Sunday, August 2, 2015

Is This Plant Really Hardy to Zone 4?

Those of us in northern climates always check the rated hardiness of plants we buy to make sure they can survive the cold winters. I live in a borderline area that is zone 4 to zone 5. I also live on top of a mountain which tends to cause about a two week delay between when plants bloom a couple miles down the road at the base of the mountain and when they bloom in our yard. All of which means I look for zone 4 hardiness whenever I add plants to the yard.

But just because a plant is rated for zone 4 doesn't mean that it is comfortable in zone 4 climates. Forsythia bushes, for example, grow very well in our yard and around much of New Hampshire without fear of being killed off by cold temperatures. A late frost or excessively cold spell during the winter, however, may mean that the forsythia will not produce any flowers, or very few, during a particular spring.

The same is true of many fruit trees that are supposed to be safe for zone 4. Some peach trees, plum trees, and other varieties may suffer from the same late frost damage that forsythias may experience. If this happens, they may have no blossoms at all in a given year, and, therefore, no fruit at all in the fall.

If you have fruit trees that produce fruit some years and none in others, it may be a result of the tree being planted in a zone that pushes the limits of it cold tolerance. The tree generally isn't hurt by the late frost or winter cold snap, so technically it is hardy for the region, it's just that it may be unable to produce fruit or flowers unless the winter weather has been particularly favorable.

This year turned out to be one of those years for us. We have loads of developing apples and grapes, but the forsythia, peaches and plums never blossomed at all. Their tender flower buds having been nipped by Jack Frost. Covering them with a thin, light tarp or plastic sheet would probably have helped if we could have predicted the coldest weather or the rogue late freeze. Such covers help trap ground heat and form a protective temperature barrier around the covered plant and will also prevent frost from precipitating directly on the plant.

If you do elect to cover them, just be aware that the covers can also catch snow and become far too heavy for the plant to support. This can cause broken branches or even snapped trunks completely destroying the young fruit tree.

Choosing plants that are hardy to one zone beyond where you live will help ensure that they produce regularly. If you must have peach trees or other semi-hardy fruit trees in New Hampshire or other northern climes, choose a hardy variety, such as the Reliance Peach, and understand that unless you take precautions to protect them, you may have some years of little or no fruit production.