Overwintering (Dormancy)

Overwintering Temperate Carnivorous Plants in New England

Written by Michael Stiffler – mstiffler.necps@gmail.com

New England Carnivorous Plant Society – www.NECPS.us

General information

Temperate carnivorous plants require a cool winter dormancy period, this includes all North American carnivorous plants: Venus flytraps, Sarracenia, and temperate sundews (eg. D. filiformis). Carnivorous plants that originate in climates with cold winters and shortened daylight periods stop actively growing during this time. In the spring, as weather warms up and the daylight period lengthens, the plants resume growth. Improper overwintering is a common reason for failure with temperate carnivorous plants. The plants should experience a decrease in watering, photoperiod, and temperature. Temperatures above freezing to 50 ºF are ideal, although most plants will survive brief periods below freezing. In New England, temperate carnivorous plants are best grown outdoors, but special accommodations must be made for overwintering as temperatures here are too cold. Typically, the dormancy period lasts from November through March in New England, but varies by location. Here I describe some techniques for overwintering.

Garage method

This method requires access to an attached garage, which receives some heat from the house and protection from freezing winds. Temperatures above freezing to 50 ºF are ideal. Simply place plants in a convenient location in the garage, in front of a window if available. Stand-alone shelving can be used to better optimize floor space for larger collections. If using the tray method, keep the water level shallow. On strings of very cold days, if the temperature in the garage is expected to fall much below freezing, bring the plants inside the house for that time. Alternatively, I’ve had success carrying out dormancy in an unheated basement. This method is good for collections of all sizes, even single pots.  

Mulching method

In this method, the plants are kept outside but protected from the cold by a thick layer of mulch (preferably pine needles). If thick enough, the temperature inside the mulch bed will remain above freezing even on extremely cold days. The approach is to first construct a walled barrier large enough to hold all the plants plus a layer of 1-2 feet of mulch on all sides and top – this can be built using stakes and burlap. Place the plants inside the barrier, and cover plants with burlap to make removal of mulch from the plants easier in spring. Finally, add a dense layer of 1-2 feet of pine needles on all sides and top, the thicker the better. Importantly, this structure should be built on the ground, as warmer temperatures from underground rise up and are trapped inside the insulated mulch layer. In spring, remove the mulch and burlap. This method is best for bog gardens and large collections.  

See the NECPS care sheet “Outdoor Dormancy, My Technique” by Bill Matthews for pictorial step-by-step instructions and additional tips.  

Refrigerator method

Generally, this method involves uprooting plants and clipping all leaves, dusting plants lightly with fungicide, placing plants individually or in small groups in plastic bags, then placing in the refrigerator. Alternatively, plants can be left in their pots and covered with plastic bags. Check plants periodically for dryness or fungus. I advise against this method unless no other option is available; I’ve experienced frequent losses especially with smaller plants.

New England Carnivorous Plant Society – www.NECPS.us