How to Turn a Raised Garden Bed Into a Greenhouse

Building a greenhouse can seem daunting to many gardeners. Traditional greenhouse enclosure complexities and costs aside, the sheer time and effort is enough to turn off most hobbyist gardeners. However, building a greenhouse doesn't have to be a burden. If a simple greenhouse can be built for roughly $20 in materials found at your local home improvement center, isn’t that worth the benefits it provides?

Even the most resilient plants may need protection from the elements. In five minutes, you can erect a greenhouse that will keep your plants warmer during cold spells and lengthen your growing season. The framework of the greenhouse, which we will explain shortly, also serves a dual purpose. When temperatures heat up and sun intensifies, you can use the greenhouse framework as a structure to support sun dissipating material, such as patio screening, and give your garden a reprieve from the summer heat.

Follow along below to see how to build your five-minute greenhouse and establish a framework over your raised garden that can be used to help manage weather and temperature for your garden throughout the year.

Materials for Building a Greenhouse

• 3 10-foot Lengths of Masonry Ladder

These are similar to tomato cages in material and design, just longer and unshaped. It is the backbone of the greenhouse, and its design doesn’t require additional support via twine or garden wire. Three 10-foot ladders is the suggested amount for a 4x4-foot raised garden, six 10-foot ladders for a 4x8 raised garden, and so on.

• 12x12 Plastic Sheeting–4mm Thick

Plastic sheeting costs little and can be purchased in large cuts/rolls. To create a greenhouse in minutes it’s important that the sheet is in one piece. The 4mm thickness is recommended because it is malleable, but rigid enough to semi-support itself and thick enough to retain a garden’s temperature well without blocking off sunlight too much. There are thicker and thinner plastic sheeting options, keeping in mind that the thicker the sheeting the better temperature retention it will provide your garden. However, it will also reduce the amount of sunlight reaching your plants since sheeting is often translucent or opaque. A 12x12 sheet is ideal for a 4x4-foot raised garden, or 16x12 for a 4x8 garden.

• 8-12 Bricks

Gardeners, feel free to be creative here. The bricks are simply used to weigh down the sides of the sheeting material, so they don’t need to be bricks. You can use anything weighty enough to secure the sheeting sides against the boards of your garden. Rocks, sandbags, or something more aesthetically pleasing is perfectly fine as well.

How to Build Your Raised Garden Greenhouse

1. Stick both ends of one masonry ladder into the interior soil of your raised garden flush with the corresponding corners. You will need to start with one side first, and then curve the other side downwards into the ground. It isn’t difficult, but keep your face clear of the pointy ends. The raised garden walls will support the curved masonry ladder thanks to the laws of resistance.

2. Repeat Step 1, except place another masonry ladder over the middle of the garden, and the third at the opposite end of the garden—both parallel with the first curved masonry ladder. When all three are placed, they should run in a parallel row creating a tunnel-like framework.

3. Lay the sheeting over the masonry ladder framework so that each side equally touches the ground. One side should have extra, bunched-up material that will become your makeshift garden access point.

4. Place your bricks or weighted objects along the sides to ensure that wind or animals won’t disturb it’s positioning.

5. When you need to access your raised garden bed under the greenhouse, take the bricks off the side with extra material, and roll it up and out of the way.

6. Once done accessing your garden to care for your plants, pull the extra material back down and reposition the bricks to keep the garden closed off. That’s it!

Greenhouse Framework: It’s Up to You

Because this is such a simple process, you can wholly erect and dismantle the greenhouse when you wish. However, the framework may prove useful enough that you simply want to keep it up. Decorate it during the summer with fun garden trinkets, or place screen material on it to dissipate higher intensity sun rays and heat to cool off your plants. Whatever you do, a DIY greenhouse that costs so little in time and money is worth the benefits.