For beginning farmers and homesteaders, season extension is one of the most valuable ways to improve yields, increase income, and provide fresh food for longer periods of the year. One of the simplest and most cost-effective tools for this is a cold frame—a low-tech structure that traps heat and protects plants from frost.

Whether you’re looking to start seeds earlier in spring, grow greens through the winter, or protect tender plants in the fall, a cold frame is an easy solution that doesn’t require expensive equipment or heating costs. Even better, you can build one with materials you may already have on hand.

What Is a Cold Frame?

A cold frame is a simple, unheated greenhouse that uses solar energy and insulation to create a warmer microclimate for plants. Traditionally, it’s a bottomless box with a transparent lid that allows sunlight in while trapping heat and shielding plants from wind and frost.

A well-built cold frame can:
✅ Extend the growing season by several weeks in spring and fall
✅ Allow you to start seeds earlier for transplants
✅ Provide a protected space for overwintering hardy greens
✅ Reduce the need for artificial heating or expensive season extension tools

Cold frames work especially well for Indiana farmers in USDA Hardiness Zones 5b to 6b, where spring and fall frosts can shorten the growing window.

Low-Cost Cold Frame Designs

Building a cold frame doesn’t have to be expensive. With repurposed materials and simple tools, you can create an effective structure for little to no cost.

1. Repurposed Window Cold Frame

One of the easiest ways to build a cold frame is to use an old window or glass door as the top cover.

Materials Needed:

• A repurposed window or storm door
• Scrap wood, bricks, cinder blocks, or straw bales for the frame
• Hinges (optional) to open and close the window for ventilation

How to Build:

1. Create a rectangular base using wood, bricks, or straw bales. The back should be slightly higher than the front to create a slope, allowing water runoff and better sun exposure.
2. Place the window or door on top to act as a transparent lid.
3. If using wood, hinge the window for easy opening to regulate temperature.
4. Position the cold frame in a sunny, south-facing location for maximum heat.

✅ Cost Estimate: $0 - $25 if using salvaged materials

2. Plastic Tote Cold Frame

For a quick, portable option, large clear plastic storage totes work well as mini cold frames for individual plants or seedlings.

Materials Needed:

• Clear plastic storage tote with a lid
• Drill for ventilation holes (optional)

How to Use:

1. Place seedlings or small plants inside the tote.
2. Snap the lid shut on cold nights, then open it during the day for airflow.
3. Drill small ventilation holes to prevent overheating.

✅ Cost Estimate: $5 - $20 per tote

3. PVC Hoop Cold Frame

For a more flexible, tunnel-style structure, a PVC hoop cold frame is a great option for covering multiple garden rows.

Materials Needed:

• PVC pipes or metal hoops
• Clear plastic sheeting or greenhouse film
• Wood or bricks to secure the base
• Clamps or stakes to hold the plastic in place

How to Build:

1. Insert PVC pipes into the ground to form arching hoops over your garden bed.
2. Drape clear plastic sheeting over the hoops and secure the edges with bricks, wood, or stakes.
3. Lift or open the plastic on warm days to prevent overheating.

✅ Cost Estimate: $20 - $50, depending on materials

4. Straw Bale Cold Frame

If you have access to straw or hay bales, they make excellent insulated cold frames that hold in heat and protect plants from wind.

Materials Needed:

• 4 to 6 straw bales (make sure they are unsprayed)
• Clear plastic or an old window for the top

How to Build:

1. Arrange straw bales in a rectangular shape, leaving the center open for planting.
2. Place a clear plastic sheet or an old window on top.
3. As temperatures rise, lift the cover slightly to provide ventilation.

✅ Cost Estimate: $10 - $30 (if purchasing straw bales)

Tips for Using a Cold Frame Successfully

1. Ventilation is key. Even in winter, a sunny day can quickly overheat a closed cold frame. Open the lid or prop it slightly on warm afternoons.
2. Monitor moisture levels. Cold frames reduce evaporation, so water as needed to prevent dryness.
3. Choose the right crops. Hardy greens like spinach, kale, lettuce, and chard thrive in cold frames, as well as herbs like parsley and cilantro.
4. Position for maximum sun exposure. A south-facing spot with wind protection is ideal.
5. Insulate in extreme cold. On frigid nights, throw an extra blanket or straw over the frame to retain heat.

Why Cold Frames Are Perfect for Beginning Farmers

For new farmers looking to maximize their growing potential without expensive infrastructure, cold frames offer:

• A low-cost way to extend the season without heated greenhouses
• Protection for delicate crops against unexpected frosts
• An easy method for starting seedlings for spring planting
• A scalable solution—start with one frame and expand as needed

Whether you’re growing food for your family, selling at a farmers’ market, or experimenting with season extension, cold frames provide an affordable, effective way to improve production.

Cold frames are a simple yet powerful tool for Indiana farmers looking to extend their growing season without significant costs. Whether you build one from scrap materials, repurpose a plastic tote, or create a larger PVC hoop structure, the benefits of frost protection, early seed starting, and season extension are well worth the effort.

By incorporating cold frames into your farm or homestead, you can grow more food, reduce losses from late frosts, and enjoy fresh greens even in the colder months.

Would You Like Hands-On Guidance?

If you're interested in learning more about low-cost season extension techniques, Veterans IN Farming offers workshops and resources to help you make the most of your growing space. Stay tuned for upcoming events and classes!