This instructable will be a quick guide on building a small cheap/free greenhouse for starting your plants. We will use 2-liter size contour Coke bottles and some around the house materials in this project, although other size/shape bottles can be used.
Step 1: Gather Materials
As with the first step in most projects it is important to gather your materials beforehand. For our Coke bottle greenhouse we will need:
1. Coke Bottle or some similar clear plastic container. (personally we prefer a container with a screw type top to make watering quick and easy.)
2. Rubbing Alcohol. (used to remove label adhesive)
3. Cotton Balls. (used with alcohol to make label removal easier)
4. Paper Towels. (for cleanup of excess alcohol and label remnants)
5. Knife/Scissors. (we used a combination of both for cutting the bottles.
6. Soil. (Many types can be used depending on your choice of plant species, we will use Miracle Grow brand potting soil)
7. Plants or Seeds. (Most any type of plant may be used in this project, but we will be using hot chili pepper seeds (Trinidad Scorpions))
8. Clear Packing Tape. (other tapes can also be used, but we prefer clear for aesthetics.
9. Spray Bottle. (this item is optional but makes watering and maintaining your plants much simpler)
Step 2: Clean the Bottle(s)
This step is relatively quick and easy. After removing the contents of your container (hopefully by drinking them) we will want to give the bottle a quick rinse to remove any remaining liquids. The best method for this would be to remove the top and add a little water to the bottle, maybe 1/8 to 1/4 full then replace the cap and give the bottle a good shake. Afterwards pour the water out. Depending on the contents of the bottle you may need to repeat this a few times.
Step 3: Removing the Label
This step will likely be your most time consuming. While it is not necessary to remove every last bit of the label it will make your project look nicer in the end. The method we use to remove labels is to peel as much as possible off by hand then use the rubbing alcohol and cotton balls to loosen the adhesive that holds the label on. After a good soak with alcohol use your fingernail or some other hard object to scrape away the adhesive and remaining label. (We used a knife on this step but you must be careful doing so or it could result in a cut.) If you choose to do so you may simply peel as much label as you can by hand, in which case you will not need rubbing alcohol or cotton balls for this project.
Step 4: Cut the Bottle
For this step our preferred method is to use a sharp knife to make an incision on the bottle then use scissors to complete the cut. This is nice because scissors allow you to make a cleaner cut and do any needed trimming with minimal risk of danger. Please be aware that once you start cutting the bottle it will lose much of its structural integrity and become increasingly difficult to cut. Scissors make the process much easier. For our project the bottles we chose had small indented lines around the center of the bottle, this helped to make a straight cut across the bottle. If your bottle does not have this it may be helpful to first draw a line in marker on your bottle before cutting. We also chose to cut small triangle shapes on four sides of the top bottle half this made four roughly equal size tabs we could use to push the bottles back together. There are many methods to accomplish this so you may need to experiment a little to find the best way to fit your bottle halves back together before filling with dirt.
Step 5: Adding Soil
For this step we just want to add some decent quality potting mix to the container. Depending on the type of seeds/plants you intend to grow your desired mix may change so its a good idea to do some research before you choose a soil. Or if you are trying to keep cost minimal with this project and have decent quality soil it may be ok to simply dig some from your back yard. As we live in an apartment and are choosing to grow hot pepper plants (Trinidad Scorpions) we chose a soil that drains very well as pepper plants typically do not like "wet feet."
Step 6: Planting Seeds
Although we neglected to take good pictures of this step it is fairly straight forward. You will want to take your seeds and place them into a small hole in the dirt of your mini greenhouse. The hole should not be very deep, somewhere between 1/4 and 1/2 inch. The best method for this is to simply take your finger and press a small indentation into the soil then insert the seeds and cover over with soil. Once again this may vary slightly based on the seeds/plants you are using so make sure to do a little research on your particular species.
Step 7: Closing the Greenhouse
This is the last step in our little project. It could be the most difficult if you did not test fit your bottle halves together. The method we chose as described earlier is to cut small triangles on the bottom cut edge of the top bottle half. Doing this will create tabs that can be pushed inside the bottom bottle half one at a time until the bottle is completely inserted into the bottom half. After this is completed it may be a good idea to put some tape around the seam to make a better seal. Any tape will do, but we chose clear packing tape for aesthetic purposes. The very last step to our Coke Bottle Greenhouse is to open the screw top lid spray in a few sprays of water with a spray bottle, reclose the lid, and place in a sunny area outside or in a window sill.
Step 8: Maintenance
Remember to check on your new plants regularly to ensure they are getting the proper amounts of sunlight and water. For our Scorpion peppers they prefer temperatures above 70 degrees with lots of sunlight and water usually twice weekly as they can be over watered. Once sprouted and several leaves have formed we will remove the top halves of our greenhouses and use the bottom as a simpler planter until the peppers are ready to be relocated to a bigger home. Maintenance is where your experience will vary most based on the plants you chose to start in your new mini greenhouse so once again be sure to read up on the species you chose and learn as much as possible.
Step 9: Even Tinier Bottle Greenhouse (Bonus Step)
A similar method can be used on a smaller scale by using a 16 or 20oz plastic bottle. This size is great for starting plants from seeds and takes up very little space so can be used just about anywhere. For the pictured version we used the bottom portion of two 16.9oz water bottles and friction fit them together (no tape used). A single bottle can be used more similar to the described 2-liter version if you wish to have the scew top on this size as well. Although different species vary we use this size to start our hot peppers. The best method we have discovered is to take two folded pieces of paper towel dampen them and then place several seeds in between the two pieces of folded paper. Once you place the lid on you should not need to water until the seeds start to sprout. Just place your tiny greenhouse in a warm area and check back in about 5-7 days to look for sprouts.