Frost Irrigation

When temperatures fall to freezing we need to protect the small buds that have this seasons growth. We do this by irrigating. When the water changes from liquid to a solid (freezes) it gives off some heat. This heat, though small, is enough to keep the plant from freezing. In the fall, we do the same thing.

In the morning the ice will still be on the vine and we need to keep irrigating until it melts. Later in the summer the heat of the water will be enough to warm up the whole farm and there will be no ice. Because it is open and low lying, we have had frosts as late as July 4, and as early as August 14. This means lots of work. We monitor the weather closely and have an annunciator system that can tell us the temperature or provide an alarm if it gets too cool.

We have 68 acres of cranberry and 400 acres of supporting land. This is land that gathers water for frost irrigation and flooding, land where we can spill water, and upland that provides habitat for all sorts of animals. In the morning there are often deer tracks. When the day warms the herptiles (frogs, snakes and turtles) come out.

Flooding

Flooding is an important part of cranberry management. In the spring we flood to protect the vine from cold weather. Once it warms up the flood is withdrawn and the vine can begin growing. We install an irrigation system at this point. When we get cold weather later in the spring, we run the irrigation system to protect the plant from frost.

The vine is hardy to about 20F when it is dormant, but as soon as it starts to grow the tolerance is about 29 1/2F. The irrigation system spreads water on the vine. The water has some latent heat which warms up the vine. Once it has given up most of its heat and freezes it gives up more heat (the change of state liquid to solid) to the vine. As long as you keep irrigating, the vine will now be damaged. Needless to say... cranberry farmers always watch the weather and get poor sleep in springtime.