From Seed to Seed:
Plant Science for K-8 Educators

Digging Deeper

Exceptions to the Rules

Some weeds, such as dandelion, can produce more than one generation in a growing season. Their life cycle may be just a few months. On the other hand, the agave, or century plant, may need to grow for up to 20 years to accumulate the energy reserves necessary to produce its 20- to 40-foot seed stalks. Even more remarkable, some types of bamboo are thought to have life cycles of more than 100 years. It may take them 100 years to flower and then they won't flower again for another 100 years. Of course a life span this long is difficult for scientists to verify.

Just to muddy things up a bit: Many of the plants that northern gardeners grow as annuals are really perennials when grown in their native climates. Examples include petunia, geranium, tomato, and pepper. And some plants like hollyhock are really perennials, but most people treat them as biennials because after the second season they usually succumb to disease.

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