Winter Hardiness

OLYMPUS DIGITAL CAMERAThe significantly colder than normal weather we have been experiencing during February 2015 is a good reminder that an important key to success with landscape plantings is choosing plant varieties that have enough winter hardiness to prosper in the locations where they are planted.

The genetic makeup of each plant variety is usually the first thing we think of when we consider winter hardiness and good, tough cold climate genetics are truly very important.  Without a good set of cold tolerant genes, perennials, shrubs and trees are unlikely to succeed in a Minnesota landscape.

Another factor in improving winter hardiness is good site selection.  A plant that can tolerate cold temperatures may fail if it is planted where it has too much exposure to winter sun bouncing off snowbanks, and too much exposure to fierce winter winds.  The same plant may perform really well when planted in a location where there is some protection from the worst of the winter winds, and where long winter shadows prevent most of the winter sunlight from repeatedly striking the bark of the trunk, twigs, bark or the needles of certain varieties of evergreens.

Other factors that can enable a landscape plant to avoid winter damage are the soil pH, proper soil drainage, absence of soil compaction, the amount of organic matter in the soil, and the amount of sunlight the plant receives during the growing season.  If a plant is completely happy going into the winter, it is more likely to have little or no winter damage.  Plants that are stressed by unfavorable site conditions are far more likely to suffer winter injury.

The Northfield area currently has a Zone 4 hardiness rating.  Zone 3 covers most of the northern half of Minnesota.  Most trees, shrubs and perennials rated for Zones 4, 3 and 2 will over-winter quite well here without injury.

Quite a few plants that are rated as hardy in Zone 5 will do well in the Northfield area IF they are planted in rich, fertile, soil with ideal pH, good drainage, protection from winter winds and protection from winter sun, and if they get adequate sunlight during the growing season.  Quite often these borderline hardy landscape plants can give 5, 10, 15 or even 20 years of good service in the Northfield area despite the fact that they are rated as hardy only to Zone 5.

If this all seems confusing, we stand ready to help you sort through the varieties and site conditions to avoid winter injury.  Call us or stop in for a visit during April when our plant materials will be uncovered and available for sale.  We’d be happy to show you around.