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Unusually warm temperatures last fall, followed by frigid weather in December and January, could result in some interesting revelations come spring. What might we expect as we thaw?

A rather warm late fall/early winter may have confused many plants in the landscape. Plant dormancy is triggered by changes in both temperature and day length. While length of day is driven by the earth’s trip around the sun – something we can depend on – the unusually warm temperatures might have muddled things a bit.

Woody plants require chilling to halt new growth until spring. The number of hours required for chilling varies with plant species. Warmer temperatures cause plants to begin growth. Once plants start to grow, they are less able to readjust as temperatures become colder. Although growth is apparent to us when buds swell and green tissue emerges, plants began growing before bud swelling was evident.

Our unusually warm weather brought about bud swell in some plants. I even had a few blooms on one of my forsythia shrubs. Some of my perennials continued growing much later than normal, as did the annuals – remember how long the summer container pots lasted? They went on and on and on, into November. I finally got tired of watering pots and let them go. (Clearly, my temperament is not suited to gardening in a region with no winter.)

I saw no bulb activity in my garden. Even if there had been, bulb plants are less adversely affected by late-season warmth. If bulb foliage grows, it may sustain surface damage from the change to cold temperatures, but the flower is safe underground.

Lack of moisture might be the bigger issue. With below-normal precipitation late fall into early this year, frost may have penetrated deeper into soil, which can result in frost heaving. (If you see plants thrusting up out of the ground, it’s frost heaving.) This kind of damage is generally irreversible because roots can become exposed during the heaving.

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Lack of moisture, little to no snow cover and frigid temps in December and January can all lead to bad things happening under the soil. Snow makes great soil insulation. I like to think of it as winter mulch. Unfortunately, without snow cover, extreme cold temperatures can freeze soil much deeper, damaging root systems of trees, shrubs and perennials. Snow also helps conserve soil moisture over the winter and provides moisture as it melts.

On the bright side – is there one? – the extreme cold period at the end of December and beginning of January may – we can only hope – at least put a dent in the number of nasty pests. Some of our pest issues have reportedly been due to lack of frigid weather in recent winters.

If we’re lucky, perhaps we had just enough cold to kill off some pests but not kill our plants.

Time will tell.

Mari Lane Gewecke is a Master Gardener volunteer, affiliated with the University of Nebraska-Lincoln campus program, and a self-employed consultant.


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