Cutting Lettuce in December

Simpsons Curled (left) and Red Sails lettuce
cut December 2

We’ve had many hard frosts during the last few weeks.  One morning the temperature was 27°F at dawn.  Many mornings our lawn is frosty white.  What am I harvesting from the outdoor freezer?

“Bob, we’re out of lettuce.  Do you still have some in the garden?”  Ellen recently asked.

I went to the garden and brought in the last of the lettuce I had planted in September in the experimental greenhouse or lettuce box—the one I called a “greenhouseperhaps” in an earlier posting—a bright-green Simpsons Curled plant and a Red Sails.  After I washed both lettuces, I stored them in a large plastic bag in our refrigerator between sandwiches and salads.

Red Sails seedlings in "greenhouseperhaps"
in early December

We’ve had such a warm fall that in early November I removed the box from around the lettuce and moved it to another location to protect three just-sprouted Red Sails plants, which continue to grow slowly.  This is a first-time experiment to see how long lettuce can continue growing as late-fall temperatures work their way down the thermometer.  Will some super-cold night soon kill the young plants?  Or will I pick lettuce at Christmas or New Year’s—or beyond?

What have I learned so far from this experiment?

First, with a little thought and care, I can pick lettuce—often called a “cool weather” vegetable—during most of the year if I plant small, successive crops every two to four weeks.  If I plant seeds in mid-March, I can begin picking small leaves as I thin the plants in April.  From May through November I can pick beautiful, mature plants.  Photo 1 shows the two beauties I picked even later, on December 2.

Second, my small greenhouse experiment quickly taught me that “short” lettuce will grow best in the box’s limited height.  Simpsons Curled and Red Sails top out at a foot or more, taller than the box.  When their leaves touch the top (lid) of the box, where moisture collects and freezes on frosty nights, ice crystals sometimes encase and damage the tallest lettuce leaves.  This winter I must buy a packet of seeds of some “short” head or leaf lettuce that will grow in the box without pressing against the icy top.

Third, the “greenhouseperhaps” is small, so the number of plants that can grow without overcrowding is limited.  For my first crop I transplanted 10 times too many plants and seeds in the box—a row of Simpsons Curled plants and a row of Red Sails seeds.  Within a few weeks the Simpsons Curled covered the Red Sails sprouts, which suffered in the deep shade.  My second attempt (Photo 2) has just three Red Sails seedlings, which I started in our sunroom in yoghurt cups and then transplanted.

Will I pick lettuce at year end—or even in early 2012?  I’ll let you know what happens as increasingly cold weather impacts on the three Red Sails lettuce plants growing in the mini-greenhouse.