Cold Frame Corner: Final Installment (Part IV)

Written by: Susan Perry, Larimer County Master Gardener

This is going to be my final blog about the cold frame experiment.  Not that we’re done – we still have spinach, carrots, and beets to harvest, probably till March – but simply because we’ve probably learned all the lessons and made all the adjustments that will come up this year.  In fact, Tom just harvested more spinach to make another batch of his home-made, from scratch family ravioli recipe.  Yippee!

 

The cold frames. 

Temperature:  We’ve dealt with brutal cold by using incandescent Christmas lights under space blankets draped over wickets.  Initially, we had lights on timers and adjusted the length of time that the lights were on.  More recently, I found a “thermocube” outlet online that’s available locally – it shuts off the lights at around 45 degrees and turns them on at 35 degrees.  It’s always plugged in, doesn’t require a time, and cost under $15.  It’s not super-precise but will work fine for our purposes.  I expect lettuce and spinach will be happier within this general temperature range and the goal for the carrots and beets was simply to prevent the ground from freezing.  The inclusion of space blankets makes a huge difference in retaining heat, plus they’re easy to store.  We use clothespins to attach them to the wickets.

 

Using Christmas lights to raise the temperature in the cold frames.

Wind:  We’ve dealt with wind, which blew off the cold frame tops when they were anchored by a lengthwise piece of wood with a half-size concrete block hanging from both ends.  Full sized concrete blocks worked well but were hard for one person alone to remove and replace every morning and afternoon.  So we went with two ratchet straps running lengthwise on each box, which have worked perfectly and are easy for one person to work with.

Mud:  Note to self – stepping stones between the cold frames for when the snow melts, instead of dealing with a mud pit!

Veggies:  Next year, we’re going to plant more lettuce and spinach and fewer beets.  We just can’t find enough recipes with enough variety for so many beets.  Carrots have worked well– for whatever reason, even though we usually roast them, we’re not bored.  But I think if we looked for more recipes, we’d find them.  Finally, the leeks.  Well, we lost most of them, harvested & froze those we could save.  I’d plant them again but we realized we have to remember that the cold frame for them has to be much taller.  So that cold frame might take two space blankets and might require other adjustments to keep them alive.  Raised beds might lend themselves to leek cold frames, if the leeks were planted deep enough.  A cold frame could be set directly on top of the raised bed.  We have a lovely potato and leek soup recipe that we enjoy and I’m sure there are many others we could take advantage of.  Other possible vegetable candidates we might consider in the future would include onions.  We’ve never tried parsnips but our handy carpenter friend Ted raves about them and both parsnips and onions would be similar to carrots, in that we’d just be preventing the soil from freezing.

 

Carrots harvested February 4, 2015.

Vacations and Automation:  One hope we had when we started was that we’d be able to automate everything in case we wanted to take a vacation.  If you’re an avid gardener, when do you take a vacation?  Spring is starting plants inside; summer is work outside; fall is harvests and fall crops; winter could include cold frames.  I read about an automated venting arm gizmo that is used in greenhouses but after this winter’s winds (and our many failures), I suspect that an automated venting arm and the tops would blowing to Kansas even if heavy-duty hinges were used.  One possibility would be a venting arm that used both temperature AND wind to determine when to open and close, but I expect it would be fairly expensive.  Besides, the space blankets provide BOTH cold and heat “protection”.  We know this because we had a few weeks when we felt lazy and didn’t remove the cold frame tops – with no negative effect.

Other Lessons:  The polycarbonate for the tops of the cold frames was very expensive and had little R-value.  But their benefit when compared to glass storm windows is that we don’t have to worry about safety/broken glass.  Time will tell if their useful life will be cost effective in the long-run.

 

Carrots growing in the cold frame.

What’s Next:  We’re planning on using the cold frames to warm the soil early in the spring and get an early start direct seeding some veggies (mostly cold season veggies).  We’ll try to incorporate the lessons learned from this winter into next winter’s efforts.  And I’m planning to munch on Tom’s second batch of his yummy spinach, mushroom, and cheese ravioli in the coming months!