During the months of April, May, and June, the cranberry plant moves from winter dormancy allowing the bud to transition its development into uprights with flowers and fruit. A critical growing practice at this time is to monitor the growth of the cranberry vines by observing the vine’s pigmentation and the development and coloration of the bud at the end of upright vines. These clues give an indication as to what temperatures the plant will be able to withstand before a fatal frost sets in.

Cranberries have a temperature tolerance at which the plant can withstand damage from frost. This tolerance changes as the plant matures each week during the spring growth spurt. A cranberry farm can loose their entire income for two years from severe frost damage, with damaging frost occurring in less than 20 minutes if not protected. It is not unheard of to have up to 30 nights of damaging frost during the spring growing season. By irrigating their bogs with water during a frost event, the layer of ice that forms over the vines actually protects the plant from the killing cold temperatures.

A relatively new technology to the cranberry industry, automated irrigation systems enable growers to automatically turn on and off their irrigation pumps.  These systems use sensors placed within the cranberry vines to monitor temperature and other weather conditions. These systems are fully-controllable via the Internet and growers can log onto a secure site to monitor and manage each pump.  On average, a recent survey showed that growers utilizing automated irrigation systems can save more than 9,000 gallons of water per acre on a frost night.  In addition, there are substantial savings in the amount of wear on the pumps, as well as on labor and fuel costs.

View a slideshow on spring frost in cranberry agriculture

• Cranberry bog after frost event; April temperature dropped to 15 degrees F.
• As of April 20, cranberry bud will tolerate no less than 20 degrees F. To our readers please note:all dates are approximate, each growing season can vary the development of the plants,plus/minus 10-15 days.
• As of May 1-15, bud will tolerate no less than 27 degrees F.
• As of May 15-June 10, new growth will tolerate no less than 29.5 degrees F.
• As of May 28-June 29, developing flower will tolerate no less than 30 degrees F.
• Bloom Stage: Approximately June 20-July 15, plant will tolerate no less than 30 degrees F.
• Helping the environment, growers utilize laptops and the internet to monitor weather conditions on the bog. These systems save on water, fuel and labor.
• Cranberry pump house with weather station.
• Automated irrigation systems tie into conventional irrigation pumps and can save thousands of gallons of water on a frost night.
• Bog side weather equipment can monitor temperature, soil moisture and more.
• New technology, such as pop-up style sprinkler systems, conserve water.