Grow Your Own: Seedling Success
By: Eve Pranis
Once your students have created visions and plans for bountiful outdoor gardens, the next step is bringing them to life. If you're in an area with a short growing season and/or you want to harvest certain crops before school is out for the summer, you can get a jump on the season by raising your own seedlings. You may also want to start seedlings indoors if you've planned a community beautification project, spring plant sale, or if you plan to bring plants to senior centers, homeless shelters, or send them home as gifts. Raising seedlings in the classroom offers a good opportunity to practice reading and language skills (via seed packet planting instructions), math skills (e.g., using seed packet information to determine when to plant), and science process skills (predicting germination times or inferring why seedlings are leggy).
Your students' first challenge will be to determine when they'll want to have seedlings ready to give away, sell, or plant outdoors. To develop a planting calendar, they'll need to know:
- the average last spring frost date in your area (check with local gardeners, the Cooperative Extension Service, or the weather service);
- the time required from sowing each type of seed to transplanting it outdoors (check seed packets);
- the time from transplanting to harvest if you want to harvest at a particular time (check seed catalogs and packets).
Students can check seed packets or gardening catalogs to find out about frost tolerance, then count back to decide when to plant each crop, and develop a planting calendar. While investigating planting dates, students may also want to find last frost dates for different areas of the country, and discuss why the dates vary. Or they might research the origins of some garden plants and discuss how their temperature preferences may relate to where in the world the plants originated.
Containers. Many types of containers will work, as long as they're at least 2 to 3 inches deep and have drainage holes. To save space with seedlings that are easy to transplant, you can sow seeds closely in shallow containers (try recycled containers like milk cartons), then transplant them later to larger individual containers or sections.
Soil. Use home-mixed or premixed soilless potting mix for starting seedlings, since it is light, holds water, and is weed-free and sterile. Although your students may want to experiment and compare soilless mix with real soil (and should be encouraged to do so!), garden soil does tend to harbor weed seeds and fungus, and is often too heavy for tender seedlings.
Light. Although you can grow seedlings on windowsills that get plenty of light (south-facing windows are best), these seedlings tend to be "leggy," and will generally grow better under fluorescent lights. Seedlings grow best with 14 to 16 hours of light a day, much more than windows can supply in late winter. To prevent stretched, leggy stems, the lights should be kept within a few inches of the top leaves.