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If you have been following Growing With Science, you know that we have been closely observing the insects on a small planting of zinnias for the last few weeks (posts about zinnia insects 1, 2, and 3).

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The variety of zinnias we have been observing are Profusion® Fire, which are hybrids between regular zinnias (Zinnia elegans), and the Mexican or narrowleaf zinnias (Zinnia angustifolia).

While initially observing the insects on the plants, we also noticed something about the plants themselves, specifically the flowers. Do you notice anything about the flowers in the photograph above?

As it turns out, the flowers change as they become older.

tightly-closed-zinnia-bud-63The zinnia flower head starts out as a tightly closed bud.

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When the flower head first opens, it is deep, bright orange, almost scarlet.

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As the flower head matures, it becomes a medium orange. Do you see any other changes?

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The oldest flower heads have faded to almost yellow. They look a bit worse for wear.

There have been some changes to the flowers within the flower head as well, but we need to learn some vocabulary before we can investigate it.

Flower Parts

 

Mature_flower_diagram.svg

(“Mature flower diagram” by Mariana Ruiz LadyofHats. Public Domain image at Wikimedia Commons.)

You may have seen a diagram like this one describing the various parts of a hypothetical flower. Basically, the ovary, style and stigma form the female part of the flower that receives the pollen. The stamens, made up of filaments and anthers, are the male parts of the flower that produce pollen.

Very few flowers actually conform to this simple diagram, and the zinnias are certainly much more complex. Rather than a single flower, what we see is actually a cluster of minute flowers called disk and ray florets.

 

young-floret-parts

You may have to scroll back up to the bigger photographs above to see the parts clearly, but in the young flower head the ray florets around the outside are flowering, which is evident by the yellow stigmas. Only a few disk florets in the center have begun to open.

 

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In the middle-aged flower head, most of the ray florets have finished flowering and many of the disk florets around the outside have begun to flower.

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In the older flower heads, the outer florets have finished flowering and are developing the all-important seeds. Only the disk florets at the very center are still flowering.

Flower Part Dissection Activity for Children

Note: check whether the children have severe pollen allergies before starting this activity.

Gather:

  • Living flowers of different types (see flower notes)
  • Safety scissors and other dissecting equipment (age appropriate)
  • Diagrams/illustrations of flower part with labels
  • Dissecting microscope (optional)
  • Paper (optional)
  • Pens or markers (optional)
  • Tape (optional)

Flower notes:  Tiger lilies or other lilies are excellent examples of simple flowers as seen in the diagram. Daisies and sunflowers are good examples of the complex flowers. Working with a large group? You might want to ask your local grocery store or florist if they would be willing to donate flowers that have passed their freshness date. Keep the flowers alive in a vase of water.

Have the children observe the different types of flowers closely. Provide diagrams or illustrations naming the flower parts. Once everyone has had a chance to observe the flowers, allow the children to dissect the flowers to examine the parts more fully. Very young children can simply pull them apart. Older children might use safety scissors. Still older children can use dissecting pins and a dissecting microscope, if available.

Remove the petals or pull off the ray florets. Can you find the stigma? What about the stamens? Is the stamen releasing pollen? What color is the pollen? What is inside a disk floret?

Older children might want to spread the parts onto a piece of paper or card stock and tape them down. Label the parts.

Extension:  If the flower parts aren't damaged too badly, allow the children resemble the parts to make their own mix of "Franken-flowers."

Resources:
The Clover & the Bee; A Book of Pollination by Anne Ophelia Dowden

This image does not do this beautiful book justice. It includes many highly-detailed, scientifically-accurate diagrams of different types of flowers with their parts labelled. It also discusses pollinators and how they use differently-shaped flowers in different ways. Super scientific reference for educators and older children.

Age Range: 10 and up
Hardcover: 90 pages
Publisher: HarperCollins; 1st edition (May 1, 1990)
ISBN-10: 0690046774
ISBN-13: 978-0690046779

This is an older book by the same author which covers similar material.

Publisher: Ty Crowell Co (June 1963)
Language: English
ISBN-10: 0690506562
ISBN-13: 978-0690506563

 

Disclosure:  I am an affiliate for Amazon. If you click through the linked titles or ads and make a purchase, I will receive a small commission at no extra charge to you. Proceeds will be used to maintain this self-hosted blog.

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If you live in the San Francisco area and are interested in ants, take a look at this post on my Wild About Ants blog about a citizen science project that's being run by the California Academy of Sciences. It's definitely kid friendly.

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Yes, we were in San Francisco last week. We got to see a lot of interesting new things.

Let us know if you decide to participate in the ant study. We'd love to hear what you find out.

Have you seen the new California Academy of Sciences building in Golden Gate Park?

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It has a space age-looking green roof.

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Yes, these are pictures of the actual roof. Any ideas what the gray strips with wire over them are? Here's a close up:

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We were told they are the pathways that allow people to walk through for maintenance or study. The gray rocks are lightweight pumice or lava rock. They could also be for drainage.

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Although we saw different types of plants growing on the roof, the most common are perennial strawberries.

Why would anyone want a green roof? We learned that the roof helps moderate the temperature of the building, creates less water run off during rains, and supplies food for wildlife.

Although green roofs have been around for a long time, these roofs are designed with modern materials and are often used on much larger and more complicated building than in the past. If you like the idea of a green roof, here are some ideas for activities:

1. Research green roofs and then design and create your own small green roof model. Two things to consider are the weight of the planting materials (the lighter the better) and how to make sure the bottom layer doesn't leak. Experiment with different materials and see how long they last. Google Sketch-up is a free software that makes designing easy and fun.

2. Find out which plants are used on green roofs in your area and try growing some in small containers, such as flats. Experiment with similar plants. See if you can find a type of plant, or mix of plants that grow well in roof conditions. Sedums are often popular green roof plants, but my son is trying the ground cover dichondra on his model green roof.

3. See how a green roof changes the temperature of the building it covers. Compare the temperatures inside a box covered with plants versus one with standard insulation versus an uncovered box. Look at the range of temperatures over time, if possible.

4. Look at how much water runs off a green roof versus a conventional roof during a rain storm. Think about how you would test this and design and experiment. Can you collect the run off?

5. Investigate what kinds of wildlife are attracted to green roofs. The California Academy of Sciences' roof had a bee hive on it.

We'd love to hear about your green roof projects.

For more information, try:

Green Roof at California Academy of Sciences

Green Roof Design Lesson for grades 9-12  at Science NetLinks

Research Paper of Green Roofs, which gives history and details for construction