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Wintertime can mean many things: snow, holidays, winter break … and bare-branched trees, brown and leafless, as far as the eye can see. Except for those hearty evergreen trees. Firs and pines have those needles that stay nice and green all year round. Today we’re going to do a test on some evergreen branches to see just how hearty they really are.
Materials
- 6 mason jars (clear glasses will work as well)
- 6 short evergreen branches, with the needles (about 6-8 inches long)
- Water
- Coffee
- Vinegar
- Vegetable oil
- Dish soap
- Post-it Notes
- A pencil
- A spoon
Process
- Go out for a hike somewhere where there are some evergreen trees. Find some thin branches that you can reach and break off their tips, so you have six short little branches.
- Enjoy the rest of your hike.
- Go home.
- Line up your mason jars. You’re going to be filling each of them with a different substance to see how the branches react to them.
- Label each of your jars with the Post-It Notes: Air, Water, Vinegar, Coffee, Vegetable Oil, and Soapy Water.
- Leave your “Air” jar empty to see how the branch does with no liquid nourishment.
- Put a few inches of water in your “Water” jar.
- Put a few inches of vinegar in your “Vinegar” jar.
- Put a few inches of coffee in your “Coffee” jar.
- Put a few inches of vegetable oil in your “Vegetable Oil” jar.
- Put a few inches of water in your “Soapy Water” jar and mix it up with your spoon.
- Place one of your branches in each jar, with the cut end in the liquid.
- Over the next week or so, observe any changes in your six samples. How do they react to the different substances they’re soaking up? Do any of needles start to turn brown and fall off?
- You can try this again with new branches and different liquids. Try things like sugar water, salt water, soda, soup broth, milk or anything else you can think of.
Summary
Evergreen trees are really cool. Their needles are actually a special type of leaf, adapted to cold temperatures. But let’s back up a bit.
Leaves are green because plants perform photosynthesis: they make their own food using sunlight, water, and carbon dioxide. To perform photosynthesis, they need a special chemical called chlorophyll. Chlorophyll makes leaves green. For trees with big, wide leaves (the kind we normally think of as leaves), photosynthesis slows down in the fall and stops entirely in the winter, which causes the leaves to die and fall off of the trees. The trees can survive the winter just fine and regrow their leaves in the spring. This type of tree is called deciduous.
Evergreen trees are different. They are called coniferous. They are native to northern areas of the Earth, where winters are longer, colder, and dryer than they are further south. If they went dormant in the winter like deciduous trees, they might never bounce back in the short spring and summer. Instead, their needles are leaves that are curled up really, really tight, and covered with a waxy coating. This allows them to store water from warm, wet seasons to use during a long, dry winter.
How did your branches do? You may have noticed that coffee seems to not harm the branches at all, while vinegar and soap (depending on how much you added to the water) aren’t so great for them. This is because evergreens thrive in soil that is slightly acidic. Coffee is slightly acidic, while vinegar is very acidic, too acidic for most evergreens. Soap is basic, which is the opposite of acidic, and is not a good environment for evergreen trees.
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