Monday, September 17, 2012

Ideas for extending the garden season

Now that cooler fall temperatures have arrived (even after almost 30 years in St. Louis, the rapidity of the September cool-down continues to amaze me), you may be wondering how to keep your garden going as late in fall as you can. Mid September is too late to start seeds for full-sized crops of fall cabbage or lettuce, though you could sow a small patch thickly to lettuce and other greens and get some salads this fall as you gradually thin out the patch. However, there are a few crops you can start from seeds now and get a good-sized plant. You may be able to find seedlings on sale at some garden centers that you can plant now to grow on for the next month or two. Here are a variety of ways to extend the garden season into late fall or winter along with my assessment of how they fit with the Living Low lifeway. Next post will discuss living-low food storage, so you can stock up from your garden or nearby farmers markets and eat well during the cold months.

Experimenting with what you have now
If you’ve ever wondered how long your favorite garden lettuce could survive into the winter, the easiest way to find out is to leave a few plants in the garden past the time you would normally harvest them. Ditto for anything else you grow. Just because I, or the Missouri Extension, or anyone else says that tomatoes don’t survive a frost, or lettuce won’t overwinter in St. Louis unless it’s under cover, doesn’t mean that’s what will happen in your garden. Your garden may be in a spot which cools down faster or slower than the rest of your yard or the average for the area (what gardeners refer to as a microclimate), so your tomatoes might frost out even if the rest of your yard didn’t show any evidence of frost. Or you might be growing a hardier lettuce that can stand colder temperatures before it freezes out compared to what I’m growing or what the Extension uses as a standard. The only thing you lose by leaving a plant in the ground is the food value of the plant if it dies before you can harvest it.

It makes sense to consult with the information that the Extension, for instance, puts out on frost tolerance of vegetables and fruits and planting dates for fall crops, and to consider if your garden is located in a microclimate that could alter expectations, when you are considering what kinds of experiments you might want to do. I’ve noticed that my vegetable garden frosts before anywhere else in the yard because it is the most open area and thus experiences the most radiational cooling on still, clear, cold nights. If your garden is a little shaded or just south of your house or garage, your garden might not frost even if the rest of your yard does. Most any garden book or information source can tell you how to recognize and use microclimates to your advantage in extending the season. I do experiments of this sort, sometimes intentionally, sometimes because I get caught with too many veggies to harvest before a freeze so things I had intended to harvest get left in the ground. The Living Low Way embraces the effects of chance as well as the results of good planning.

Grow the most cold-tolerant vegetables
An easy way to extend the season is to look for vegetables that can stand a lot of cold weather, especially the combination of wide temperatures swings, freeze-thaw cycles, and lack of sustained snow cover that makes it difficult to overwinter most vegetables in St. Louis and the lower Midwest in general. These might be specially bred varieties of particular crops, such as ‘Ice Bred’ arugula compared to other varieties of arugula. Or they might be types of vegetables that are much more cold tolerant or able to withstand freeze-thaw cycles than are others. I use this strategy a lot. Below are some cold-tolerant vegetables that have done well for me, but please don’t consider this an exhaustive list.

Root crops: radishes, turnips, beets, carrots, parsnips, and leeks all thrive during the cool weather of fall and into early winter, and taste the sweetest after the first frost or three. You can wait to dig these out until just before the ground freezes. I’ve accidentally left carrots in the ground all winter, during one of the rare winters when the ground was frozen for the entire winter, and most of them survived to be dug up and enjoyed once the ground finally thawed out in early March. I don’t know if they would do as well in our more usual freeze-thaw cycles. Parsnips are supposed to overwinter successfully in our area although I haven’t tried them yet. The information I’ve read suggests that beets, radishes, and turnips won’t overwinter here, but I hadn’t confirmed that experimentally. I don’t know about leeks. So far I’ve harvested all of these before the ground freezes solid. My favorite fall radishes are the large (4 to 6 inches across) storage radish varieties such as ‘Red Meat’ and ‘Black Spanish Round’, although the salad radishes are also very cold-tolerant. Except for the radishes, you won’t get full-sized crops from planting seeds of any of these in mid September, and you needed to plant leeks last spring for harvest in the fall.

Tatsoi, an Asian salad green in the cabbage family, has a pleasing appearance, with dark green spoon-shaped leaves arranged in a low rosette, and a mild mustardy-cabbagey flavor. It can take an amazing amount of cold, standing until the worst of winter, long past when most lettuce freezes out. This is one crop you could sow now and expect to get a decent harvest. Some other Asian greens may also grow quickly enough to be sown now for a decent crop. Look for varieties with under 60 days to maturity (30-45 days is best for planting this late).

Arugula also takes a lot of cold in my garden, with the ‘Ice Bred’ variety from Fedco supposedly taking more cold than most arugula, though I haven’t done a side by side comparison yet. This is another crop you can sow now and get a decent amount of food for your trouble.

‘Bronze Arrow’ lettuce seems to take more cold than other varieties of lettuce I have grown, but you can grow any lettuce if you harvest it before lows get into the mid 20sF. Sow your seeds thickly, then thin the patch a few times starting early in October and eat the thinnings in your salads. If you are lucky, you might find lettuce seedlings for sale now. I started seeds of the lettuces in the photo at the beginning of this post in early August and planted the seedlings on September 10. I expect they will grow to a good size before it gets too cold for growth to continue.

Kale is another very cold-tolerant green; in fact, it seems to taste best in the colder days of late fall and early winter. This might overwinter as a small plant if you sow it now. Or you could buy ornamental kale and plant it for looks, then harvest and eat it before lows drop below 10-15F. The ornamental kales might be best as cooked greens, but try them both raw and cooked to find out.

The champion of cold-tolerant salad crops is mache. You don’t sow it till around the end of September or early October, yet it still grows and produces a full-sized crop in late winter and early spring! The catch is, a full-sized plant is very tiny, just a few inches high and across. You’d need a huge amount of it to give you much food. It grows as a winter groundcover in my asparagus patch along with some winter weeds. Even though we get little food from it, it takes care of itself (I allow some plants to flower and go to seed in spring so it comes back on its own) and by itself or as an addition to a purchased salad it earns its keep when it is the only edible green available in February or early March. It has a mild flavor unlike that of any other salad plant I’ve tasted.

Use mulch for extra protection
Mulch can be used in a thick layer to keep the ground under it from freezing and hence allow you to dig a root crop through winter. I have mulched sunchokes thickly, using the abundant autumn leaves shed by the oaks and maples in the yards around us that blow into our yard. A foot-deep layer of leaves will keep the ground underneath from freezing, allowing me to dig out sunchokes in January. However, by early spring there are no sunchokes big enough to bother with left, and the roots I do find are obviously chewed on. I think that voles or other small vegetarian mammals feast on the roots all winter long in their cozy, unfrozen bed. By contrast, some carrots that I left unmulched in ground that froze were still alive and uneaten in March when the soil thawed out, although some of the carrots in the patch had succumbed to rot. If you have free or cheap mulching materials available, try mulching some root crops you’d like to hold into winter and see what happens.

Potato onions (perennial onions that develop from single bulbs into a clump of bulbs as do shallots) and garlic need to have a few inches of mulch over them to carry them over the winter in a climate with winter freeze-thaw cycles such as we experience. Left unmulched, they will heave out of the ground during mid-winter thaws. I’ve tried pushing them back into the mud, but most frost-heaved bulbs die despite my attempts at saving them. However, I have also had mulched bulbs die because I failed to remove the mulch in early March when the plants resume active growth, so manage mulch correctly if you choose to use it. Last winter, we never got a long-lasting freeze. I hadn’t mulched the bed with the garlic and potato onions, but since we didn’t get much if any freeze-thaw cycling, almost all the garlic and most of the potato onions survived the winter and grew well over spring.

Use row covers to protect against light frosts and freezes
A row cover is a piece of fabric or plastic that you place temporarily over some plants to protect them from low temperatures a few degrees lower than the threshold to kill the plants. They are most often used on a cold, still, clear night when good radiational cooling will allow a light frost or freeze to occur. The fabric or plastic mimics a light cloud cover, keeping enough heat from radiating out to raise the temperature underneath it the few degrees needed to keep whatever is underneath the cover alive. Usually after the first light frost or freeze there will be several days to a few weeks before it gets so cold that a row cover won’t save the plants from cold weather, so you can keep a tomato or pepper plant alive long enough to ripen the nearly-ripe fruits, or keep your lettuce bed alive for awhile past the time the low drops into the mid 20sF for the first time. Because row covers can be as simple and low-cost as a few old sheets or blankets that you prop up with whatever is handy to be slightly taller than the crop you are protecting, this strategy fits very well into the Living Low Way. You can also purchase specially-made garden fabrics to confer specified degrees of cold protection if you have the desire and money to do so. In my case, I figure that if it’s so cold that my collection of multi-purpose old sheets won’t keep a plant alive, it’s time to either harvest it or bid it goodbye for the year.

Use a cold frame to protect cold-tolerant crops
A cold frame is a bottomless box, made to fit over part of a row or garden bed. It’s generally a foot or two tall. The box top is one or more pieces of glass or plastic to allow sunlight to enter. Think of a cold frame as a tiny greenhouse, something that anyone with a few pieces of wood and a scavenged storm window or piece of plastic can put together. Its ability to be cobbled together from scrounged parts fits into the Living Low lifeway, as does the fact that it relies only on the sun for sufficient warmth to shelter some plants into the winter and even the following spring.

Mike constructed two cold frames, about 10 feet long and three feet wide, from a mix of new and reused wood and reused storm windows that we placed in permanent spots due to their weight and large size. Here are pictures of the cold frames and a crop inside one of them, taken in late fall 2003.

I made a garden bed in the ground inside the larger frame and grew a selection of salad and greens crops in it for a few years, till the frame rotted out. I wasn’t as happy with the cold frame as I had anticipated. Its size wasn’t large enough to grow much food and the crops didn’t seem to grow as much as I expected; this may have been poor management on my part or poor construction of the frame. The windows needed to be propped open on sunny days and closed again once the sun went down, something that would be difficult or impossible to do for anyone not home during the day. Hailstones broke a couple of the glass panes in the windows on my frame. My experiences soured me on the utility of cold frames for growing food crops. (I have a cold frame much like the smaller one now because it is very useful for raising seedlings, something I’ll discuss in posts on starting seeds.) But a cold frame might be perfect for you, especially if you already have the parts lying around and you’re of a mind to try it out to see how it works. If I were making another frame, I’d either make it small enough that I could carry it by myself to a garden bed and plop it onto the portion I wanted to protect, or I’d make a cold frame that could be put together on the spot in fall and taken apart and stored in pieces in spring. I might also use a piece of polycarbonate plastic rather than glass to cover the frame so the occasional hailstorm didn’t poke holes in the clear top.

Use low hoop structures to protect a garden crop
Low hoop structures, sometimes called quick hoops or low tunnels, are a variation on the cold frame theme. A low hoop structure is a large piece of plastic draped over a series of low metal hoops arranged along the length of the row or bed you wish to protect from winter cold. Low hoops might be 2 to 3 feet high in the center of the protected area, with the metal hoops spaced a few feet apart. They seem to be used most often to cover garden beds about 30 inches wide but could be sized wider if you garden in wider beds. Low hoops are becoming quite popular on vegetable farms as a way to protect late fall and early spring crops. The major advantage of a low tunnel over a cold frame is that a low tunnel can cover a much larger area since it is built in place over an existing row or bed from lightweight parts. One person can build the tunnel; the hoops can be reused for many years and the plastic can be reused for a few years if nothing like stray hailstones, animal claws, or other sharp objects puncture it, you weigh it down well enough to keep winds from carrying it off, and you take care to avoid tearing it when putting it on or removing it. (In St. Louis excessive weight from snow cover should not be an issue since we rarely get more than 6 to 8 inches of snow in a single storm, usually much less. Ice storms, on the other hand, could create excessive load, and we do get them on occasion.) To me the major disadvantages of a low tunnel are its use of plastic film, something that will go up in price and become less easily available as the oil from which the plastic is made depletes, and their appearance. I cannot see beauty in a low tunnel the way I can in a well-constructed cold frame (not that our cold frames were beautiful, quite the contrary). Low tunnels share with cold frames the disadvantage of needing to be vented on sunny days and closed before the sun goes down. I wouldn’t blame anyone for wanting to put up a low tunnel or three, however. It’s the most cost-effective way to protect a large area of overwintering greens and root crops. Johnny’s is a good place to start your search for supplies to build a low tunnel.

Use a high tunnel to protect crops
High tunnels are low tunnels that are tall enough to walk into. You may have seen these at a garden center where they grow their own seedlings for sale or at a local vegetable farm, where they are used to grow crops or seedlings when it’s too cold outside to grow them. You can buy these in kit form in various sizes, or buy the components and make your own. Compared to low tunnels these are larger so they hold more food, and they are easier to work in since you are able to stand up inside them instead of needing to reach in from the outside. They will also swing less in temperature than a cold frame or low tunnel due to the larger volume underneath the covering in proportion to the surface area of the covering, although they will still need to be vented on sunny days. The disadvantages are the same as for low tunnels, plus they cost a lot more and require a lot more plastic. A large enough one might need a permit to be constructed.

Use a greenhouse
Whenever we are out and about I look for greenhouses. There is something about them that appeals to me, even the cheap or dilapidated ones. I associate them with sunshine and warmth, green plants and the sight and fragrance of flowers in the middle of winter. Apparently the greenhouse marketers have done their work well on me. The reality of greenhouses falls far short of my vision, I’m afraid. Freestanding greenhouses of traditional construction may look good, especially the more well constructed (and hence expensive) ones, but if you are expecting a tropical paradise in the middle of a St. Louis winter, you’ll be disappointed. They have too much exposed glass to retain overnight most of whatever solar heat gain they received during the day and hence will drop below freezing most nights for a few to several weeks in midwinter. You could heat them, but that is already an expensive proposition and likely to become more so over time. You’ll need to vent them on sunny days so they don’t overheat and close the vents before the sun goes down. They will be too hot for you and plants from May through September and perhaps some of April and October as well, even with the vents wide open. All this is due mostly to the glass roof and the north-facing glass wall. The roof allows too much sunlight in during warm and hot weather and the roof and north wall allow too much heat to escape in cold weather. On top of that, they are expensive to construct and vulnerable to hail (unless you get the polycarbonate versions). If you want a traditional greenhouse that is actually useful, you’d best move someplace with more cloudy days all year and warmer winters than we have.

Solar greenhouses supposedly minimize some of the disadvantages of the traditional greenhouse by using a solid, insulated north wall and a partial solid, insulated roof along with heat absorbers such as 55 gallon drums filled with water. For more information, you should read The Solar Greenhouse Book, edited by James C. McCullagh. This 1970s classic is long out of print. You may be able to borrow it from your local library or request it through interlibrary loan, or you might be able to purchase a used copy as I did. Of the various versions of the solar greenhouse it describes, the one I think is most useful here is the attached greenhouse with vertical glass walls and a solid, insulated roof. We have a name for that: an enclosed porch.

Use an enclosed porch
If you already have or can build onto a house or outbuilding an enclosed porch with partial or full glass walls, or you can cover screened windows on such a porch with plastic for the winter, and especially if the longest wall faces more or less south, you have the version of a solar greenhouse that I think works the best in St. Louis’ climate. The roof provides needed shade during summer while allowing the lower winter sun to shine into the porch. The vertical glass walls are less vulnerable to hailstrikes than slanted walls and let through most of the low-angled winter sun while reflecting away some of the higher-angled summer sun. The solid north wall and solid roof help keep some of the heat in during cold months, especially if either or both is insulated. Whatever building it’s attached to also shields from wind on that side. Hence an attached porch used as a greenhouse will generally stay somewhat warmer in winter and somewhat cooler in summer than does a traditional greenhouse. You can increase winter heat storage on a porch the same way as described for a solar greenhouse. If you already have an enclosed porch with partial or full glass walls that is oriented more or less south, you’ve probably already noticed that it can be pleasantly warm on a sunny winter day. All you need to do is grow some vegetable plants in containers from late fall through early spring and you can have the occasional fresh veggie treat. Unless you are fortunate enough to have a huge porch you won’t be able to eat a salad every day, but if you enjoy growing food and can tend your plants over winter, you might find it worthwhile. Unless you want to grow something like tomatoes that can’t take any frost, you probably won’t need to add heat to such a porch in the St. Louis area.

Our house had an open porch (a roof and a concrete floor but no walls) on the south side facing the street. Because we aren’t confident builders and the porch was visible from the street, we decided to hire professionals to enclose our porch. You can see it in the photo below.

We enclosed the porch two years ago, primarily to provide a warm-enough space to keep my potted citrus trees and tender perennial herbs over the winter and to allow some of the heat captured by the porch to enter our house. It does the first well and the second some, better in late fall and early spring when there are more hours of daylight available. (It would do better at heat gain overall if the huge pin oaks next door and across the street weren’t shading it too much in the early afternoon.) Over the next couple of weeks I’m going to pot up the excess seedlings of lettuce and salad greens left over after I planted the fall garden. I’ll put the pots on the front porch when freezes begin, in late October or November. In this way I’ll learn whether or not I can grow enough salad greens on the porch to be worthwhile. Expect a report next year!

If your porch is on an east or west facing wall rather than a south facing wall, it won’t heat up as much but it may still be useful for season extension. Our previous house had a screened porch attached to the east-facing wall, so it had a north, east, and south wall with screened windows. By covering the windows with greenhouse plastic in the winter, I could keep my citrus trees on the porch most of the winter. I raised seedlings on it in the spring. I probably could have kept containers of salad vegetables on it during winter if I’d thought to try it, though it did get colder in midwinter than our current south-facing porch has. If your porch is attached to a north facing wall, however, it’s probably too cold and dark for season extension. But you don’t need to take my word for it: try keeping a 6 inch pot of lettuce on it this fall and winter and see what happens. It might work (though I suspect it would freeze out by January).

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