Good to Grow: Extend your growing season with cold frames and more

Have you ever noticed in the movies something magical always happens in the greenhouse? The couple finally kiss, the writer finds inspiration, the pouting children are found, or the detective solves the case; no wonder, greenhouse or conservatories are the perfect backdrop for just about anything!

To me these scenes are dream sequences — I can’t imagine access to such places. These elaborate spaces have the Hollywood touch, but owning your very own greenhouse is not just for the movies anymore.

The one in your backyard may not be up to the standards for Captain Von Trapp and Maria, but there are several options for the home gardener as a way to extend the gardening season.

The most basic is a cold frame. This is a simple structure very much like it sounds, a frame with a hinged or removable top built to protect plants and extend the growing cycle. Cold frames typically do not have an independent heating source and are built low to the ground.

To take advantage of the winter sun, be sure to build so that the frame is south facing. Using a cold frame will keep fall crops growing and allow you to plant early in the spring. For airflow, the hard top can be raised or removed for short amounts of time.

This is a way to begin lettuce, radishes, and other spring crops before planting in the open garden. The cold frame can also be used for plants that are dormant in the winter. Keep in mind, without a heat source, the plants in a cold frame are protected from the weather but will freeze if the temperatures are low.

I remember the first time I visited a friend who had a greenhouse. I thought she was so fancy. That was not something ordinary folks like me had at home. These days, you can buy them for under $100. Oh, at that price they will be small, but give you enough space to overwinter a few houseplants, maybe even grow a tomato plant or start seeds in the early spring.

The small, portable greenhouses are heavy plastic stretched on a frame. They will sit on top of an outdoor plant that is still in the ground, or keep a few potted plants growing through the winter.

As the building size grows, so does the price, but there are fabulous options. The stand-alone greenhouse is taller and has a door; it can be made of plastic sheeting or glass. One of my favorites is made from collected windows. It is gorgeous and has a potting bench with underneath storage bins below built along the wall. Talk about a gardener’s dream.

No wonder my friend has the earliest greens and vegetables. She starts her seeds early, think tomato, peppers, even favorite annuals such as zinnias, and nasturtium, giving her healthy plants that are garden ready when the outside soil has warmed.

Another popular way to build a greenhouse is to lean-to another structure, often the back of your house. These lean-tos use the building structure for support and as the fourth wall. The size is limited to the wall and how much support is given to the rest of the lean-to. These are popular because they are easy and very accessible; you just walk out the back door.

Regardless of the material or size of your greenhouse, there are a few must-haves. You need sunshine, at least 6 hours of sun. This will provide the main heat for the plants. In colder climates, or if growing tropical plants, you may need to have a heater installed.

The sun will heat the air and just as you learned in science class, hot air rises, so your greenhouse will need ventilation — a vent at the top to allow the warmer lighter air to escape and a vent near the bottom for cooler air to enter. This air movement will be good for the plants. You may want to open the door or have a removable window for milder days.

Having access to water is also important. Depending on how you are using your growing space (tables with trays or hanging baskets), you may be able to use drip irrigation or maybe you enjoy the getaway and will use a watering can to give each plant a drink. Either way, having water nearby makes it much easier to control the moisture of the soil.

Think about any commercial greenhouse you have visited, they are always warm inside. Growers can regulate the temperature inside to create the microclimate needed for what they want to grow. Interested in orchids or other tropical plants? You can adjust your greenhouse. Another bonus, pesticides are rarely needed in a greenhouse and crops are protected from wildlife.

Although a movie set conservatory is out of reach for most of us, with a little planning and a little luck, we can find a way to extend our love of gardening through the winter months.