Bring on the Brrrrr

Plants are rated for hardiness according to the Plant Hardiness Zone Map, which was revised in Canada in 2000. The map has nine major zones - the harshest being 0, the mildest being 8. The lower the number the tougher the plant is. Plants rated as being able to handle Zone 1 will survive in areas with temperatures as low as -45.6 Celsius.

These hardy individuals may as well have antifreeze flowing through their cells. Cold hardiness is of tremendous interest to agriculture worldwide. The addition of cold hardiness genes to food crops can extend the harvest season, allowing for greater production.

Each year the International Plant Cold Hardiness Seminar is held in a different part of the world. Scientists have determined that cold hardiness is a quantitative trait. Molecular evidence indicates that development of cold hardiness or cold acclimation is a complex phenomenon involving changes in gene expression that result in the alteration in metabolism and composition of lipids, proteins, and carbohydrates.

The zone range in Nova Scotia is from 5a to 6a, thus those plants that are hardy to zone 2 or below, should have a very easy time of it here during winter.

These species include trees such as the paper birch, (Betula papyrifera), white spruce, the Eastern larch (Larix laricina) and quaking aspen. Some of the super hardy shrubs are: rugosa rose, common lilac, juniper, mugho pine and Siberian pea shrub, viburnum and potentilla.

Zone 2 perennials that can stand the worst that winter can dump on them include peony, monkshood, summer phlox, oriental poppy, snow-in-summer, sea thrift, windflower, Siberian iris and lady’s mantle.

Some of the best Zone 2 Explorer roses include ‘David Thompson’, a medium-sized shrub that reaches a height and diameter of 1.2 meters. This plant produces fragrant, medium red flowers seven centimeters in diameter with an average of 25 petals. ‘Henry Hudson’ is a rugosa hybrid that flowers repeatedly and is highly resistant to blackspot and powdery mildew. The fragrant flowers are white with a pink tinge resembling apple blossoms. ‘Adelaide Hoodless’ is a floriferous, vigorous shrub rose with large clusters (up to 35 blooms) of seven cm., semidouble, red flowers in July and September. This plant grows to about one meter with arching stems.

If you live in an exceptionally challenging area with little protection or right on the coast, any of the above plants may survive where others have died in the past.