Why evergreens stay green

But why? How are they able to stay green while deciduous trees oaks, maples, birch, etc. Both evergreens and deciduous trees get their green color from chlorophyll, which is required for photosynthesis, the process which plants use to make their food. It requires both sunlight and water. In the fall, when days get short, and less sunlight is available, deciduous trees lose their chlorophyll, the green fades, and the color show begins.

But the chlorophyll also has another important job. The chlorophyll absorbs sunlight which the tree can use to turn carbon dioxide from the air and water into sugars.

It is these sugars that help the tree grow and stay green. But while some trees, such as maples, stop doing photosynthesis in the colder months, evergreens keep on photosynthesizing pho-toe-synth-uh-size-ing. In addition to sugars, evergreen trees also need something called mineral nutrients to help them grow. In fact, humans also need mineral nutrients, such as calcium, potassium, and iron to help them grow.

But while humans get their nutrients from food, trees get a lot of their own kinds of nutrients from the soil. Evergreens store up all those nutrients and can use them through the winter months. So why are they able to stay green while deciduous trees oaks, maples, birch, etc. Every year, new needles grow and old needles drop. This time of year, you'll see new growth — those are needles that are lighter green coming out at the end of the stem.

Evergreens put needles on in groups and they tend to lose them in these same groups. It's kind of like your hair — all of your individual hairs have a cycle of growing and falling out, but they don't all fall out at the same time.

Evergreens usually keep their needles for two to three years. If you see red needles that are closer to the stem, those are the ones that are getting ready to drop.