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Low Tunnel

Low Tunnel

Season extension structures resembling low tunnels are a great way to protect overwintering vegetables. I use them to have fresh greens—kale, collards, and chard—on the table through the winter months. They are easy to build with plastic pipe and either clear plastic sheeting or greenhouse plastic. I would love to not have any plastic in my garden, but until I have a better alternative, I make an exception for this.

Plastic pipe easily bends to form the arches that hold up the plastic cover. My garden beds are 4’ wide and I use an 8’ length of plastic pipe (1/2” inside diameter) for each arch, giving me a tunnel with a height of about 30”. Some people use metal electrical conduit for their arches, bending them around a homemade jig. I space the arches about 4’ apart down the length of the bed. Another piece of plastic pipe is put on top, becoming a ridge pole to connect the arches. A screw is used to attach the ridge pole to the top of each arch. It is important to have the ridge pole.

My arches are held in place by either putting them over pieces of rebar extending up from the ground or by inserting them into larger pieces of plastic pipe, also extending up from the ground. Whether rebar or larger plastic pipe is used, the pieces of each are cut to 2’ lengths. Plastic pipe can be cut easy enough and you can buy rebar already cut into 2’ lengths. Look for rebar where cement blocks are sold. One foot of each anchor piece is driven into the ground, leaving 12” sticking up to receive the end of the arch.

Next comes the plastic cover. You can find clear plastic sheeting in a hardware store or big box building supply store (look for it in the paint department). Make sure it is 6 ml thick to withstand the winter weather. This construction plastic has no UV protection, but since you are only using it through the cold months, you can get a couple years use out of it if you store it out of the sun and keep the mice away during the off-season. Greenhouse plastic is good if you can get it since it will last longer. If you are building a structure that will be in the weather all year long, go with greenhouse plastic. A piece 10’ wide is good to go over the 8’ arches covering my 4’ wide beds.

The easiest way to secure the plastic cover to the pipes is with plastic clips, called garden clips or snap clamps, that are sold for this purpose. Johnny’s sells them and they are available at other garden and greenhouse supply sources. You can make some from plastic pipe, but if you need to take them on and off, the ones you buy are easier to work with. Okay, I know it is December already and if you had greens to protect, most likely you have already put up a structure like this if you intended to. I’m really writing this post to talk about the covers. You can build a low tunnel from these directions, but if you stop here you will have problems when the wind picks up or when it comes to harvesting from your tunnel through the winter.

Screw eye inserted into arch secures row cover cord.

Screw eye inserted into arch secures row cover cord.

The plastic covers on my low tunnels stick out 12” on the sides. Some gardeners put sand bags, rocks, or pieces of wood on that extra to hold the cover down. On a calm day, it might seem to do the job, but the wind will easily whip the plastic out from under these things. Besides, if you have 18” wide paths like I do, there is no extra room for sandbags, rocks, or pieces of wood. You will be tripping over these long after the covers were removed in the spring, unless you are diligent in taking them up. It would take putting many clips across each arch to secure your plastic cover enough to hold it through high winds. Even if you were willing to work with that many clips, you need to be able to access the plants inside through the season and it isn’t practical to be messing with so many fasteners each time.

My solution is to put a cord across from one arch to the next, alternating sides. You need the ridge pole to hold the cord up. I usually use 1/8” nylon cord found in hardware/building supply stores, but have used old clothesline if that was available. If you already have a low tunnel and have experienced problems with wind, you can add this feature and alleviate problems the rest of the winter. It involves putting a screw eye near the base of each pipe the cord attaches to. I use a drill to make a pilot hole for the screw eye.

The bungee provides tension to hold the cord securely to the cover.

The bungee provides tension to hold the cord securely to the cover.

Years ago when I first did this I thought I needed to build a wood box and use pipe clamps to hold the arches, screwing the screw eye into the wood beside the pipe. Later I discovered that it is fine putting the screw eye directly into the plastic pipe. Of course, there is more material to screw into if there are two layers of pipe (the anchor pipe and the arch pipe), but it also works well if the arch is put over rebar. I have not put a screw eye into a metal pipe, but I imagine it would work well, also. If anyone has done that, I welcome your comments. Using a bungee cord between the screw eye on one end arch and the cord helps to apply tension to the cord.

The cord holds the plastic sheeting in place for venting or harvesting.

The cord holds the plastic sheeting in place for venting or harvesting.

There are so many great things about securing the cover this way. Most importantly, it doesn’t come off in the wind. Another advantage is that all those things you put in the path to hold the plastic down are not necessary anymore. And the harvest—it is so easy! You can lift the plastic at any point along the sides to harvest and it is held in place under the cord. You will still use clips, but only on the end arches. The cover can be cut to come a few inches over the end arches and be secured with the clips. A separate piece of plastic sheeting can be cut to fit the ends. In mild weather it can be left off. When it is needed, it can be secured with the same clip that holds the tunnel plastic, holding two pieces at once. There are so many ventilation advantages with a separate end piece. Once the weather gets severe enough for me to put on the end pieces, I will fold the top edge down for ventilation on the warmer winter days.

Venting the row cover ends.

Venting the row cover ends.

I got the idea for using a cord over the plastic cover from Eliot Coleman in his book Four Season Harvest. He used wire arches with a loop bent into it to anchor the cord. Arches from plastic or metal pipe with a ridge pole can withstand more severe weather than the wire arches he described. If you have been having trouble with the plastic covers on your row tunnels and haven’t used a cord to secure them, take the time on a mild day to go out to your garden and make the upgrade. You will be happy you did.Homeplace Earth

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coldframe 4 lids onI have known for the past two weeks that the subject of my blog would be coldframes—I don’t always know what I’ll write about that far ahead. However, I thought the title would be Coldframe Transplants. Before I began writing the new post I reviewed my previous posts about coldframes and realized that I had written much of what I would say this time in Use Your Coldframe All Year last May. So, I encourage you to read that post. I had taken some good photos of my coldframe in April and realized that I could focus this post on coldframe lids.

The coldframe in the photo is 4’x 8’ and has four 2’x4’ lids made from twinwall polycarbonate panels. They were made from one 4’x 8’ twinwall panel that friends gave me when they were replacing the glazing on their solarium. I have considered putting wood frames around the twin wall panels to protect the edges, but haven’t gotten around to it. With a coldframe this big, using one panel for a lid would be awkward to use and to store. My previous coldframe was 3’x 6’ because I was given a piece of glass that size that I framed in wood. One advantage of that lid was that it was heavy enough not to blow off in the wind when I had it lifted on one side for venting. A disadvantage of that lid was the weight and size when I stored it in the barn for the summer.

coldframe-4 lids openI have never liked using hinges on coldframe lids because hinges would limit their use. I want to be able to move the lids around or take them off completely. When I taught at the community college one of the projects I assigned was to plan a season extension structure for a 4’x 25’ bed—complete with a drawing of the design, list of materials, and how it would be used. If the students chose to use a series of coldframes I always warned them I would take off points if there were hinges on the coldframe lids. Sometimes you need to take them all the way off. If you tilt them back, as in this photo, there needs to be room for them behind the coldframe.

coldframe vented at the topThese panels are relatively light. If I had them lifted on one side to vent, the wind may blow them off. It can get pretty windy in the spring. I was gone for five days the second week of April. Things were just coming up in there, so I wanted to keep the lids on while I was gone. However, looking ahead to the weather, it looked like some days would be quite warm. I decided to turn the panels parallel to the long sides of the coldframe and lower them a bit, leaving a vent space at the top. That would keep everything warm enough, but not too hot. It was nice that the day before we left for the trip we had an inch of rain—with the panels off.

coldframe lids stacked - BLOGSometimes I stack the panels on the coldframe if I want to vent it a little more than I did when I went on the trip recently, but still keep some protection there. If I was going to vent that way more than a day or two, I would not stack the panels, but take two away so as not to prevent light transmission. The extra panels can lean against the side or back of the coldframe, ready to put back on when needed. When I store the panels for the summer they only take the footprint of one panel.

Your coldframe lids might be old windows or wooden frames covered with plastic. Consider all the different ways you might use them before building your coldframe, so as not to limit your possibilities.  By this time of the year, you may be frost free and can store your lids for the summer, but your coldframe will still be of service as a space to grow transplants all through the growing season.Homeplace Earth

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melting snow 2-18-14A recent snowfall gave me an opportunity to take some new photos. Things can come and go right before our eyes, and if we don’t take the time to look carefully we’ll never see them. I like to take photos of the snow melting to remind me of the variations in soil temperature and the micro-climates we have everywhere. I mentioned soil temperature in my post on Phenology. This garden photo was taken on February 18. The weather was warming and the first place the snow began to melt was on the south side of my garden beds, which run from east to west. When I see this in late winter I’m reminded of the idea I’ve always had in the back of my head to make the soil on a garden bed slant towards the south. This could be done in the fall and the bed would be ready early in the spring, or even late winter, for planting. The soil would warm first on the whole bed. With a cold frame on top, things could get off to a really good start.

melting snow in coldframeSo far, however, my coldframes have stayed on flat ground. The covers slant, since the front (south) side is 8” tall and the back (north) side is 12” tall. On February 20 I took this photo of the coldframe which had no cover for the winter because it wasn’t planted. The snow had melted everywhere except the places with the most shade. Since the sun is so low in the sky during these winter months, it casts a longer shadow. If I would have had a cover on that coldframe, the snow would surely have melted everywhere in there. However, the front of the box would still be shading the strip of soil beside it. The sides of the box cast a shadow, also, but only for part of the day. The east side (foreground) is shaded in the morning and the west side is shaded in the afternoon. The strip to the south (with snow) stays shaded all day until spring when the sun is sufficiently high enough in the sky to peek over the edge all day.

You could solve that problem by using a clear plastic row cover. With clear plastic coming all the way to the ground you don’t have that shaded area on the inside; however, the structure itself will shade just to the north. You can see that by the row cover in the topmost part of the coldframe photo. The area to the north of the coldframe is also left with a bit of snow where it is shaded. I don’t have plans to plant anything directly to the north of these two structures, but it is interesting to note. When I plant seeds in the coldframe I plant many rows. I run these rows across the short way, north-to-south. If that bit of shade on the inside is enough to affect anything, it won’t affect all of one thing.

melting snow by board fenceOther interesting snow / shade spots are to the north of our board fence. You would think that since there is space between the boards, the sun would reach through. There is also a line of snow to the north of the hazelnut hedge in the upper left of that fence photo. There is a wire fence there and the hazelnut trees have lost their leaves, but it is still enough to leave a snow line.

You don’t have to have snow to notice the shaded areas, but it is a whole lot easier. When I took the first photos on February 18 the snow had melted in the front yard, but not in the back yard (north side of the house). On February 20 when I was out with the camera I noticed that half the snow had melted in the backyard. There was still snow in the area that showed up as a shadow on the snow in my photos two days earlier. Last summer I paid particular attention to the sun and shade there in the flower bed near the house (very last place for the snow to melt). I was looking for a space to plant a few cotton plants that I wanted to keep separate from my other cotton. I determined that the sun was high enough, and would be that way long enough, for the cotton. It was with careful consideration that I put those cotton plants there. That would have worked, too, except that the summer was extremely cloudy and even the cotton that was planted in the sunniest part of the garden didn’t mature. Oh well.

I’m sure you’ve noticed the days getting longer and spring will be here before you know it. The sun will cross the sky a little higher each day, making the shadows not quite so long. If you pay attention to the little nuances occurring in your garden you will be off to a good beginning as you start your seeds and set out transplants.Homeplace Earth

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after the frost foodThe first hard frost of fall has come. I think it happened here on October 24. I can’t say for sure because I was in Ohio visiting family. I knew the seasons would be changing in the eight days I would be gone. In preparation for leaving I was busy cleaning up the garden, which goes hand in hand with building compost piles, and planting cover crops. When I returned on October 30 the leaves on the trees had changed colors and the newly planted cover crop seeds had sprouted.

When the first hard frost comes in the fall, everything changes in the garden. The pepper plants that were so lush the day before are now wilted, along with so many other warm weather crops. That doesn’t mean your garden is finished for the season, however. This is the time for the cold weather crops to take center stage. I look forward to the frost bringing out the sweetness in the carrots and greens. In fact, I don’t worry about growing carrots to harvest in the summer anymore because we are so spoiled with the ones we have in the cold months. For the next six months we will have sweet carrots fresh from the garden. I’ve previously written about how I grow my winter carrots.

Other fall and winter crops that we eat fresh from the garden are beets, Jerusalem artichokes, collards, kale, chard, and parsley.  There are more root crops that I could add to the list, if I had grown them this year. Those crops are turnips, Daikon radish, and kohlrabi. No doubt, some of my readers could add more choices. With onions and garlic, potatoes, sweet potatoes, cowpeas, and peanuts from stored harvests, there is a wealth of food one can eat without further preservation. Our winters here in Zone 7 are not so mild that we don’t need protection for the greens if we want to have a continual harvest. Even at that, picking once a week is what to expect, and less frequently during the weeks of the least daylight, so more area needs to be planted for winter harvest than needed for a spring planting.

kale-row cover-carrots-BLOGI don’t cover the carrots and beets with anything so as not to encourage voles to move in. They are planted early enough to be mature now, so only need to be held in cold storage in the soil. For protection from harsh winter weather for the greens I use low tunnels made from plastic pipe and old greenhouse plastic. This type of cover is easy to erect. The ½” plastic pipe can be inserted into larger size plastic pipe stuck in the ground or put over pieces of rebar. The rebar and larger plastic pipe is cut to 2’ lengths and put half in and half out of the ground. If you leave rebar in the ground without a hoop over it, be sure to cover it with a plastic bottle, piece of plastic pipe, or an old tennis ball. You don’t want anyone to get hurt if they stumble upon it. You can find rebar precut to various lengths in the building supply stores near the cement blocks. Plastic pipe comes in 10’ lengths. I cut it to 8’ to form a hoop over a 4’ wide bed. These pipe structures also have a pipe across the top and a cord (anchored to the bottom of the hoops) that goes over the plastic cover to keep it in place. More details about that are at my blog post Managing a Cold Frame, Low Tunnel, or Mini-greenhouse. The plastic is held to the end hoops with clips made especially for that purpose. They are nice to have.

row cover clip

row cover clip

Having this bounty of food available in my garden all winter is the result of careful planning done sometimes a year in advance. To have the cabbage family greens at a good size now is sometimes a challenge, since they would have been started during hot weather. I have to keep a vigilant watch to pick off cabbage worms and harlequin bugs during those weeks. The seeds are started in the coldframe, not because they need protection, but because the coldframes are my seed starting areas. I do, however, sometimes cover the coldframe with a shadecloth if the weather is too hot and sunny. Once established, the best plants are transplanted to the garden beds. The winter covers don’t go on until cold weather hits. I’m just now bringing the covers out. A big advantage of using this type of low cover, rather than a greenhouse, is that the covers are easily added, removed, or vented, allowing the plants to get the full benefit of the natural climate, including the rain.

If you don’t have this variety of food available in your garden after the frost, and would like to, start making notes now and work on your garden plan to make it happen next year. Go ahead and prepare a bed and put a cover on it now, or at least put up the hoops and be ready for a cover. In late winter you can use it to get off to an early start. Put the cover on two weeks before your planting time to warm the soil. When my community college students planned a season extension structure for their projects, many of them constructed their designs, but put in transplants and seeds too late for a fall or winter harvest. However, often they found they had a very early spring harvest from those plants, especially with things like spinach. If you have the time and inclination to prepare now, it will put you one step ahead for early planting next spring.Homeplace Earth

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coldframe filled with seedlings

coldframe filled with seedlings

Coldframes are great solar powered seed starters that you can use year round. If you’ve built one, used it in the spring, then left it to become overgrown with weeds for the rest of the year, now is the time to rethink that. This can be your go-to place for transplants all season, plus a place to harvest winter salads while waiting for the next round of seeds.

I generally start planting in my coldframe in early February with cabbage, collards, kale, chard, and other cool season things. If I am starting onion seeds, I might plant them in the coldframe in January. My next round of planting is for the warm weather crops, such as tomatoes and peppers. These are started about the last week in March, however this year it was April 5 when that happened. This year was a good year to not be in a hurry, since the weather was unseasonably cold and damp for longer than expected.

When I started seeds under lights in the house, I used to start tomatoes and peppers on March 1. They would require a lot of attention and watering. When it was getting close to time to plant them outside, I would have to harden off the plants—get them used to the outdoors—before they actually got planted in the garden. I’ve seen people having to do this with greenhouse plants. They would lug them in and out of the greenhouse each day. Whether you are taking them in and out of your house or a greenhouse, it’s a bother either way.

As I’ve gotten older, I like to think I’ve gotten smarter and not just lazier. I realized that I don’t have to start my tomatoes so early. The plants that come from my coldframe are acclimated to the cool soil and to the fluctuations of air temperature from day to night. I can keep the lid on, vent it, or remove it totally, as necessary. I do not put hinges on my coldframe lids for that reason. If they are light enough to be blown off in the wind, I use hooks and eyes to hold them in place. I can start more plants in less space than I ever could starting them under lights in the house.

tomato seedlings started in coldframe, moved to flat

tomato seedlings started in coldframe, moved to flat

Our last frost date here is about April 25. This year, however, frost hit in some places on May 14. It is good to have plants already tuned in to what nature is doing in times like this. A cold snap like that would be more damaging to tender plants raised under lights, than to hardy plants grown in a coldframe. Sometimes I pull plants out of the coldframe and put them in pots or wood flats to finish growing out so that I have room to start more seeds. I only do that if the weather conditions are such that the ones I pull out don’t need the protection of a coldframe anymore. I had done that this year with the tomatoes to make room for the sweet potatoes in the coldframe.

Peppers grow slower and need warmer conditions than tomatoes. When I turned to the coldframes for my transplants I wasn’t sure how it would be with peppers. I’ve since decided that this is a great opportunity to develop a pepper that will grow this way. Otherwise, why would I want to fool with it? If I save the seeds each year, I will have developed a strain that will grow well, no matter what nature brings. I like thick walled sweet peppers and Ruffled Hungarian is one that does well in the coldframe. I originally bought a few locally grown plants at a health food store in 2008 and have been saving the seeds ever since.

It is time to have the tomatoes out of the coldframe, so what’s next? I mentioned that the sweet potatoes went in after the tomatoes. I often don’t plant the sweet potato slips in the garden until about June 7. I’m always anxious, wondering if they will come up in the coldframe or if I should have started the sweet potatoes in jars of water in the house. Then the slips appear and take off. So, if you are anxious, also, have faith. When the weather is right, they will grow. Sweet potatoes like to be warm, so I keep the coldframe lids handy for longer than might be necessary. Learn more about growing your own sweet potato slips at https://homeplaceearth.wordpress.com/2011/04/26/grow-your-own-sweet-potato-slips/

corn seedlings in vole-proof tub

corn seedlings in vole-proof tub

I use transplants for corn and peanuts and worry about voles getting them in the coldframe. Although I have taken measures in building my new coldframes to keep out the voles, I still worry about these seeds, so I start them in large plastic pots, the kind trees come in. I like the kind with a lip on the rim to keep climbing critters out.  These pots are scrounged, I didn’t buy them, and they are useful for many things. When the corn and peanuts are out, I can put other seeds for transplants in there or plant flowers and herbs to enjoy through the summer. Since I’m using them at a time when no protection is needed, I don’t have to worry about a cover. These extra containers are good to have when my coldframes are filled and I want more seed-starting space, once the danger of frost has passed.

Once all the warm weather plants are in the garden the coldframe is the place to start transplants for later squash plantings, more flowers and herbs, or for brassicas plants intended for fall and winter harvest. You no longer need the winter lids to keep things warm, but you might need some shade. If you don’t have shadecloth, you can use an old bed sheet to shelter the seedlings from the sun. The key to this kind of planting is having a plan that shows everything that will be in your garden for the year. For a refresher for that kind of planning, read my post on Making a Garden Map. You will know what you need ahead of time and can plan your coldframe plantings accordingly. My post on Succession Planting will also give you some ideas for using summer transplants.

potato plants to grow out in coldframe

potato plants to grow out in coldframe

If you really aren’t interested in having a continuous supply of transplants though the summer, plant a crop in your coldframe after the last spring transplants come out. I have built a new coldframe to replace an old one and have planted potatoes in it to see if I was successful in keeping out the voles—otherwise, the sweet potatoes would be in there and I wouldn’t have had to put the tomato plants in flats. You could shade your coldframe and plant lettuce or just throw in some buckwheat. In thirty days the buckwheat will be flowering, making the honeybees happy and keeping the weeds away. In early September I plant lettuce in one of my coldframes to provide salads through December. I want that space to be clear for the January/February plantings. I plant the winter greens-kale and collards—under low tunnels. If they were in the coldframes, they would still be there when I wanted to start seeds.

Think of your coldframe as a place to harvest transplants all through the summer, not just in the spring. Consider it an important part of your garden and keep it filled.Homeplace Earth

 

 

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