There are many great reasons to take an old picture frame and turn it into a terrarium:

If you want a terrarium but you don’t have much space — maybe you live in a dorm room, a small apartment, or you just don’t want to clutter your work surfaces — then hanging a terrarium on your wall (which could be under-utilized space) may be very appealing.
The picture frame terrarium is also a great terrarium solution if you want something inexpensive — picture frames at thrift stores (where there are usually tons to choose from) are typically $1-$4, and the other materials you’ll need are probably things you already have.
Not to mention, you can customize it however you want. You can pick a picture you like as the background, and decorate the frame itself with fingernail polish, stickers, or whatever!
Plus, making a picture frame terrarium is a great way to reuse/upcycle/recycle an old, unused picture frame in an age when pictures are increasingly digital.
Lastly, but maybe most importantly, it’s been found that having plants around your work space makes you more productive!

So if any of those reasons sound appealing to you, then this project on making a picture frame terrarium may be the perfect ‘ible for you!

While I’d never heard of/seen a picture frame terrarium before pursuing this project, I did get inspiration/help from these other terrarium projects, which I essentially remixed to make this one: Tiny Terrariums and Teeny Tiny Terrariums.

Step 1: Materials You'll Need

You’ll need these inexpensive parts to make a picture frame terrarium:

A deep picture frame. It should be about $1-$4 from a thrift store. See Step 2 for details.
A background picture, such as from an old National Geographic magazine. More details in Step 4.
White school glue
Small paint brush to spread the glue
Ruler
Optional but possibly useful: Shipping tape, utility knife, pliers, nail polish, plastic straw, food coloring
Heavy duty water repellent spray (a silicone sealant). These are often used to keep camping gear dry.
Hot glue gun
Small plastic bag, like a sandwich or sealable bag
Scissors
Small rocks. I used some leftover, colorful aquarium gravel I had.
Potting soil. The type of soil you use depends on the plants you use. Most house plants will grow well with regular potting soil, but do some research on the plants you’re interested in.
Medicine dropper or plastic pipette. This is for watering the terrarium. A medicine dropper can be purchased in the pharmacy section of most grocery stores (<$1).
Plants or plant seeds. Depending on how wet or dry you make your terrarium different plants will work. In my terrariums I’ve found that spider plants, coleus cuttings (with roots), Virginia creeper cuttings (with roots), and moss works well (so I don’t keep them super wet). You can make coleus or Virginia creeper cuttings by cutting off a small part of another plant (about 10 cm long at most) and keeping the cut end in water for about a week – roots should start to sprout. A great book that may give you more ideas about what type of plants to use is Terrarium Craft: Create 50 Magical, Miniature Worlds.
Optional decorations: Sticks, pretty/larger rocks, plastic figurines, etc. Make sure they are not wider than the picture frame!

Step 2: Picking Out a Picture Frame

Picture Frame Types

There are two general types of picture frames you’ll typically find: (1) metal-framed ones with a backing that slides up and down, and (2) wooden or plastic-frame ones with metal prongs that are bent (or turned) to hold the backing in place. In this Instructable, I use one of each type to show how either could be used as a picture frame terrarium. I think the metal-framed ones are generally better suited because they seem easier to water-proof and there are no potential issues with wood warping from water, but they seem rarer than the other type.

Picture Frame Depth

For a picture frame terrarium, the larger the frame the better, with depth being the key dimension. The frame should have an open space (between the glass and the back of the frame) that is at least 1.75 cm (about 0.7 inches) deep. (You may need to take the frame apart to see exactly how large this space is.) I used one frame that was a little shallower, around 1.5 cm deep (not shown in this Instructable), and while it does work, it doesn’t give the plants much room. The metal-framed terrarium in this Instructable has an open space about 1.75 cm deep while the black, wooden-framed terrarium has a space about 3.5 cm deep.

Overall Size

Aside from the depth, the overall size of the picture frame really depends on how much space you have on your wall and how large of a terrarium you want! The picture frames I use in this Instructable are 16.5 by 16.5 cm and 15.5 cm by 21 cm. I wouldn’t recommend using a picture frame much smaller than these because then there’s not much space for the plants (leaves and roots). But if you use a large picture frame, be sure you have a good way to securely attach it to the wall by the frame (not the frame’s backing – that won’t be as secure) because it will be a bit heavier with damp soil in it!

Price

Picture frame are typically pretty cheap at thrift stores, which is where I got these. (There’s usually a great selection of frames at thrift stores.) I bought several frames to try out and most were $1 to $3 – the ones in this Instructables were $3 (the metal-framed one) and $4 (the black, wooden-framed one).

Step 3: Preparing the Picture Frame

Carefully take apart the picture frame, being especially careful handling the glass (there are often some broken corners). Clean the glass (on both sides) with some Windex and a rag – it’ll be hard to clean the inside later! Look at the different parts of the picture frame, thinking about how will be the best way to seal the bottom of the frame so that water doesn’t leak out (I’ll show the different approaches I used in the next steps). Toss out any cardboard inserts that you don’t want to use. Also figure out what part will be the top and what will be the bottom – for the metal-framed picture frames, you’ll want to flip them upside down so the enclosed top is now at the bottom, where it will help keep water from leaking out.

Step 4: Attaching a Background Picture

Adding a picture to the back of the picture frame terrarium is optional, but I think it makes a big difference – it gives the terrarium some real character.

Picking a Background Picture

My only recommendations are to pick something that is not too dark (otherwise it makes the whole terrarium look rather dark) and pick something that is not too busy with many different colors (because then it can be hard to make out the living plants from the busy background). This is just based on my experience making picture frame terrariums. I recommend going through some colorful magazines, or pick a picture frame with a picture you already like. For the metal-framed picture frame, I found a cute praying mantis picture from a National Geographic magazine and used that. For the black, wooden-framed picture frame, it came with a picture of a. artichoke flower cross-section, which I kept.

Attaching the Picture

Figure out how you want the picture positioned on the backing (if it didn’t come with the frame). You may want to tape the edges of the picture lighting on to the backing to keep it in position. Cover the front side of the backing with white school glue, then use a small paint brush to smooth out the glue (preventing bumps in your picture) and place the picture on it.

Step 5: Planning the Terrarium

You may want to plan how you want your terrarium to look when it’s done. Specifically, you’ll be filling it with layers of sand, small rocks, and potting soil, and then arranging plants, sticks, and other decorations on top. I found it helpful to plan out the space within the picture frame since space is limited.

Planning the Layers

Trace the useable space of the picture frame onto a sheet of paper. Then use a ruler to mark and draw the different layers. I recommend putting a layer of sand on the bottom, somewhere around 1 cm to 2.5 cm high. The sand will help keep some moisture in the terrarium, and will hold the small rocks in place. Right above the sand, make a layer of small rocks, somewhere around 1.5 to 2 cm high. The rocks (and sand) will let water drain from the soil and keep the soil (and plant roots) from getting water-logged. Right above the small rocks, make a layer of soil, somewhere around 2 to 3 cm high. See the pictures in this step for examples. I recommend planning the layers next to the backing picture you’ve picked so that you can see how the layers will end up blocking parts of the picture.

Planning the Plants and other Decorations

On top of the sand, small rocks, and potting soil, you’ll be putting plants and maybe some moss, larger rocks, and other decorations. You may want to look at the size of your plants, etc., and figure out how they’ll fit in this top space. See my pictures here for examples. Of course, you can change things around later (and I did).

As I recommended before in the materials section, a book that you might find useful for planning your terrarium is Terrarium Craft: Create 50 Magical, Miniature Worlds -- super helpful book for terrarium beginners and experienced individuals!

Step 6: Water-Proofing the Picture Frame

To water-proof the picture frames, I sprayed all interior parts with heavy duty water repellent spray (this includes the inside of the main picture frame, the cardboard/wooden backing with the picture on it, and any other interior surfaces except metal and glass ones). This spray didn’t damage anything I sprayed it on – the pictures seemed just fine, and water resistant! I used two coatings for everything, letting them sit a few hours between the two sprayings. Be sure to follow all safety warnings when using the water protection spray!

Step 7: Sealing the Bottom of the Picture Frame

Now that the interior surfaces of the picture frame are protected from water, you’ll want to start closing up the picture frame while making sure the bottom is sealed completely so water doesn’t leak out when you water your terrarium.

Gluing the Glass to the Frame

If there’s space for the glue in the frame, I highly recommend using hot glue to glue the bottom part of the glass to the picture frame to seal that area shut. I was able to do this for the metal-framed picture frame (but not the other one) and I think it helps a lot. See the pictures in this step.

Using a Wooden/Plastic-Framed Picture Frame

Because of the wooden insert in the black, wooden picture frame, I didn’t have space to glue the glass to the frame (but wish I had!). Instead I used some shipping tape and taped it along the bottom of the insert, slid that snugly into place in the frame, and sealed the backing shut on it. I didn’t completely seal it because I still needed interior access, so I made sure I could still tilt the backing outwards. See the pictures.

Using a Metal-Framed Picture Frame

For this type of frame, I think it’s best to make a small hole in the backing, somewhere near the top, so that you can easily access the interior still. I did this by using a utility knife to cut the hole, and then I disguised it with nail polish. Basically I coated the edges in nail polish and turned the hole into the middle of a flower (see the pictures). I made a few other nail polish flowers on the picture to match this one, and I think it added some nice color to the picture. Then carefully slide the picture into position (making sure the nail polish has dried!) and seal the bottom of the backing shut by hot gluing it to the metal frame.

Step 8: Preparing and Adding the Sand

Preparing the Sand

Any sand you want to use is probably just fine. To match some of the colors in my terrarium, I tried dying the sand bluish-purple using a lot of food coloring (about 1+ tsp blue and red food coloring). It took more food coloring than expected, but was quite pretty. So if you want some color, give it a try, and make sure to let the sand dry before adding it (it’ll look different when dry). Also, the food coloring will leak out of the sand, so be careful when getting it wet (especially while testing the terrarium for leaks)!

Adding the Sand

Take a plastic bag (sandwich or sealable-type) and cut off a small tip of one corner, as shown in the picture above. Put the sand into the un-cut corner, and place the cut-off corner into the terrarium (by opening it slightly or using the hole you made in the backing). The pour the sand through the cut-off corner and into the terrarium. Gently tap the frame on a hard surface to let the sand settle into a horizontal layer. Use a ruler to measure the height of the layer and stop when you’ve reached the height you want, based on your planned design (if you made one).

Step 9: Preparing and Adding the Small Rocks

Preparing the Small Rocks

Basically, pick out some pretty rocks that you think will look nice in your terrarium. Make sure they’re small enough to easily fit inside. See what they’ll look like dry versus damp. I used small gravel pieces from an old aquarium and some polished (green) glass from a beach I’d collected.

Adding the Small Rocks

For the wooden-type picture frame, I carefully tilted the backing outwards and poured the rocks in through the opening in the top (see the picture). For the metal-framed picture frame, I used the hole in the backing to pour the small rocks into the frame. Gently tap the terrarium on a hard surface to have the gravel settle into a horizontal layer. Use a ruler to measure the height of the small rock layer and stop when you’ve reached the height you want, based on your planned design (if you made one).

Step 10: Adding the Soil

As you did with the sand, use the plastic bag with a cut-off corner, place the soil in the un-cut corner and place the cut-off corner in the terrarium, and then pour the soil into the terrarium through the cut-off corner. Gently tap the frame on a hard surface to let the soil settle into a horizontal layer. Use a medicine dropper (or plastic pipette) to add water to dampen the soil – this will make the soil compress so you’ll probably find that you need to add more soil. Use a ruler to measure the height of the soil and stop once you’ve reached the height (of damp soil) that you want, based on your planned design (if you made one).

WARNING: At first, only add water to the terrarium over a sink or rags in case the terrarium leaks, especially if you used food coloring in the sand, since the water that comes out may be dyed!

Step 11: Adding the Plants and Other Decorations

Get your plants ready and figure out how to arrange them within the remaining open space of the terrarium. Then add them in. A plastic straw is very helpful for moving plants/decorations around and into place in the picture frame terrarium.

If you are using a wooden-framed terrarium, add these parts by carefully tilting the backing outwards, as you’ve been doing, and sliding them inside. (If you get any rocks/debris blocking the backing from closing, use a straw to carefully blow them out of the way.) If you’re using a metal-framed terrarium, add these final parts through the hole you made in the backing.

If you get dirt on the glass, just use the medicine dropper to wash the glass clean with some fresh water.

Step 12: Watering the Picture Frame Terrarium

Keep the wooden-framed terrarium sealed shut by bending the metal prongs closed against the backing. When you want to water this terrarium, bend the prongs outwards, carefully tilt the backing outwards, and squirt water down onto the plants using the medicine dropper.

For the metal-framed terrarium, water it through the hole in the backing (using a medicine dropper).

For the first few days, you’ll want to water the plants every day. This will help the terrarium soak up some initial moisture. Then you’ll only want to water as frequently as those plants need watering – keep an eye on the soil to make sure it doesn’t get too dry.

Step 13: Hanging the Picture Frame Terrarium

If your frame already has a hook for hanging, then use that. Just make sure it’s attached to the frame, and not the backing (which may come out/loose). My wooden-framed terrarium already had a wire that I used for hanging. For my metal-framed terrarium, I bent an existing frame hook I had so that it could slide under the top of the metal frame – I centered the hook, put a dab of hot glue on it, and glued it to the frame there.

Make sure your picture frame terrarium is hung in a location where it will receive a lot of indirect light, but no direct light – this could heat it up too much!

Wherever you put it, enjoy your new picture frame terrarium and showing it off to the people who will surly ask you about this unique wall decoration!