After last week’s rhubarb ruminations, I wanted another excuse to talk about one of my favorite not-really-fruits. I love introducing kids to rhubarb by telling them I’m going to let them taste a poisonous plant. It really focuses the attention of a group of excited 9 year olds when they think it’s a life-or-death situation. And it’s true, while the stems are delicious, the leaves are poisonous to humans! They are high in oxalic acid, which in large doses, can cause kidney problems, and even death. Oxalic acid is actually present in small quantities in a number of vegetables, including sorrel, spinach, and chard, but nothing close to an amount that would make you sick. Rhubarb leaves have a lot more oxalic acid, but an adult would still have to eat at least 4 kg of the leaves to reach a lethal dose, and, well, they’re just not that tasty.
Potential lethality aside, rhubarb is fun because it’s one of very few food that we treat like a fruit, but isn’t – it’s a stem! Fruits and flowers and even roots get a lot of attention, but I feel like stems don’t get the love they deserve. Stems give plants their structure and shape and carry water and nutrients up from the roots, and energy in the form of sugars down from the leaves. They are like a plant’s skeleton and circulatory system combined! So let’s hear it for the stalks, spears, vines, canes, and trunks out there, just going about their business without a lot of fanfare, bringing us all the beautiful plant life around us.
Here are five ways to explore stems this week.
Dissect a Stem
One of the many important things a stem does is carry water from the roots to the rest of the plant. Inside the stem are structures called xylem which provide a path for water, and the nutrients it carries, to help flowers bloom, make fruits juicy, and give leaves the water they need to make sugar through photosynthesis. Sugars from the leaves flow down the phloem that surround the zylem. In the stem of a celery plant, the xylem are big enough that we can see them easily with just a couple of kitchen tools.
You can try this with other stems, too. I had some success with asparagus, and I suspect bok choi would work really well, too. Experiment with the stems you have in your veggie drawer!
Celery Dissection Activity Guide
See How Stems Work
But how do those xylem actually get the water up from the roots? Plants don’t have a heart like we do to pump water around, and water always moves downhill because of gravity, right? Plants have found a gravity loophole, called capillary action. It’s the same thing that happens when you dip the end of a paper towel in water and the water soaks upward. In this video, my friend Cinders, a children’s librarian in London, uses capillary action to make water walk and create a rainbow, and shows you how you can do it, too!
Walking Water Rainbow
Learn a Stem’s Story
Some plants have massive stems that can live for hundreds or even thousands of years! Yes, we’re talking about tree trunks, and every tree trunk has a story to tell. Check out the video from SciShow Kids for a quick intro to how tree rings can tell us a story, then try the online Tree Cookie game from Wonderville and Learn Alberta!
Life as a Tree Video
The Tree Game
Explore Dendroclimatology
Tree rings are important tools for scientists studying global climate change, both to document a history of climate over thousands of years, and to help us understand the changes happening around us today. This activity for older students uses two videos to explore what dendroclimatology is and how the stories told by trees are shaping our knowledge of climate, touching on not only science and technology, but geography, industry, and careers as well.
Dendroclimatology Activity Guide
Make a Three-Stem Dessert
I couldn’t do all that talk about the glories of rhubarb without leaving you with a rhubarb recipe! Now, I love rhubarb cake, pie, crisp… I even had a great rhubarb danish recently. But if you want a quick rhubarb fix, nothing is easier than a compote. Some people call this “stewed rhubarb”, but compote just sounds fancier. And, because we’re all about the stems, this recipe has not just one, but three different stem foods! Granulated sugar is processed from sugar canes, maple syrup comes from the sap of the maple trees. Both of these types of sugar are pulled out of the phloem in the plant’s stems! And, of course, we have the tart rhubarb. Want to add a fourth (!) stem? Add a pinch of cinnamon! Cinnamon come from the inner bark of the cinnamon tree.
This compote is great still warm over ice cream, or try it in a yogurt parfait with some granola for breakfast. Or if you, like me, are on the sourdough baking bandwagon, top some sourdough waffles with this goodness. (Freezer waffles work great, too!)
Rhubarb Compote Recipe
Stay sturdy, and drink your water!
Kat
