One way to improve resiliency as well as quality of life is to grow your own vegetables locally. However, gardeners in northern climates are especially challenged by limited growing seasons. In this brief article I will show examples of how to easily extend and preserve the harvest and have fun doing it.
Why Extend Your Harvest?
Presently we can drive to the supermarket to get nearly anything we want even in winter. The fresh fruits and vegetables we see have often been grown thousands of miles away in a tropical climate and flown in using a lot of energy may not be so cheap or plentiful in the future. As well as potentially reducing dependence on energy, extending the harvest of your own foods has advantages including:
- Less work and simpler than preserving by canning or freezing
- Fresher, higher quality than canned
- Less expensive than supermarket
- Increased resiliency with the option to of a local food source
- Controlling your own food sources is more pleasurable and rewarding
All these pluses for extending your own harvest can add up a higher quality of life. You may not meet your major calorie needs (that is probably better done with stored grains and potatoes), but you’ll have a source near your doorstep of fresher, vitamin-rich greens to round out your meals.
In the summer of 2008, I was already putting attention back into a neglected backyard garden from earlier years, when I stumbled on to the concept of Peak Oil and the need to adjust my lifestyle. Unfortunately, the initial garden was a complete disaster, mostly resulting in raised beds of massive weeds. Clearly I still had a lot to learn , but nearing the end of August in New England left me little time to salvage the season. Fortunately, I found Eliot Coleman’s book Four-Season Harvest. I used ideas from this book, plus Square Foot Gardening methods for organization, to get much improved results before the end of that year.
How to Extend the Harvest
Some principals of extending the harvest include:
- Adapt to your climate
- Plant vegetables successively
- Choose hardy crops for cold weather
- Protect your crops with simple devices like cold frames.
Adapting to Your Climate
The idea is to not fight your climate during the cold seasons with expensive heated greenhouses and growing lights. Instead, get to know your local climate! For example, when is your first frost date in the fall? At my house, the first hard frost came on October 11 in 2009 and on October 18 in 2010. Then use the other principals above to adapt to the climate you have.
Planting vegetables at intervals from spring to summer to fall extends the harvest of fresh vegetables as much as possible. As your vegetables mature, they can be harvested as you need them. This avoids the need for larger time investments to preserve large batches of food that mature all at once. As the fall approaches, you will transition to hardier crops and crop protection.
Choosing Crops for Cold Weather
Coleman’s book has lots of great information on which vegetables do well in cold weather and when to plant them. My favorites that I have been able to carry right into December in cold frames include:
- Scallions/green onions
- Claytonia (miner’s lettuce)
- Mache/corn salad
Other common veggies that not only tolerate but can thrive in cooler seasons include:
- Carrots (especially the Napoli type)
Some of the hardiest cold weather greens that I had never heard of before reading Coleman’s book include Claytonia, Mache, and Tatsoi. They are also much tastier than iceberg lettuce from the supermarket and richer in vitamins.
Plant seeds for the veggies you like to eat and skip the rest. Other sun-loving vegetables like tomatoes and corn are best enjoyed in season and preserved for the rest of the year.
Managing the Extended Harvest
Coleman states in his book that this innovative thinking involves realizing that only the harvest season and not the growing season needs to be extended. The idea is to grow vegetables during the warmer seasons, hibernate them during colder, dormant seasons, and harvest as needed.
Carrots grown in the heat of summer, for example, just don’t seem to taste good if not promptly harvested when matured. But I’m amazed at how long they last in the fall when kept stored in the garden bed. The trick is knowing your climate and getting the timing right. In 2009, I found that carrots planted the end of August did not mature in time before winter, but this year I was on the ball and had a large crop from seeds sowed August 1. The carrots were kept in raised beds under cold frames right up until the risk of the ground freezing was imminent. Then I pulled most of them in late October and stored them in the root cellar. Those carrots are still fresher tasting than the ones from the supermarket, which only seem to last a week or two at most in the refrigerator.
Greens like spinach, chard, and lettuce are not really for storage, but can handle a few freezes, especially if protected in a cold frame. The best way to harvest is to take a few leaves at a time as you need them. While the water is coming to a boil on the stove for pasta or potatoes, I go out at night with a headlamp and snip what I need for the evening with scissors.
While the hardy winter greens can usually tolerate freezing while they are still rooted, they will not be very palatable if harvested while freezing. Except for mache, tatsoi, and scallions, wait until the temperature rises above freezing before harvesting.
The photos below show some lettuce (Winter Density) that I harvested on January 1 this year after shoveling snow off the cold frame. Temperatures the previous week had dipped to 15F at night outside, but a warm day allowed me to get a fresh salad 20 feet from my kitchen.
I’ve noticed some overwintered plants do much better than seeds planted in early spring. For example, spinach planted in the fall in my cold frames will carry on until about December, then re-appear with vigor again around March as the days grow longer again. Those same plants will produce leaves until hot weather in June when they bolt and go to seed. Then it’s soon time again to plant more and repeat the cycle. You can also get a jump start in spring by planting some spring crops in the cold frames as soon space opens up from harvesting fall and winter crops.
Cold Frame Construction
Cold frames are a simple, low-cost alternative to greenhouses that let light in, help contain heat from the earth below, and protect vegetables from harsh conditions of cold temperatures, wind, rain, and snow. Basically, a cold frame is a box with a hinged transparent top known as a "light." There are a number of options to use to construct cold-frame lights, including old windows, sliding glass door panels, plastic sheeting, acrylic sheets, and corrugated polycarbonate panels. They can work well in conjunction with raised beds. Be cautious, though, about the potential dangers of broken glass.
I’m always on the lookout for old windows and glass doors by the curb on trash pickup day, and have accumulated a collection out back. Below is a photo of a 3’ by 6’ raised bed covered with a double-pane patio door that my neighbor was throwing away. After he saw what I did with it, he wished he had kept it!
The best location for your cold frames is close to the house and facing south. The handier they are to your kitchen, the more likely you are to go out to harvest something, rather than just reaching into the refrigerator. I have some frames right in front of my house next to the driveway in a sunny spot, and interested passer-bys often stop to ask what is growing in there!
The sides of the cold frame are made from 2” thick spruce planks screwed together with deck screws and the light is secured with some old hinges. A slope of about 1” vertical to every 12” horizontal seems to be about right.
I’ve also made low tunnels or hoop houses with ½” PVC pipe and polyethylene plastic sheeting. This allowed me to size the tunnels to match existing cold frames that were too big for patio doors or windows. Disadvantages are that the plastic sheeting is not as durable or as insulating as glass and wood.
Prefabricated cold frames can also be purchased, but they are generally beyond my budget. Check some out, though, if you need some design ideas.
Cold Frame Management
The two most important things to control in managing your cold frames are temperature and water. On sunny days, the temperature in a cold frame can become like a sauna. You will need to be sure to provide enough venting during spring and fall when the sun is higher. I keep sticks of various sizes handy to prop open the cold frame lights as necessary. In winter, no venting may be necessary at all. If in doubt, erring on the cool side is better than the risk of cooking your veggies.
Much less water is needed during the cooler months since there is less evaporation. Once in a while I’ll add a little water gently on a sunny day so the leaves can dry off before evening. In winter there is no need to water at all.
A short list of resources is provided I have found helpful and that will link you to more sources of information if needed. Also search online for “cold frames” and you’ll find many more ideas for construction.
- Eliot Coleman’s book The Four Season Harvest has is a wealth of information. Also check out his website for other resources.
- Johnny’s Selected Seeds company sells seeds for the hardy cold weather vegetables.
- Mel Bartholomew’s All New Square Foot Gardening has some great ideas for organizing your vegetables in raised beds