Plants will always grow towards the source of light, which can be shown by creating a box that a plant will have to maneuver through in order to reach the light. Place a shoebox vertically onto a table top. Use scissors to cut the rim of the shoebox lid. This will leave the top of the box remaining. Place the top vertically in front of you, and cut it into three equal sections horizontally. Cut a 2-inch circle out of each section, placing the hole in a different location or each section. Insert the sections into the shoebox, spacing them out evenly to effectively separate the box into three compartments. Tape the sections into place. With the shoebox standing up vertically, cut a 2-inch hole in the top of the box. Place a small plant in the bottom compartment. Place a piece of black garbage bag over the open face, taping it shut. Place the box by a sunny window. Every two days, lift up one corner of the garbage bag in order to water the plant. After one month, remove the bag to reveal that the plant has grown through the different holes in order to reach the light at the top.
Plants require water in order to grow. This can be demonstrated by germinating a seed without soil, using only water. Soak two paper towels in water until they are sopping wet. Place a few seeds in between the two paper towels. Insert the paper towels with the seeds into a plastic sealable bag. Place the bag in a dark location, such as a closet. After a week, remove the paper towels from the bag to reveal the sprouting seedlings.
Making a bottle greenhouse can teach children that they can create a small environment using water and light in order to successfully grow small plants. Locate a 2 liter soda bottle with a removable bottom cap. Remove the bottom cap and set it aside. This will leave the plastic bottle with a bumpy bottom. Cut off the bottom of the bottle. Fill the bottom cap 1/4 full of charcoal. Fill the rest of the bottom cap full of potting soil. Place a few seeds into the soil, and water the bottom thoroughly. Fit the top of the bottle onto the bottom cap. Place the greenhouse next to a sunny window. After a few weeks, the plants will begin to grow and develop.