Greenhouses extend the growing season by providing a sheltered location from cold temperatures. Seedlings can be started before the last frost in the spring or brought into the greenhouse to continue growing past the first frost in the fall. A small greenhouse doesn't have to be time-consuming or expensive to start.
Place the baker's rack in a southwest corner next to the house or a building where it will receive the most sun for the longest time during the late fall and early spring months.
Cut the clear plastic sheeting in a panel the width of the back of the rack and long enough to go from the ground up the back of the rack to just over the top. Cut another panel of sheeting as wide as the side of the rack and long enough to go from the ground on one side of the rack over the top and down the other side of the rack to the ground. Cut the last panel of sheeting as wide as the front of the rack to go from the ground in front of the rack up to the top.
Sew the side and back panels together to form a three sided "tent" that slips over the rack. Sew the front panel to the top of the tent, but leave it free on the sides. This front opening is how you tend to the plants once they are inside. Place the tent on the baker's rack.
Punch holes into each side of the front panel where the shelves are located. The front panel will be twist-tied through the holes to the shelf to close the tent or mini greenhouse up and retain the heat.
Place two or three bricks on each shelf of the rack. The bricks absorb heat during the day and release it through the night when temperatures drop. Filled plastic water jugs wrapped in black plastic have the same effect. The sun shines on the black plastic and heats the water.