The sweet, ruby red fruit and crimson blooms of the pomegranate (Punica granatum) aren't out of reach for gardeners in cold-winter climates when they bring the deciduous shrubs indoors for the dormant season. Recommended for outdoor planting in U.S. Department of Agriculture plant hardiness zones 8 through 10, pomegranates can take cold temperatures down to 15 degrees Fahrenheit while they are dormant. Because potted plants of any type should be treated as two zones less hardy than the same variety in the ground, you're better safe than sorry when growing a potted pomegranate in a marginal climate.
Hold off on water and discontinue any regular fertilizing of a potted pomegranate as temperatures drop in late autumn to help induce dormancy.
Move your potted pomegranate to a protected area outdoors, such as under an overhang or against a structure that blocks wind, until all its leaves have fallen. Grouping potted plants together also gives them some protection from wind and cold.
Bring your pomegranate indoors before your area's first hard freeze. A hard freeze is an extended period below 32 F. The ideal location is unheated, but stays between 30 and 45 F and allows in sunlight. Mediterranean natives such as pomegranates need cool, bright winters. Possible overwintering sites include a three-season sun porch, garage, basement, unheated greenhouse or hoophouse.
Water the potted pomegranate until the top inch of soil is wet approximately once a month.
Vent the overwintering space or move the plant to a cooler location if the temperature inside rises above 45 F as spring approaches and outdoor conditions are still cold. Shrubs that overwinter indoors tend to break dormancy easily once they have met their chill requirements. Depending on variety, pomegranates require from 100 to 200 chill hours -- hours below 40 F -- to set fruit.
Move the plant back outdoors in the spring once danger of frost has passed, setting it outside for a few hours each day. Increase the time each day over a week to 10 days, until it can stay out all day.