Seedlings are a fragile lot. Cold will stunt them, wind can break them, and evaporation can wilt them. In that vulnerable stage of their growth, young plants need extra protection from the elements. The ideal solution? Grow seedlings in a greenhouse. Here are a few of my favorite DIY mini greenhouse ideas that won’t break the bank.
Why a Mini Greenhouse?
Obviously, a full-scale greenhouse isn’t very practical for hobby gardeners. It’s way out of my budget, and I don’t have the space for it.
Your local garden center probably offers portable greenhouses. But these can be quite pricey, and they’re one-size-fits-all. It might not fit on your balcony or your little bit of lawn.
But what about a DIY mini greenhouse?
There are many ideas on the Web to pick from. Don’t worry if you’re not a carpenter or handyperson: many of these are simple enough to build with your kids.
That way, you can use whatever materials you have on hand for a solution that’s perfect for your needs, budget, space, and plants.
Below are a few genius ideas for you to try. Remember that these are just a few guidelines: let your imagination inspire you.
Tomato Cage Wrapped in Plastic
Let’s start with the simplest idea: wrapping a tomato cage in plastic cling film.
This solution is very portable. You can use it indoors or outdoors, and move it around as necessary. Just plop it over the plant that needs shelter or extra humidity, and voilà. It’s also adaptable. Any cage-like structure can be wrapped in any flexible transparent membrane, like clear plastic bags or bubble wrap.
Make sure to poke a few holes in the plastic to provide some aeration. You can also leave a little space between the ground and the bottom of the makeshift greenhouse for air to circulate.
This option is ideal for balcony or patio gardens, and can help to extend your growing season.
Recycled CD Cases
If you have lots of CD cases gathering dust, you can give them a new life as a mini greenhouse. If you don’t have two dozen cases lying around, ask your family and friends to donate theirs. It’ll be an environmentally friendly community gardening project, right in your living space.
Here’s What You’ll Need:
- 24 CD cases to recycle. I recommend that you gather a few extras in case you break some or mess up with gluing. It’s also much easier if they’re all the same size. Avoid the slim cases, as they’re more fragile and less stable.
- Hot glue gun and lots of glue. Get more glue sticks than you think you’ll need, trust me.
- Tape (masking tape, duct tape, packing tape, whatever you have handy).
How to Build a Greenhouse with Old CD cases:
- Remove everything from the cases so that all you have left is clear plastic. Recycle the insert with the lyrics, as well as the black plastic disc holders.
- Build two pairs of identical walls. The first pair is 2 cases wide by two cases high, and the long walls are 3 cases wide by 2 cases high. Keep the cases closed and glue them end to end. That way, you end up with double-paned walls that have extra insulation against the cold. The cases are rectangular, not square, so make sure to keep that in mind before you glue it all together.
- Build the top. Take 4 cases and open them up. Now, glue the sides together, but be careful not to glue the hinges. You want the whole top to still move around the hinges. That will be the door.
- Put it all together. Put the walls up, using tape to hold them together while you work. Then, glue the edges. Remove the tape once the glue has dried completely. Finally, glue the top. The top is wider than the box. You can leave it like that, or you can shorten one of the halves of the top. Measure and mark the top against the walls, then use a hobby knife to score the cases.Score both sides for cleaner breaks. And don’t forget to score the lips of the cases to avoid messy break lines. Make sure the hinge faces down so you can open the “door” upwards. Glue the shorter half on top of the box.
Raised Bed with Hinged Window
If your garden is composed of raised beds, a little addition can transform them into cold frames.
By adding a transparent roof on top of the bed, you provide extra wind protection for the plants. Also, the roof will trap heat inside, keeping plants and soil warm during the cool days of spring or fall. This solution works best for shorter, cold-hardy plants like spinach, lettuces, or kale. It also works best on raised beds with higher sides.
My favorite solution is to add an old framed window to your existing raised garden bed.
Here’s what you’ll need:
- Enough wood-framed windows to cover your raised bed(s)
- At least two hinges per window
- Enough screws for the hinges
- Exterior paint or stain for the window frame
- Weather stripping or foam (optional, but recommended for colder climates)
- Double-sided tape or hot glue (for the weather stripping or foam)
- Sticks or dowels of varying lengths (to keep the roof open on hotter days)
Here’s how to transform your raised bed into a cold frame:
- Measure your raised beds. You want your windows to be as wide as the frame of the raised bed, or wider. A quick trick is to align one side of the window with the frame. The other side should be flush or longer than the frame.
- Paint or stain the window frame, and make sure to use a product made for outdoors. That window will be the barrier between your plants and the elements, after all. Allow ample time for the paint or stain to dry before moving on to the next step.
- Marl the window for weather stripping (optional). Put the window on the raised bed and use a marker or chalk to mark the window where it meets the bed. That’s where the weather stripping or foam will go.
- Install the weather stripping or foam on the window (optional). The idea is to create a flexible seal between the top and the raised bed. The better the seal, the better insulated your cold frame will be. And for those in colder climates, better insulation allows you to start your seedlings earlier in spring and extend your growing season later into fall.
- Install the hinges. Use enough screws to solidly fix the window to the frame.
- Cut sticks or dowels to size. Use these to keep the roof open on hotter days or to control humidity levels. Simply jam the stick between the window and the garden bed. For extra solidity, you can drill a shallow hole in the bed and in the window frame where you’ll install the sticks when needed.
Upcycled Glass Door Cabinet or Glass Display Case
If you want to make the best possible use of the space you have, it’s a good idea to go vertical. Stacking seedlings or plants on shelves allows you to cultivate more plants per square foot. An upcycled glass door cabinet is perfect for that. This solution works best for seedlings and small potted plants.
The best glass door cabinets for a DIY greenhouse have glass doors, glass sides, and glass shelves. That way, you significantly reduce the amount of shade in the greenhouse. Obviously, plants on higher shelves will throw shade on the lower shelves. Keep that in mind when placing your plants in the cabinet. Put sun-loving plants on top and shade-tolerant varieties on the bottom.
You can find these cabinets in garage sales, flea markets, or even on the side of the road, ready for the dump. Keep an eye out for online garage sales and swap sites. You’d be surprised at how easy it is get a nice unit for practically nothing.
Cabinets to Look For
If you find a glass cabinet with a metal frame, you’re in luck. It should need minimal prep work, especially if it’s made of aluminum or galvanized steel. If it’s rusted, just sand the frame down, then apply a coat of outdoor metal paint. Make sure to cover the glass panes with newspaper and painter’s tape during the painting process.
A wooden frame might need a bit more work, but it’s still worth the effort. Prep the wooden frame with a light sanding, then apply a few coats of outdoor paint or stain. Allow lots of drying time before sheltering your plants in there. The last thing you want is for nasty fumes to seep into your spinach or poison your orchids.
As I mentioned earlier, there are many different ideas out there on how to build your very own mini greenhouse. Look at what materials you have on hand and search online for ideas on how to use them most effectively. Did you come across an inspired build? Let us know!