This is the tenth in a twelve part series for new gardeners. If you have never planted vegetables before but always wanted to, this is the series for you. Robin, who writes the blog Vegetable Matter, and I will post on the first of every month. Robin lives in Houston and I live in Boston. We will be posting about what to do in the garden that month and giving advice. So if you have always wanted that vegetable garden, but didn’t know where to start, you have no excuse. Get growing!
Our growing season in Massachusetts is not very long. Our cool weather crops start at the end of March or early April by planting peas and spinach and end after a good freeze sometime in November. We have about seven months. Our warm weather crops have even a shorter life span. Maybe four months. We can plant usually sometime in late May and then our first frost shows up in October. But many of us want fresh vegetables for a longer period of time. We want fresh vegetables all year long.
Location, Location, Location
One easy way of making your season a bit longer is site selection. Most home owners don't have much of an option of where to put the garden, but if you have multiple sites to chose pick a south facing slope. South facing slopes heat up much faster in the spring and can thaw out weeks before a north facing slope. Don't put your garden in a valley. Put it near the top of a hill where the cold air can flow down the slope. Valleys collect cold air and can have much shorter growing seasons. I used to live near the top of a hill and the bottom of the hill often got frosts in the fall a week before we did.
But that is just extending the kind of growing you already do. If you want to actually harvest a lot earlier, for example when we have snow on the ground, the best place for the garden is right out your back door. The closer you are, the more often you will visit the winter garden. If you have to shovel snow way to the top of a hill to get to it, it just won't happen as often as you might think it will. The edge of your house foundation is often warmer than any other place in your yard regardless of the lay of the land. The concrete is a good heat sink and your house leaks heat too. Just be careful about planting there if you don't know the house's history. Usually in the northeast the foundations have termite barriers surrounding them. These are strong pesticides that tend not to break down over time and some have been banned due to their toxicity.
Harvesting in the winter really isn't that hard if you pick the right crop. Certain crops overwinter well even in the north without protection. Kale and mache are probably the easiest. Kale stands upright and can be picked through the snow. It is best to get the plant to a good size before winter starts. You might want to stake it as the heavy snows can knock it down. Mache is a very short plant and can be picked during thaws.
Another plant that overwinters well (in Eastern Massachusetts) without any protection is spinach. You can't really pick it during the winter as the overwintered leaves get very ratty, but in the spring when it starts to grow again, it will be a very early harvest. Overwintered spinach can often be a better producer than spring planted spinach.
Many root crops can be heavily mulched to keep the soil from freezing. Carrots, parsnips, turnips, beets, bunching onions, and potatoes all fit into this category. They may not keep all the way through winter, but at least through December. Just pile the bed up with leaves or straw about a foot or two thick before the first freeze. If you see any sign of freeze in the bed, immediately pull up all the rest of the crops.
One step up from mulching with straw is a floating row cover. These are often used in the summer to protect the plants from insect damage, but heavier weight ones will also protect from frost and hold heat in the bed. A simple floating row cover will not keep in enough heat to grow things over the winter, but it will extend your season on either end. Spinach overwinters particularly well under a row cover.
Floating row covers can either be put right on top of the plants (with a little give so they can grow). Or they can be put over hoops. Hoops can be made from different material. I've used 9 gauge wire. If you put the wire in as a simple hoop one after the other like below:
the wire is not strong enough to stand up to snow. But if you cross two of them and use a twist tie in the middle to hold them together the structure becomes much more sturdy. Some people use PVC pipe to hold up row covers. PVC is much sturdier than 9 gauge wire.
Hoops made from PVC, photo copyrighted, courtesy of Laura from The Modern Victory Garden
Others use electrical conduit wire that can be bent. And still others use wooden structures.
Tunnels made from bent conduit in the snow, photo copyrighted, courtesy of Thomas at A Growing Tradition
It is often useful for PVC or conduit hoops to have a ridge line to keep the hoops from bending under the weight of the snow. But in the end what you need is something sturdy that won't collapse under a couple of feet of snow.
Row covers can either be floating row covers that are made of lightweight porous material or they can be made of plastic. Plastic will hold in the heat and heat up better during the day. This is both an advantage and a disadvantage. If the day gets to be 60F (15C) outside, your poor plants can bake and die. You have to be very vigilant about venting the ends or rolling up the sides on warm days. In addition you have to water. A floating row cover is porous and water will come in when it rains, but not if you use plastic.
If you truly want to harvest all winter long you need both. The outer cover of plastic and an inner floating row cover. This protects the plants pretty well. They can still freeze, but inside you would only plant things that are very hardy. Onions, carrots, brassicas, and lettuce are all good candidates. Pick varieties that are the hardiest ones. The plants won't actually grow much during the winter. It is really too cold, but they will hold in the ground and grow during the warmer spells.
In addition to plastic above the plants, warm weather vegetables can be started earlier by having plastic mulch under the plants. To further protect warm weather plants you can add milk jugs or soda bottles filled with water. The more you put in the better protection you will have.
For the typical home gardener the cold frame is the Cadillac of winter protection. They have wooden walls and a glass top, often slanted to catch the sun better. Sometimes they are insulated on the inside. They are a lot like the plastic row covers, but they can retain heat they absorb from the sun. Plastic really has no insulating value so once the sun sets the plants get cold. If the cold frame is well built, this doesn't happen. In addition you can get an automatic thermostatically controlled opener for the lid so you plants won't fry on hot days when you forget to vent the cold frame.
Cold Frame, photo copyrighted and courtesy of Dan from Urban Veggie Garden Blog. Follow the link to see instructions on how to build it.
Though cold frames typically aren't heated, people sometimes use manure to heat the frame (often called a hot bed). They dig fresh manure and straw deep in under the plants 24"-6" under the soil, with 6' of good soil on top. The heat that comes up from its decomposition helps keep the cold frame from freezing. This used to be a very common practice a century ago, but now that farm animals aren't as prevalent it is harder to find fresh manure.
Hoop Houses and Greenhouses
Most home gardeners don't have hoop houses or greenhouses. Hoop houses are the cheap man's version of the green house. They are made with metal pipe hoops and often have wooden frames for doors on the ends. They are easy to get as kits in different sizes. They are covered with plastic, which as we have discussed before, is not very insulating, but many hoop houses have a double row of plastic which has an insulating air layer between. Typically these are not heated, but sometimes are heated with compost. Composting puts out a lot of heat and can be used to keep a hoop house warm. In addition there is often a heat sink of some kind. The most common that I've seen are black barrels filled with water. Even the ground can be a heat sink if it is black enough and kept very moist.
Greenhouses are very expensive and made of glass. Small ones can be bought as kits, or there are plenty of companies that will build one for you. I've even seen one made out of old random windows patched together. Everyone wishes they had one (including me), but they aren't all that common because of their expense. Even most commercial farm operations around here go for hoop houses to raise their seedlings in. But they are invaluable if you want to grow tender crops all year long. Most people here just live without those wonderful tomatoes until tomato season hits. But if we have prepared well in the winter we eat greens from the garden and dream of warmer days to come.
Other Posts in the Series
Determining your growing zone and planting peas (Vegetable Matter - December)
Planning a Garden (Daphne's Dandelions - December)
Growing Lettuce (Vegetable Matter - January)
Starting transplants indoors (Daphne's Dandelions - January)
Growing tomatoes (Vegetable Matter - February)
Compost (Daphne's Dandelions - February)
Snap Beans (Vegetable Matter - March)
Peas and Spinach (Daphne's Dandelions - March)
Eggplant (Vegetable Matter - April)
Brassicas (Broccoli, Cabbage, Asian vegetables) (Daphne's Dandelions - April)
Edamame (Vegetable Matter - May)
Tomatoes (Daphne's Dandelions - May)
Lima Beans (Vegetable Matter - June)
Disease Control (Daphne's Dandelions - June)
Chili Peppers (Vegetable Matter - July)
Insect Control (Daphne's Dandelions- July)
Southern Fall Garden (Vegetable Matter - August)
Preserving the Harvest (Daphne's Dandelions - August)