Bureau of Land Management Learning Landscapes

What's Wrong With This Picture?

Invasive Weeds: A Growing Pain

Many weeds have pretty flowers but they are a growing pain. They crowd out native plants, harm animal habitats and increase erosion.

Seed Bank Lab *

By germinating weed seeds in random soil samples, students can see that there are large numbers of seeds stored in the environment. For example, a knapweed plant can produce an average of 1,000 seeds per plant. Four percent of the seed might germinate, leaving 96 percent in the seed bank. A seed bank is made of seeds that have not yet germinated and are stored in the soil. The seeds of many plants remain viable in the soil for many years until conditions are ripe for them to sprout. Have students do the following: Collect soil samples from different areas. Milk cartons can be cut to make containers for this. Try not to disturb the surface of the soil. Water the samples just enough to keep the soil moist but not too wet. Keep a record of collection date and when seeds sprout. Remove sprouts over 2 inches high to make room for more sprouts. Ask the students if they can identify the emerging plants.

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Last Updated: June 2006