Monday, March 9, 2015

Low Tunnels and Cold Frames

Last week we were bested by the weather, when an unexpected, last minute winter storm covered our garden in a beautiful, but unworkable, blanket of snow. 

Rather than be put out, however, by this burst of cold and the unpredictability of the season's end, we're utilizing some of our finest "who knows what the weather will bring today?" tools! 

So what are these tools you ask? 
Low tunnels and cold frames!

These two handy structures are useful all winter, and into the spring as well. The general idea is that by enclosing a space under clear plastic or glass, the sun's light will pass through, become trapped, and warm the area underneath. This simple process brings many benefits, including...
  • Solarizing the soil! At the end of winter, soils may remain frozen from cold temperatures. This can make it difficult to begin planting. Solarizing the soil with a low tunnel creates warmth that will help avoid both these problems by making the soil workable enough to transplant and warm enough for germination to occur.  
  • Creating livable temperatures for your plants! Even if the soil isn't frozen solid, it may still be too cold outside for plants to survive - particularly at night. Low tunnels and cold frames raise the temperature underneath their coverings - by as much as 30-50 degrees on a very sunny day! - which can make a huge difference for crops. In fact, it's advisable to vent both structures on very sunny days, to avoid overheating your plants.
  • Protect plants from surprise frosts! We've all been there, when you think the cold weather is finally finished, and then one last frost surprises you! Don't let bad weather sneak up on you and harm your plants - low tunnels and cold frames provide frost protection.
  • Enjoy cold weather crops! Some plants actually prefer the cold - spinach, kale, radishes, arugula and lettuce for example. In fact, they taste better if they've been hit by a bit of chilly weather. Utilizing cold frames or low tunnels gives you the chance to start them early so that they get a little of that cold weather that makes them deliciously sweet, but avoid withering during a frost. 
So how do you build these systems?
  • Low tunnel kits with all the necessary components and building instructions are available in the MHC Tool Share, and come in multiple sizes to fit any garden. 
  • Building a cold frame can be as simple as placing four straw bales in a rectangular shape, and placing a glass window pane over the top. 

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