We discovered these seedlings as we were doing a schoolyard ecology field trip. In this one spot we found maple seeds – most of the students know these as “helicopter” seeds – in various states, from unsuccessful seeds to seeds that had started to germinate to seedlings that had grown to about 2 inches tall. Not only could we find the seeds and seedlings on the ground, when we looked up into the trees we could see newly forming seeds. It was easy to observe that each tree had hundreds of seeds. We explored how the seeds, when ripe, would be blown about by the wind. Many seeds might end up in bad places like the school roof, the sidewalk or the parking lot where they would not successfully grow. Other seeds might end up in what starts off as a good spot – the lawn, or in the case of our exploration, the flowerbed – where the seed can germinate and start to grow but never become a tree because it would be mowed or weeded out by school caretakers. Still other seeds might end up in a good spot, say in the bushes at the edge of the lawn, only to be eaten by a mouse or a chipmunk, or to sprout into a seedling and be eaten by a rabbit or a deer.
All those seeds – goners! No wonder when we observed the seeds on the maple trees we saw hundreds, probably thousands of seeds. Successful plants, like the Norway maple, produce many seeds each year. Thousands of those seeds never make it, but some will. These will grow into trees that will keep the species going. As a matter of fact, trees like the Norway maple are an invasive species. They are not native to North America. They were planted by people because they do better in urban environments. They are more tolerant of urban pollution so they grow well as a street tree. Over time, their seeds spread about and it does better than other native trees, ending up crowding out the native species. Check any urban park and you will see that the predominant tree growing in the forested areas is likely to be the Norway maple.
Check you schoolyard. There are lots of plants to investigate outside. There’s lots of opportunity to see live, in action, what students are reading about and studying in the classroom.
Can you count the number of seeds here? This is just one of dozens, perhaps hundreds of branches on this one Norway maple, each with just as many seeds. Why so many seeds? When these seeds ripen they will turn brown and fall of the tree.
The wind will scatter them far and wide. One of these seed will end up in a flower bed. It's seems like a great place for the seed to grow. There is plenty of sun, soil and water. Let's see what happens to that seed. We can see that the seed has started to germinate.
The first part of the seedling to grow is the tap root. Here we see that it has sprung from the seed which is still attached to the helicopter wing, called a samara. At this point there are no green leaves or green parts of the plant to produce food so the seedling is using food made by the parent tree that was stored in the cotyledons of the seed. That's why I say the seed is made up of two things, the baby plant and the baby plant's lunch box. First the tap root secures the seedling to the ground and then, to borrow a rhyme from Billy "B" (see Billy "B" link), "the root grows deep, deep into the ground, searches for water and drinks it when it's found"!
As the tap root grows it will send out many root branches, just like the main trunk sending out many branches above ground. Here we can see some of these rootlets. At the end of these rootlets there will be very small root hairs that suck up water and nutrients from the ground that will be used for the seedlings growth.
Here is a seedling that has sprouted and is still connected to the "helicopter" wing. It now has a shoot of growth on the tap root with green leaves. The green leaves are now producing food - "green leaves make food" - that will be used by the seedling to grow.
The end result is this Norway maple seedling growing in a flower bed at the Harmony Hill Elementary School in Cohoes, NY. This may seem like a good spot to grow but not really. The seedling will most likely not become a mature maple tree because it will be removed as an undesireable plant in the flower bed. So what may have looked like a good place to grow ends up a bad place. Many of the seeds from the parent maple will end up in bad places like this, but since the parent tree produces so many seeds some will end up in good places and grow to become mature trees and keep the maple life cycle going.
You can see this story happening in any school or back yard. The life cycle of a tree for all to see and explore.
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