It’s the end of October, which means that for many garden zones the first freeze is imminent. For many gardeners, this signals the end of gardening for the year. However, there are a myriad of ways to prepare your garden for the oncoming cold and extend the fall growing season well into winter. In today’s post, well cover how to protect your plants from a surprise frost and structures you can utilize to grow productive vegetable beds in freezing temperatures.
One of the easiest ways to protect your garden from a single evening frost is to simply cover vulnerable plants in the early evening before temperatures reach freezing. For smaller plants, this can be as simple as placing overturned pots/buckets over the plant or covering them in mulch. For larger shrubs/trees, covering the plant in cloth such as old bed sheets will provide enough insulation to minimize the damage. For best results, use poles to keep the cloth off of the foliage.
Photo by Manfred Werner, Blumengärten Hirschstetten in Vienna, Austria
In commercial operations, many nursery operators and produce farmers utilize sprayer irrigation to protect large amounts of plants from freezing at once. This practice seems counter-intuitive at first, but the energy released from water freezing into ice can prevent the plant temperature from dipping below the freezing point of water in certain circumstances. This requires constant mist irrigation throughout the freeze event and may not be economical for your average gardener. However, watering the soil around the plant before a freeze can protect the roots through the same thermodynamic mechanism. The ground/root area of the plant should be watered deeply a day before the freeze is forecast, when the temperature is above 40 degrees Fahrenheit, and should be done early in the morning as to allow the plant time to absorb it during the warmer temperatures of the day.
Now that we know how to prep our garden to survive a freeze event, let’s turn our sights on how to have your garden thrive during the fall/winter seasons. Greenhouses represent the epitome of environment controlled gardening and are by far the most effective way to keep your plants healthy during the cold season, but these structures are cost-prohibitive to most hobby gardeners. However, there are some cheaper, easily constructed options that work on the same principles and can be tailored to your needs. These include: Hoop houses, low tunnels, and cold frames.
Hoops houses consist of PVC, conduit, or other material poles curved to form a semi-circle placed in parallel with one another with clear plastic stretched over top to create a covered, insulated area for growing plants. More advanced hoop-houses utilize heating and venting systems to keep plants at an ideal growing temperature. Hoop houses generally cover a large area and are big enough to be worked from inside the structure. Low tunnels draw on this same design but rarely involve any mechanical control elements and are sized to fit individual raised garden beds.
Photo by the USDA, Hoop Houses at the White House Garden
Even without the temperature control elements, hoop houses/low tunnels help insulate plants from freezing temperatures by collecting heat and humidity during the day from the plant’s respiration. Clear plastic (polyethylene is commonly used) at-least 6 millimeters in thickness provides enough insulation while also letting enough light in to maintain plant growth and health. Occasionally these structures, like all covered growing structures, need to be vented in order to provide air for plant respiration.
Another structure you can utilize for winter gardening is the cold frame. Cold frames essentially consist of a box with a hinged window on top that seals in the air and lets light in, creating a micro-climate. Cold frames are generally used to harden-off seedlings that have been grown in a controlled environment, and allow the seedlings to adjust to outside conditions without the overwhelming stress of being planted directly outside. If effectively managed, all three of these structures can be planted with fall season vegetables, be harvested well into mid-winter and be used to jump start the spring growing season.