A greenhouse is defined as an enclosed space that is heated and lit by the sun. Short-wave solar radiation passes through a layer of transparent or semitransparent material, and heats up surfaces like the ground and plants inside the greenhouse.
Making your own greenhouse is great for growing your garden and for teaching educational concepts in a hands-on way. In NYC, not everyone can have their own standard-sized greenhouse, but that doesn’t mean you can’t have a tiny one!
You can supplement this in-class or at-home activity with science, social studies, and math curriculum. The scientific greenhouse effect is the clearest curricular connection. But did you also know some of the earliest accounts of using structures to grow plants date back to ancient Rome, around 30 A.D., where members of the cucumber and squash family were grown for the Emperor Tiberius? Find this info and more in the Greenhouse Manual for Educators from the United States Botanic Garden.
Below, check out 4 models of Tiny Greenhouses you can build!
Model 1: Egg Carton Greenhouse
This model is great for germinating seeds. The extra warmth trapped inside will help your seeds germinate faster than they would on their own. Once they sprout, you’ll have to take the lid off in order for the seedlings to keep growing up!
• Cardboard or plastic egg cartons
• Gardening soil (seed starting soil mix preferred)
• Your choice of seeds- vegetable or flowers
• Permanent marker
• Sharp item (nail, box cutter or small knife)
Step 1: If using a cardboard egg carton, find an upcycled plastic bag or plastic lid to use as a cover. If using a plastic carton, you have a built-in lid!
The plastic lid for the carton will serve as a mini-greenhouse and heat your seeds up enough for them to germinate outside, even in cooler weather.
Step 2: Poke holes at the bottom of each cup, to provide drainage and prevent seedlings from drowning. Also, poke some holes in the top for a small amount of air flow.
Step 3: Add soil to the egg cartons! The soil should be slightly damp.
Step 4: Add 3-5 seeds in each little cup, following the planting instructions on your seed packet.
Step 5: Using your permanent marker, make sure you mark what day your seeds were planted and how many days it should take for them to germinate. Keeping track of this is especially important if you are doing multiple types of seeds in one carton.
Step 6: Spritz them with water to make the soil saturated, but not drowning, then cover with the lid! Water every couple of days to make sure the soil doesn’t dry out.
Model 2: Greenhouse in a Bag
These mini-greenhouses are good for germination purposes. Each student can keep track of their own seed start. Of course we hope to one day live in a world without plastic bags, but for now, reusing baggies to grow plants is one way to upcycle. Minimum equipment for maximum germination! These sprouts are also a fun window decoration if you use painter’s tape.
• (Re-used!) Ziploc bag
• Potting soil or paper towel
• Spray bottle or measuring cup
• Permanent marker
• Masking tape, sticky notes, or labels
Step 1: Add a few spoonfuls of moist soil to the bag, or a wet paper towel.
Step 2: Add seeds (3 seeds or more to increase germination chances)
Step 3: Close the bag, tape it to a window, and label it with the date and type of seeds.
Note: No need to water the soil since the moisture is trapped inside the bag. The sun heats up the air inside the bag - just like a greenhouse!
Model 3: Plastic Clamshell Greenhouse
• Upcycled, clear plastic clamshell containers with a top and bottom (see photo above)
• Newspaper or tissue rolls
• Tape or label
• Popsicle stick or pen to prop container open when it starts sprouting (see photo)
For tissue roll seed starters - Cut the toilet paper roll in half. With each half, make four vertical cuts in the roll, 1/3 of the way up. Fold the cut area on the bottom like you would close a box. Now your pot has a base! The little pots should be short enough that you can put them in the container and still close the container.
For newspaper roll seed starters – You’ll be making a newspaper mold of a can. You can use a small can, a shot glass, or a small jar. Cut the newspaper into long, wide strips, then wrap the can multiple times over with the newspaper strip. Fold the edges of the newspaper over the can and work your way around in a circle until all the edges are folded over firmly. Then remove the can and you have a newspaper mold of it!
Step 1: Create your rolls for your seed starting
Step 2: Poke a few holes in the plastic tray for drainage.
Step 3: Moisten your soil lightly and fill the rolls with soil.
Step 4: Plant the seeds in the soil according the package’s instructions.
Step 5: Place your rolls into your plastic container in a sunny spot. Close the lid. Label each roll with the type of plant and day it was planted.
Step 6: Allow the seeds to germinate. Once you see it sprout, prop up the lid of the plastic container to allow the sprouts to keep growing.
Note: When the seedlings get taller, you’ll need to transplant them to a bigger pot or in the ground. Make sure you completely remove the toilet paper roll cardboard before planting. The cardboard doesn’t break down easily in all soil. For the newspaper pots, you can bury them completely and the newspaper will decompose.
Model 4: Plastic Bottle Greenhouse
This greenhouse model will allow you to grow the seedlings higher than the previous models. You can grow them until they have about 3 sets of true leaves, and then transplant them into the ground or a large pot. As shown in the second photo, you can use just the top half of the bottle to create a greenhouse effect over a potted plant, or even place it around a seedling already in the ground.
• Upcycled Plastic Bottles
• Box cutter
• Seeds or seedlings
Step 1: Wash out the bottle with soap and water thoroughly.
Step 2: Cut partly across the bottle 4-5 inches above the bottom of the bottle. Leave the upper part of the bottle attached to create a hanging lid.
Step 3: Place soil into the bottom of the bottle. Moisten your soil but don’t soak it.
Step 4: Plant your seedlings or seeds in the soil and label them.
Note: You can control the humidity inside the bottle by leaving the cap on or off.
Follow up activities:
Measure growth, temperature, and other observations of the greenhouses. You can make charts and graphs.
Compare germination rates of seeds started in a greenhouse versus seeds started without one.
Draw pictures of the plants changing.
Check out this lesson plan on Desktop Greenhouses from New York Agriculture in the Classroom
Transplant your greenhouse sprouts to a larger pot or in the ground once they have about 3 sets of leaves or outgrow the mini greenhouse.