The chilling November freeze from a few weeks ago has faded into memory, but it’s certainly become a part of Colorado’s record books. While compared to the Halloween freeze of 1991 – which resulted in thousands of dead Siberian elms throughout eastern Colorado – this storm system was far more severe.
The National Weather Service Station in Denver measures temperature severities in three-day increments. In 1991, the high was 71 degrees on October 27, and then dropped to a record low of 7 degrees on October 29 – a 64 degree decrease in temperature.
In 2014, the high was 64 degrees on November 10, and then dropped to a record low of -13 degrees on November 12 – a 77 degree decrease in temperature. This was the third largest temperature drop ever recorded in the Denver area – February 1951 saw the greatest at 80 degrees; January 1961 came in second at 78 degrees.
Perhaps most environmentally alarming is that three of the largest temperature drops every recorded in the Denver area occurred during the last 12 months:
- December 2013 at 75 degrees
- January 2014 at 72 degrees
- November 2014 at 77 degrees
Interestingly enough, temperatures leading up to the November freeze were continually on the rise:
- September temperatures were 1.4 degrees above average
- October was 4.3 degrees above average (setting several records)
- As of November 10 temperatures rose 7.6 degrees above average
Until November 11, when the temperature hit a bone-chilling 7 degrees, there was not a hard frost reported along the entire front-range.
So what does this mean for our Colorado climate? The short answer is we really won’t know until the spring of 2015.
What we do know is that the freezes of December 2013 and January 2014 caught many pine and spruce trees along the front-range off guard. This resulted in brown and frozen foliage, which is clearly evident by the early spring of that year. Spruce and pine trees rely heavily on the most recent three to five years of foliage, and while many recovered with new growth, the previous year’s foliage was damaged or lost. Essentially, evergreen trees and many others went into winter dormancy in a weakened state.
We also know that many plants haven’t yet dropped their leaves prior to the November freeze of 2014 – leaving many shrubs, fruit trees and especially roses at high risk of freeze damage. Trees that already saw their share of struggles in 2014 – hybrid cottonwood, aspen, red maple, ash – are also at a higher risk of damage from the blistery cold temperatures.
One obvious sign of such damage is evident by leaves that are still clinging to trees. When trees are drought stressed, mineral deficient or weak due to damage, they do not build sufficient carbohydrate storage in the wood – preventing leaves from fully hardening off for winter. The result – the freezing point of the cells is not low enough, and so they freeze and burst instead.
What can you do now to help combat the effects of Colorado’s most recent November freeze?
- Insulate the soil around tree bases in order to better protect root growth during the dormant months. Mulch areas in beds and around trees that are bare – bare soil does not retain temperature to help protect roots from freezing.
- If the weather does turns dry, we suggest winter watering. Dry soil loses heat much more rapidly than moist soil. Additionally, drought stressed trees and shrubs are more prone to freeze damage.
Colorado winters can be difficult for your landscape – let Swingle be the caretakers.