Teaching Tips for #39 Green Thumbs: Corn and Beans:
Our seeds don't sprout! What did we do wrong?
Commercially packaged popcorn and/or pinto beans may have been sterilized with radiation to increase shelf life, but this kills the seed. Try seeds from a garden or health food store. If only some of your seeds sprout, they are likely too old, or have been stored in a warm and/or moist environment that drains their energy reserves before planting. Additionally, in any batch of seeds, there will be some seeds that simply don't sprout. Seed packages often specify a germination rate (the percentage of seeds that are likely to succeed).
Our seedlings are growing too fast/too slow to match your model answers. How do we adapt?
Without seeing your arrangements, we can only guess. The sprouts may not be getting enough light to develop properly. If this is the case, they will grow "leggy" on long, weak, thin stems that lean precariously toward the strongest light source. The sprouts may also look quite pale.
Classrooms have large windows and bright fluorescent bulbs that usually provide adequate light, but homes are often darker. A south-facing window may help (check sprouts carefully for wilting or sunburn if in direct sunlight). Positioning a desk lamp, either incandescent or fluorescent, as near as possible to the sprouts for several hours a day can also be helpful. Turn the planters around occasionally to correct leaning. If your climate is mild, placing the plants on a porch or patio in dappled shade might help, too, where fresh air and bright light also help discourage mold and mildew. Be sure to monitor plants carefully for drying or overheating.
If plants grow so tall they begin to flop, consider making a string trellis, attached above the window frame with thumbtacks. Tie stems loosely to your trellis to avoid damaging them (young kids will need help). Because this alternative eliminates portability, future observations must happen at the window. As always when doing science, feel free to engineer a solution that fits your circumstances better.
In any event, here's where "cookbook" science gets real. Your experimental results will never be precisely average, especially where growing things are concerned. This can be disconcerting, but it is the nature of, well, nature! Our model answers are the best average we could observe from growing plants in typical classroom conditions in a temperate climate (lots of steady light, temperatures moderately warm during the day and cool at night). If your plants are way ahead of schedule, they're growing in "better-than-average" conditions. If they're too slow, they may be getting less light or warmth than our test sprouts.
Probably the most important thing to remember is this: science is the process of observing what actually happens, not forcing hoped-for results to match an ideal schedule. Scientists develop hypotheses (tentative assumptions) based on what they observe, and then experiment (design ways to interact with their subjects) to check the accuracy of a hypothesis. If it was wrong, they develop and test a new hypothesis. You're doing good science if you're doing these things, whether or not your results match the answer key.
Our plants are growing lots of mold. Should we start over?
Molds and mildews thrive in warm, humid conditions. If this is your situation, try any of the following:
BLEACH! Pre-sterilize containers by dipping in a solution of 10% chlorine bleach and 90% water. If dipping isn't workable, apply generously with a spray bottle or clean sponge. You can also add a couple of drops of bleach to the water in your growing systems. Too much will be toxic to the plants. You can also rinse the seeds for 15 seconds in a 10% bleach solution before you sprout them. Seeds are often "infected" with mold spores before you plant them.
AND/OR: Gently lift the seedlings and replace the paper towels as needed. A fuss, but better than the alternative. You might be able to lift out fuzzy clumps of mildew with a toothpick or a small paint brush moistened with slightly chlorinated water.
AND/OR: Open containers to fresh air and dappled sunshine at times you can keep an eye on them. Monitor the plants for wilting, yellow patches, curled or darkened edges — sunshine can be quite a shock to previously sheltered seedlings. Be sure they don't dry out. You might wish to offer extra credit to a responsible student to monitor the seedlings every hour or so.
NOTE: Because mold and mildew can cause allergic reactions, avoid inhaling them when handling your plants. You could wear a dust mask or scarf over your nose and mouth to minimize your exposure. Finally, if your plants are growing well, they should survive having some mold growing on or around them.
EXTENSION ACTIVITY: Do real science on your own! Study mold and mildew! We've read (haven't tried) that spraying seedlings with CHAMOMILE tea discourages mildew on new seedlings. Other kitchen SPICES, such as thyme and oregano, may help, since they are a traditional means of keeping food from spoiling. A weak solution of the widely popular TEA TREE OIL, dispersed in water with a few drops of liquid hand soap, might be very effective. A solution of BAKING SODA (sodium bicarbonate), about one teaspoon per pint of water, has recently been found to fend off certain mildews in the garden. Spray lightly and monitor closely, though, since too much sodium can be deadly. And the latest scoop from the horticultural world is that MILK misted on plants inhibits some garden pathogens. (It could foster others, though, so stay observant.)
If you come up with any great results, we'd love to pass them on to others, so be sure to let us know!.