow a little faster and a little better than the vegetable does,” Miller explained.

A race to the top

The weed seeds are already in the garden soil. They wait for just the right temperature and moisture conditions. So, when you plant your seeds, the weeds race out of the ground before whatever you planted can even get started.

Sometimes gardeners help their vegetables by growing them in pots and then transplanting them into the garden. That gives the veggie a head start against the weed.

Miller said some weeds grow from a root that has been alive for many years. These kinds of plants are called perennials. The grasses in your lawn are also perennials. Perennial weeds grow especially fast and are much harder to kill than annuals, which have to grow from seed every year.

Perennial roots have lots of energy in them from previous years of growth. Miller explained that energy helps the shoots grow very quickly. This makes perennial weeds particularly hard to control.

Seeds in the breeze

Dandelions are one kind of perennial. Each dandelion fuzz ball has as many as 100 seeds that travel in the wind. If a dandelion plant makes 10 flower heads, that’s 1,000 seeds waiting to sprout wherever they land. How many dandelions do you think you have in your lawn? If there are 50 plants, just think of those 50,000 new dandelions that can sprout from all those seeds. It’s no wonder weeds are so hard to control.

While they may be bullies to plants, weeds have also inspired some interesting ideas. The engineer who invented Velcro was inspired by those prickly weed burrs that stuck to his clothes and his dog’s fur. You never know what might inspire a great idea or when that idea will strike.

Sincerely,
Dr. Universe

 

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