Create an Early Spring
In the dead of winter, it's hard to imagine the stage is already set for flowering trees and shrubs to burst into bloom. Your students can grab a glimpse of spring, and explore how plants grow and adapt to their environment, by coaxing buds on bare branches to come to life in the classroom.
Deciduous trees and shrubs form their flower buds the previous summer or fall and then enter a period of leafless winter dormancy. Because actively growing plants can't withstand freezing temperatures for an extended period, they have adapted by "resting" during the coldest months. After six to eight weeks of outdoor temperatures between about 32 and 40 degrees F, (by January in many areas), most trees and shrubs have met their dormancy requirements. When the weather warms, sap begins to flow, buds swell, and leaves and flowers emerge. By providing the same late winter/early spring conditions in the classroom that entice flowers and leaves to emerge outdoors, students can force branches to reveal their spring finery.
But the lesson doesn't have to stop there. Your young sleuths can observe twigs to see what they reveal about plant growth, buds, pollinators, and more. Or they can experiment to find the ideal conditions for coaxing blooms. Mid-winter bouquet gathering can also inspire investigations of the practice of pruning. The Curriculum Connections section offers details on these ideas and more.
Once your class has identified the woody plants they want to coax into bloom (see list below), you can head out to do some pruning.
Exacto knife or hammer (optional)
deep container (e.g., bucket or tall vase)
trees and shrubs (see list, below)
Procedures for Coaxing Blooms Indoors
1. Have students select shrub or tree branches with scads of flower buds, which tend to proliferate on younger branches. Here's your first opportunity for inquiry. Challenge students to try to figure out which branches are youngest, and then explain their thinking. You might next tackle the question of which buds will form leaves and which, flowers. (Flower buds tend to be a bit more plump.) Hard to tell? Students may want to dissect some with an Exacto knife or simply make predictions and mark buds, and then keenly observe them over time.
Good candidates for forcing blooms include:
Early-flowering trees and shrubs (cut in late January to February) - ash, azalea, birch, elm, forsythia, hazelnut, maple, mulberry, redbud, plum, pussy willow, sumac
Later-flowering trees and shrubs (cut in late February/March) - apple, cherry, crabapple, dogwood, elderberry, honey locust, honeysuckle, magnolia, mountain ash
2. Use sharp pruners to cut 1- to 2-foot sections of branches about six weeks before they'd naturally flower in your area. If you're not sure of local flowering or leafing-out times, students can research what blooms when. They might interview community members, check with the local Cooperative Extension Service, or consult Internet sites. Or your young scientists might experiment by trying to force branches cut at different times. Since swelling buds are also indicators of readiness to bloom, students might want to check a few branches weekly beginning in January.
3. Make sure the branches quickly absorb water. First, use one of the following methods: 1) Scrape a 3-inch strip with a knife or scissors along the side of the stem near the bottom, 2) Use an Exacto knife to cut an X into the base of the branch, or 3) Use a hammer to gently crush the end of the branches. (Students may want to compare methods.) Next, place the branches in lukewarm water for a day or, if possible, submerge the whole stems in water overnight.
4. Put the cuttings into a container of cool water and place it away from heaters and direct sun. Invite students to mist the branches daily to simulate spring rains and keep the buds moist and full. Change the water and cut an inch off stems each week.
5. Move the cuttings to a bright location when the buds open in three to six weeks. (The timing will depend on the types of branches you use and when you cut them.)