Spring planning

Under a layer of snow everything seems to be sleeping, even the greenhouses. Inside I've seeded the new years first planting of lettuce and mizuna. Cold winter temperatures mean it won't be ready to harvest for at least a month - maybe longer. Until then I'm busy planning and writing.

Growth rate research questions

Since my growing season is over, and I no longer have any plants in the greenhouse, most of my time is spent organizing data, writing and trying to answer all my research questions.  I have lots of questions.  The ones below pertain only to the growth rate of greens and the economic of growing them because that's what I am thinking about right now.

The first lady knows what low tunnels are!

"I couldn't image how any of our vegetables would survive in temperatures that drop below freezing.  I had heard that some farmers use a plastic covering to extend the growing season into the winter.  But while I was intrigued by the prospect of keeping the garden alive, and I was open to experimenting, I was skeptical that a sheet of plastic would keep the plants warm through the D.C. winter. 

In spite of my doubts, we went ahead and built what are called low tunnels, or hoop houses, simple metal frames that stand about two feet off the ground and are covered by a clear plastic tarp.  To my amazement and delight, under those simple structures, several of out crops continued to flourish, even in very cold weather - and were unusually sweet.  I later learned that since sugars don't freeze, the plants produce a lot of sugars to protect themselves from the cold." 

Michelle Obama in American Grown

plant profile: spinach

Spinach is my favorite green.  


It is not fast growing like some of the brassicas.  Nor does it have sexy colored viens like swiss chard or red russian kale.  Harvesting spinach can be a true labor of love when each leaf has to be cut individually.  Despite all of this, spinach is great.  No, it's beyond great - it is one really cool plant.  Here's why:

~ Spinach is a diecious crop meaning there are male and female plants.  In the absence of any male pollen producing plants female flowers can ‘revert’ to become pollen-producing flowers, enabling continuation of the sexual reproduction cycle.  

~ Spinach is one of the hardiest leaf crops. It grows best in sandy, porous soil but can adapt to a wide range of soils.  Spinach germinates best in cool soil and can germinate at temperatures as low as 35 degrees Fahrenheit.  

~ Spinach can grow at very low temperatures.  Other leafy crops can tolerate the cold but will not grow.  Spinach grown in the cold has higher concentrations of nutrients like vitamin C as well as higher sugar levels.

the wintergreens project

This project is looking at the practicality of growing lettuces, asian greens and other lovely salad greens in UNH greenhouses during the next two winter seasons.


Producing high yields of cool-loving crops would be beneficial for everyone.  Consumer demand for local produce is increasing, especially in the winter.  Most farmers are unable to keep up with the winter demand and can be hesitant to experiment during the cold months when heating is expensive.   


Of course you can grow plants in greenhouses you say- that is the point of a greenhouse.  What we are going to be looking at is how to use greenhouses without adding much additional heat, no additional light and using materials commonly used on a farm.  


On this blog we will be tracking our trials and successes through the winter and spring.     

low tunnels in the greenhouse

Temperature values used are from H. C. Wien's paper
"Use of low tunnels to improve plant growth in high tunnels"

Today we started setting up germination chambers on top of the existing greenhouse benches.  Really our germination chambers are just fancy low tunnels.  Low tunnels are simple hoop structures made from wire or PVC and covered with permeable fabric or plastic.  Their benefits are two-fold for organic and small farmers, they keep insects off plants and warm up the air.  We plan on using the increased temperature to our benefit.

If you put these low tunnels inside a greenhouse or high tunnel (unheated greenhouse) plants are even more insulated from the outside cold.  Our first trials using this arrangement will be looking at the temperature ranges using different materials as covers for the low tunnels.  Permeable fabrics, plastic sheeting and permeable plastic all have their benefits and drawbacks.