2 Liter Greenhouse

A cheap and easy way to make a mini greenhouse for tropical or other plants, or perhaps a small isopod house! This project is great for adding a little low-maintenance color to your room or space. Depending on the plant used, you will likely have to move up to a larger container, but these are great for starting out plants, getting them past their most delicate phase before moving them to an outside garden. If you like the idea of growing a fancy tropical plant but don't have a garden or climate to make it happen, this might be a fun project for you!

2 liter soda/beverage bottle, empty and rinsed (3 liter would be even better if you can find them...)

Cutting device (scissors, box knife, etc)

Heat source (hair dryer, heat gun, etc)

Potting soil

Water

Seeds of your choice

Optional: hydrogen peroxide

Simple enough, you just cut the bottle to the length you want, plus a little overlap. If you want the bottle to be the same size, just cut the top off just under where the sides of the bottle become straight (not the curved part, we'll go over why in the next step).

SAFETY NOTE: As a reminder, always be mindful of cutting tools, how you use them, and where your hands are in relation to the cutting tool. Starting a cut on the outside of a bottle like this can be a bit tricky, and when the cutter pops through the layer of plastic can be a dangerous situation if your hands are in the wrong place.

Like mentioned above, there will be a little overlap between the two pieces. This is so when the pieces go together, they make a seal, keeping moisture in and bugs & mold spores out (blech!). To get the pieces to slip together, a little heat applied to the top piece (just around the sealing edge) will cause it to warp and shrink slightly, creating the slip fit.

SAFETY NOTE: We're mixing heat sources and a meltable, potentially flammable substance. Be gentle with your application of heat to avoid risk of fire and burns, you don't need to actually melt the plastic, just let it warp a bit. It will be hot once you are done, so be sure to keep that in mind when you are finished.

SAFETY NOTE: I would not recommend using a lighter or any other naked flame as the chance of burning or setting the plastic aflame is high. Flaming plastic melts and drips, sticking to things and either spreading flame or causing nasty burns.

Like mentioned above, not much heat is necessary, a hair dryer will suffice and is easy to aim as well. Take your time, and rotate the bottle, only warming the very edge, never heating one spot for long. When done, the edge will be a bit wavy and will have contracted slightly. It can now be slid into the bottom part. It might still be tight fit, but a little wiggling or another round of heat will likely take care of it.

The reason we want the top to slide into the bottom is that when the whole thing is sealed, moisture will often be running down the top and sides of the bottle. With the top slid into the bottom, the joint acts like shingles on a roof, and the joint stays dry. If it were the opposite (top slid over the bottom), moisture would collect at the joint, either trapped in a pool between the plastic or possibly leaking out and making little puddles.

Another simple step, just add the amount of potting soil you think you'll need, which will depend on the plant and how soon/if you plan on transplanting, and the seeds. The amount of seeds and how deep they go in will depend of what you plant and if they will need a bigger container.

Another step you can take that may not be necessary (I have always done it just to be safe) is to add hydrogen peroxide (the normal 3% concentration you find at any store near the pharmacy area) to the potting soil and mix until dampened and spray some on the insides of the bottle. This is just to kill any stray mold spores that may try to contaminate your teeny garden. Remember, depending on what you plant this will be a sealed, high humidity environment! I would do this before adding seeds as the soil will warm considerably as the peroxide does its thing.

SAFETY NOTE: Ok, it's not too scary, but be sure to read the warnings on the bottle before using peroxide (or any chemical that has warnings associated with it), and try to keep your eyes safe from getting splashed. I've heard that some with sensitive skin can get slightly irritated if splashed peroxide is left in contact with the skin, so you might want to rinse it off if it gets on you.

Now comes the part where it gets kind of boring for awhile before the excitement starts. Depending on what you planted, it could be a several days or couple weeks before anything pops up, but be patient! The avocado tree in the pictures took between a week and a half and two weeks before I saw anything pop up. Months have passed, and I have not had to do anything other than place the containers near sunlight or a grow light. I suppose if it looks like things are getting dry inside you might have to open the lid on top and add a splash of water, but thus far the seals have held well and I have not had to.

The above pictures are of some kiwi plants and a avocado tree. Mixed in with both are some dragonfruit plants that I thought had died from an earlier attempt using an open-topped container. I dampened the soil with peroxide and planted the kiwis and avocado in separate 2l containers, and later on I noticed dragonfruit plants sprouting alongside the kiwis and avocado tree! Oddly enough, looking at the side of the bottles, I can even see some little dragonfruit plants growing under the soil; dragonfruit must not be as delicate as I thought.

Once your plants get tall enough, you might need to add more height to your container. This easy enough to accomplish; just cut the bottom off of another bottle as before (on the straight sided part), then cut the top off of the bottle, but just above where the bottle begins to curve in (see the line on the picture of the Sunkist bottle). The new middle section is ready to add between the existing 2 parts of the container you already made, no need for a hair dryer even! Just pop off the top, add the new section (keeping the curved side down), then put the top back on.

This is just a little extra tidbit on getting some tropical plants started. I liked the idea of growing something tropical as the fruits are often yummy, and there's no need to cold stratify! For whatever reason cold stratification has always ruined my efforts to grow cherry and almond trees from seeds; darned if I know why.

For the kiwis and dragonfruits, I just washed any fruit remnants from the seeds by rubbing them inside of a damp paper towel, poked the seeds roughly 1/4 to 1/2 inch under the potting soil before sealing them up, and like magic they began to grow. It was wonderfully simple. To get the seeds I just lightly scraped the inside of a cut kiwi with a spoon, and the same for the dragonfruit. There are lots of seeds in there, you'll quickly end up with more than you need!

You can let the seeds soak in water or leave them in a wet or damp paper towel and they will quickly begin to sprout (some of the dragonfruit seeds in the picture were starting to sprout the next day!), but this is unnecessary. Apparently dragon fruit seeds will sprout and start to grow even if under a few inches of soil (once again, thought I had killed the seeds in a failed effort to grow them in an open-top container, so I reused the soil for kiwis; now there's a bunch of dragonfruit cacti in my kiwi container :p), though it's slow going from there.

The avocado was similar, I washed the pit, and placed it pointier side up under about 1/2 inch of the soil. After close to 2 weeks I saw it sprouting. If I find a way to keep my avocado tree growing, I'll likely graft to it to get some delicious fruit from it. Hope you enjoyed the tutorial, and if you get some mini plants growing, post pics in the comments!