If you live in a climate that has less-than-ideal growing conditions for much of the year due to frost or cold weather, there are many things you can do to extend the growing season by weeks, months, or even indefinitely – even in the coldest climates.
1. Choose the right plants
First and foremost, choose plants that will yield in the amount of time you have. Most annual vegetables can be grown in most places if started early (see below), but if you choose a perennial that doesn’t belong in your zone, it may not produce anything even if it does survive the winters. Learn everything you can about a plant’s needs for soil, sun, water, daylight hours, temperatures and humidity, and choose the ones most adapted for your climate (but don’t be afraid to experiment, too).
2. Use green houses
Probably the most well-known way to extend the growing season is to use green houses. The best designs for energy efficiency and resilience are passive solar green houses. They are sometimes built into south-facing slopes, and usually have windows concentrated on the south, and sometimes the east, and west sides, while the north side is generally heavily insulated or made of thermal mass such as stone or earth.
There are many designs online to explore, from in-ground walapinis, to bermed designs, to aquaculture focused, to simple free-standing versions. Add a rocket mass heating stove or other stove to your green house, and you will ensure a year-round growing season with little risk of freezing. You might even consider attaching the green house to your home so you can exchange heat between the two buildings.
3. Use cold frames
The little sister of green houses, cold frames can be an invaluable way to extend your season using salvaged materials such as old patio doors and scrap wood. Just as with green houses, you can build them into slopes or berms, but it also can be as simple as throwing a frame on a window and placing it over a bed at a height suitable to your plants. You also can create temporary quick and dirty cold frames quickly by piling logs or other materials around your beds and placing windows on top of them. Make sure you have a way to ventilate the cold frame, whether through incorporating hinges and a way to prop the windows up, or through removable sides. As with a green house, you also can attach cold frames to your home to either exchange heat, or to simply benefit from a south-facing wall.
4. Use microclimates
Microclimates are simply areas within your garden that have different temperature or humidity qualities than the rest of your garden. South-facing walls are an example, as mentioned above, as are southern hills, large rocks, pond or lake edges, or well-sheltered areas (e.g. from buildings, trees or hedges). These will all make conditions more favorable for growing less hardy plants. Likewise, avoid the frost pockets caused by obstacles or land forms (e.g. low-lying areas) that may cause frost to collect.
5. Stagger plantings
Continue planting appropriate crops throughout the entire season, including right into the fall when you can plant cold season crops like spinach, chard, kale, or beets. Once you harvest a crop, plant another crop right away, considering how much time you have before first frost. Of course, you also can plan for putting a cold frame over a crop or use other methods below if you expect it won’t be ready in time.
6. Plant diversity, including perennials
Branch out beyond the common annual vegetables, many of which have less tolerance to cold than some other annuals like globe artichoke, or radicchio, and especially perennials. Perennial vegetables like sea kale, good King Henry, garden sorrel, and many others are often poking out of the ground weeks before you plant your first annual out. And why stick to vegetables and herbs when you also can benefit from the abundance and ease of maintenance that trees, shrubs, and vines can bring? Try fruit like strawberries, juneberries/Saskatoon berries, raspberries, kiwi, and haskaps, as well as nuts like hazelnuts, pecans, almonds and cherries to keep the harvest coming all season.
7. Incorporate mounds and raised beds
Raised beds and soil mounds will warm up earlier in the spring, and stay warmer later into the fall. Although they may have some drawbacks, such as drying out faster and requiring more work to create, incorporating at least a few raised beds or hills/mounds can extend your season at least a little. Make sure to mulch a little heavier to compensate for the increased moisture loss.
8. Build rich soil
The more organic matter and nutrients that are in your soil, the faster your plants will grow, which means they are more likely to yield faster and better before the first frost. Rich, lofty soil also can act like insulation for your plants’ roots, while ongoing breakdown of organic matter may even create a little extra heat.
9. Mulch heavily
Mulching your soil with at least 4-6 inches of mulch will insulate your soil and plant roots, moderating soil temperature extremes. Temporarily putting even more mulch (even more than a foot deep) around less hardy plants for the winter may even allow you to plant things that normally wouldn’t survive the winter in some places. If deep mulching temporarily, make sure to remove the mulch back to around 6 inches in the spring to ensure the plant can make its way to the surface.
10. Start seedlings and plant early
Many vegetables are best planted a month or earlier before last frost indoors, including tomatoes, eggplants and peppers. Some plants don’t transplant well, such as most squashes, but everything else is game for starting seedlings early to ensure they get a good start and produce earlier. Get to know your region’s expected frost dates, watch the weather carefully, and plant as early as you can. Consider growing extra plants and planting some of them earlier when there may even still be danger of frost, and then if frost does strike, either protect the plants, or replace frost-damaged plants with your extras.
11. Protect plants
Collect old blankets, sheets, plastic, tarps or any other similar coverings you can, and when frost is expected, be prepared to drape them over your more sensitive plants. To avoid damage to your plants from the weight of the material, put stakes in the ground around your plants that reach beyond the top of the plants, and lay the coverings over them for the night, securing them with stones, sticks, tent pegs or similar. This simple technique alone could add weeks to your growing season.
Whether you want to extend your gardening season by a few weeks, or keep the food and medicine coming all year with a green house, these methods are a good place to start.