Greenhouse Dreams

Greenhouse Dreams: Peppers in December

Peppers in December

A home garden greenhouse may seem like a daunting item on a gardener’s wish list. It comes in the form of a pipe dream or is shuffled into the “one of these days” category.

Greenhouse dreams typically resurface when coming home from a weekend adventure to find freshly emerged seedlings on their deathbeds. Sometimes they can be coaxed back to life and other times they are beyond revival, but these young phyto-children could have been saved with a simple DIY greenhouse.

A greenhouse provides plants with a head start by sheltering them from whatever the weather is up to outside. Greenhouse gardeners can sow seeds weeks before the topsoil is warm enough for outdoor germination. And late-season producers can keep fruiting beyond their outdoor counterparts. With a temperature-controlled environment, a wider variety of species, which would otherwise be intolerant of the climate on site, are available. In addition to supreme growing conditions, herbivory and parasites are less of an issue in a greenhouse, since neighborhood deer or a swarm of locusts can’t get to the protected plants.

When plants are safely inside, frost, windy conditions, pesky rabbits (and everything in between) no longer pose threats. It’s almost like cheating—except when you’re winning, who cares?

Greenhouse Success: The Basic Requirements

A greenhouse is a climate control box for your plants. You can get as simple or as fancy as you’d like, depending on how much you’re willing to spend. This guide will focus on the bare bones method of taking it from foundation to a permanent structure, and then explore some of the many available greenhouse styles.

A greenhouse should have:

  • Proper location
  • Ventilation
  • Air circulation
  • Watering system
  • Temperature control


The location of your greenhouse determines your plants’ success. Do your best to position the greenhouse where it will receive morning sun during the summer and winter months. Afternoon sunlight can be intense on its own, but in a greenhouse the light may be magnified by the glass and in turn burn plants. The ideal effective shading includes deciduous trees to the west to provide dappled shade in the intense summer months, and winter sunlight when the trees drop their leaves. If the ideal shading is unavailable, use an opaque roofing material to help disperse sunlight.


Ventilation provides gas exchange. Plants inhale the carbon dioxide we exhale, and exhale the oxygen we inhale, so provide openings in the house to facilitate these exchanges. Natural ventilation is easy to accomplish with side vents and roof openings at the highest point in the structure. This takes advantage of convection currents, where heated air rises through the top and pulls cool air in through the sides. (This is the same mechanism that explains wind currents on Earth.)

Shoot the Breeze: How to Ventilate Your Greenhouse


Air circulation keeps the gases moving throughout your climate box. Proper circulation helps maintain a consistent temperature throughout the greenhouse; otherwise cool air sits at the bottom near the plants and warm air is trapped at the top of the structure. The best way to mix it up is to install small fans at opposite ends of your greenhouse to create an oval pattern of air circulation.


Plant watering depends on the habits of the overseer. Hand watering crops works well if you are available on demand. However, it only takes a warm weekend of slacking off to put plants under water-stressed conditions. Automatic watering systems, on the other hand, are a plant saver. Whatever plants’ needs are, there is a watering system to meet those requirements.

There are two basic types of watering systems that control the frequency of your watering schedule. One is an automatic timer that turns the water on at a pre-programmed time and duration. The other system is controlled by evaporation sensors that determine when greenhouse conditions are too dry. Water emitters come in all shapes and sizes, from misters to drip, soakers and fog. Whatever conditions plants require, there are watering systems available to emulate everything from an equatorial rainforest or a red rock desert.

Temperature control

All plants have temperature requirements, and if conditions become too warm or cool, they will suffer. A Los Angeles greenhouse in February has much different requirements than the same greenhouse in Denver. Depending on the climate and the parameters of a greenhouse, a heating or cooling system may be beneficial. Your local garden experts can provide more info on this.


Building an affordable greenhouse is pretty doable when it comes to upcycling materials. Cleaning out the garage, dumpster diving the neighborhood, scouring the free section on Craigslist, or visiting the local re-store will reveal the materials available right under our noses.

Prepare the foundation

You will need:

  • Flat head shovel, rake
  • Pressure-treated boards for base frame
  • Landscape fabric
  • Landscape staples
  • Heavy duty staples
  • Pea gravel

Step 1: Determine the location. Create a flat, level surface for your greenhouse. Remove rocks, plants, barbed wire, and other debris from the area. A flathead shovel and rake is typically sufficient.

Step 2: Install a four-inch ABS pipe that allows you to run water or electrical lines from the exterior, underground into the greenhouse. The black ABS used for sewer lines is cheaper than white PVC. Temporarily seal the ends of the pipe to prevent soil from entering. (Duct tape works well for this.)

Step 3: Build a frame at the perimeter of the greenhouse area to hold gravel for drainage. Frame material should be made of something rot-resistant, such as pressure-treated wood.

Step 4: Line the area with polypropylene landscape fabric to suppress weeds. Staple the edges to the frame so the silt fencing does not slip and weeds do not grow in between the frame and the base material. Landscape staples can be used to hold the fabric in place. Fill this area with two to three inches of pea gravel for drainage.

You now have a naturally draining foundation!

Building Your Greenhouse Base: The Foundation

The house

Your greenhouse design can be as creative or utilitarian as you choose.

The upcycled window greenhouse is a permanent structure that puts old windows and doors to good use. The basic idea is to build a sturdy frame and attach windows. Remember to account for the fan, side vents, and roof vent in your design to accommodate ventilation and air circulation. Also, check with your local building codes, which vary from town to town.

Greenhouse Dreams: Peppers in December

Hoop houses are a quick and easy way to protect your plants from the elements. They can take the form of a low-laying tunnel or a large walk-in structure. The hoop house has the benefit of being semi-portable and easy to set up from readily available materials. But using a hoop house means the plastic material has a shorter life span, temperatures are difficult to maintain, and there’s no support for snow. Hoop houses are handy for early-season frost protection as they warm the soil sooner to provide a head start on crop production. (Check out the Natural Resource Conservation Service’s building plan for a simple ground level hoop house design here.)

Greenhouse Dreams: Peppers in December

Funky yet functional

Feel like thinking outside the box? People have built greenhouses out of 2-liter plastic bottles and geodesic domes, and even created structures heated by chicken coops. There are no structural boundaries to what you can grow your plants in as long as you rely on five principles: location, ventilation, air circulation, irrigation, and temperature control.

Out of the Box Greenhouse

Whichever greenhouse ends up in your yard, it’s hard to regret checking this item off your “someday-maybe” to-do list. Knowing plants are protected from the elements while you are away is worth the time and effort put toward your DIY greenhouse. Impress your friends with freshly harvested arugula and spinach salads during the holidays. Go ahead and make the neighbors jealous of your red peppers in December. Remove the barriers from weather-confined gardening to year-round greenhouse growing.

Planning on building a greenhouse after reading this article? Consider getting one of these garden benches to set your plants on or for you to sit on and enjoy nature. —

Greenhouse Dreams: Peppers in December

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Danielle Castle

Danielle Castle

Danielle started as a field biologist in 2005. She has worked with conservation research projects involving the Caspian tern, northern spotted owl, and red-crested cardinal in North and South America. She served as a biological consultant conducting botanical inventory, nesting bird surveys, rare species surveys, and habitat restoration. Danielle earned a Bachelor of Science in Ecology and Systematic Biology, and a Master of City and Regional Planning with an emphasis on environmental planning from California Polytechnic State University, San Luis Obispo. Writing about curiosities provides her with the intellectual intrigue similar to that of poking at stuff with a stick. Whatever the topic, if you give it a little nudge, you never know what surprises it may reveal.
Danielle Castle

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