Time to Plant
It is August in Colorado and time to prepare for planting. At my altitude, 7,400 feet in the foothills of the Rocky Mountains, the growing season is short -- last frost early June, first frost any time after Labor Day. In order to achieve the goal of fresh vegetables ten months of the year, I have learned to extend the growing season through the hot summer and into the freezing winter.
I have one gardening rule of thumb: work with nature in the simplest, most cost-effective way possible. This approach excludes expensive solutions that require high inputs of electricity or heating. When the power goes out in February and there is three feet of snow on the ground, I need to know that my plants will brace themselves and survive without much help. I also have to find ways to save seedlings planted in August from cooking in the hot dry soil, or crisping from sunburn.
Late summer, rather than spring is the beginning of my growing year. If I start at this time, I do not have to endure those empty months without fresh home-grown vegetables. There is one twist however, the techniques for fall and winter gardening are kind of backwards from what most gardeners are used to.
In early spring we protect seeds and seedlings from cold until the sun and soil warms up. As the days gets hotter, we take care that the soil and plants do not over-heat. In late summer the problems are exactly the opposite. We first need to protect seeds and seedlings from over-heating until the sun and soil cools down. As the days get shorter, our goal is to guard the soil and plants from killing cold.
In pursuit of continuous nutritious vegetables, I rely on three simple protective coverings: floating row covers, transparent polyethylene film and knitted shade cloth.
The most basic and useful protection in the garden is floating row covers. Row covers are multipurpose: they moderate temperature, reduce moisture loss, protect from frost and provide shade. When I plant seeds, I cover the soil with the fabric and water through it. This stops the seeds being disturbed and cools the soil through evaporation in summer. Whenever my plants look stressed, whether from cold, heat or bugs, I reach for the row covers.
If row covers are multi-use, transparent films and shade cloth are used for specific objectives – to adjust light and heat. Transparent coverings are best thought of as solar collectors, harvesting the sun’s energy and maximizing its benefit through the “greenhouse effect.” The clear skin allows the sun’s rays or photons to pass through; these are captured through partial reflection from the undersurface. Under a transparent covering, the soil warms up; heat is stored in the ground and released slowly during cooler times. Whenever there is a shortage of energy for your plants, whether in the form of light or heat, use a transparent solar collector.
Garden catalogs are filled with different transparent or translucent films. These generally fall into two categories: rigid sheeting such as glass, polycarbonate or acrylic, and flexible films such as polyethylene. Although polycarbonate sheeting has superior insulation and durability, I prefer 6 mil poly film due to its ease of handling, low cost and adaptability. With it, I can create any size and shape of protective structure, from large greenhouses to small individual plant covers.
In the cold season we need to collect solar energy, but in the heat of summer that energy needs regulating. That is the role of shade cloth. Of the two main kinds of shade cloth, woven or knitted, I prefer the durable knitted form and use the 40% variety. This decreases sunlight by 40%, and can reduce the temperature at plant level by 10°F. When direct planting cold weather crops in July or August, I double up the fabric to help the seeds germinate. Whenever you need to decrease or moderate the sun’s energy, set up the shade cloth.
Floating row covers do just as the name implies -- float on top of your plants as they grow. The covers need no extra support; simply peg them to the ground with garden staples so they do not blow away. In contrast, transparent film and shade cloth require support structures. What shape or size of structure depends on the limitations of your space, imagination and budget. Everything from an oversize greenhouse to a small wire frame is simply a structure to hold up protective coverings. With so many options, always build or buy the structure that best reflects your long-term needs.
I have been experimenting with low cost structures for many years. This summer, I completed my third greenhouse from metal conduit and poly film. Even with this protected space available, I still use the simple tunnels I designed seven years ago. These are triangular frames, 10” to 15” high, made of ½” white PVC tubing covered with poly film or shade cloth. The triangular shape sheds snow well and needs only a few six inch wire garden staples to hold the tunnel down, even in 70 mph winds. See box.
To protect seeds or transplants in late summer, I loosely place the floating row cover over the seeds and water well. The triangular frame, roofed with shade cloth, is placed over the row cover and pinned down on one side with the garden staples. This allows the tunnel to be hinged open to examine seedlings.
As soon as there is a chance of frost, the shade cloth is replaced with poly film. I allow 12” extra poly on each end. This can be folded and clipped to the frame when I close the ends of the tunnel as the weather gets colder. The combination of row cover and poly solar collector is usually enough to protect my crops through the winter. When things get really cold (10°F and below), I use row covers and tunnels inside the unheated greenhouses to provide extra protection for more vulnerable plants.
Choosing Cold Weather Vegetables
When choosing which vegetables to grow, the first question you need to ask is: what can survive my kind of winter? Only then can you pick the types of vegetables you prefer. For us Northern gardeners, visions of tomatoes, corn and beans are excluded unless we are willing to add heat and light. That leaves us with varieties that can survive the cold, often by going dormant in the depths of winter. There are plenty to choose from.
Cold hardy vegetables that do well in early spring are just what you need for late summer planting. Choose varieties that are labeled cold resistant and fast maturing. Crops take longer to grow when days are short, so add 14 days to your expected harvest date and pick leafy plants when they are small and sweet. Most cool weather seeds germinate in moderate soil temperatures between 60F and 75F. Some such as spinach and lettuce are shut down by heat, so keep those seeds cooler.
As a beginner winter gardener, I suggest you start with some of the fail-safe varieties of greens: spinach, chard, turnip tops, beet greens, chinese cabbage, bok choy, collards, broccoli rab, and kale. If you want to be a little more adventurous, try the salads: winter lettuce, mache, endive, chicory, radicchio, arugula, cress, and mizuma. With a little more planning and earlier seeding, you can have root vegetables: carrots, bunching onions, garlic, parsnips and beets.
I often plant packets of mixed seeds, especially those for spinach, mesclun or winter lettuce. These usually include some hardier varieties that will crop well. Seeds are inexpensive so keep trying different varieties to see what works best for you.
Many gardeners simply accept that September is the end of the growing season. They put their garden to bed and wait through the long winter for the first signs of spring. What they are missing is the excitement of harvesting baby salad in November, the satisfaction of providing family and friends with nutrient rich greens in February. With a little planning and some simple equipment, fall becomes the start of your growing season.
High-Yield Gardening: How to Get More from Your Garden Space and More from Your Gardening Season. Marjorie B. Hunt and Brenda Bortz.
Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long. Eliot Coleman and Barbara Damrosch.
Solar Gardening: Growing Vegetables Year-Round the American Intensive Way. Leandre Poisson and Gretchen Vogel Poisson.