If you have been through a season at Stearns Farm, you know that temperature and daylight play important roles in vegetable growth. These factors define when we grow and harvest different plants, but farmers employ several techniques to extend the growing season.
The influence of temperature is pretty straightforward. Every plant grows best within a specific temperature range. For example, lettuce grows best between 60 °F and 65 °F (which is why we have more of it early and late in the season), while tomato plants grow best when temperatures are between 65 °F and 85 °F. Farmers in southern states typically take a break in the summer when daily temperatures are constantly above 90 °F, and farmers in northern states don’t typically grow anything when it gets below freezing, because our usual vegetable crops don’t grow under either condition.
How daylight hours impact growth is a little more complicated. Scientists discovered that it’s the extent of dark hours that predominantly influences plant growth. Some growers use supplemental lighting in greenhouses in the middle of the night to trick plants into thinking that the nights are short (and therefore the days are long), and this way they can get plants to grow as if it is the middle of summer. Since we don’t use supplemental lighting at Stearns, we have other methods to extend the season in order to grow vegetables for our winter shares.
Most plants stop growing when there are less than 10 hours of daylight. Even if they are kept in a climate controlled greenhouse, they will become dormant when the days get too short. In our area, we cross that threshold on November 9, and the summer growing season is officially over then (we’ll have our last summer share distribution on November 1). If we we want to include certain vegetables such as greens in the winter share, we have to make sure the plants have reached maturity before there is too little daylight. We can then use the greenhouses and/or row cover, called Reemay, to protect them from cold temperatures until we are ready to harvest.
This year we hope to have some fresh greens in the winter share, and we’ll be keeping the falling temperatures and diminishing daylight in mind as we plan ahead!
Until next time,