A later-than-normal polar vortex combined with cool air and moisture will bring cooler nighttime temperatures in the coming days, including the possibility of near-freezing temperatures this weekend. ConnectLocal offers tips on protecting plants that may be coming up in new gardens seen popping up throughout Toccoa/Stephens County.
Weather forecasts from the National Weather Service indicate that a front of cold air and moisture is set to combine with a polar vortex, potentially changing the famed May showers into freezing conditions and even the possibility of snow in sow regions of the Northeast.
The weather pattern emerging from the mix of these conditions will be what meteorologists call a closed low-pressure area in the jet stream. This occurrence if common during early spring, and often results in deep freeze conditions and snowstorms throughout the eastern seaboard in January and February.
However, the magnitude of the pattern coming up, and the resulting blockage of the jet stream, happens perhaps every 15 to 30 years this late in the season.
Heading into next week, weather experts are expecting this to be “that year” for a large swath of the Northeast – with snow a possibility across a 500-mile region from Northern Ohio to Eastern New England. This system is not a “weekend fluke” either. Periods of freezing temperatures are forecast for parts of the interior Northeast into the middle of May.
While that may not seem significant to us here in the deep south, we are not escaping this weather pattern. Weather maps show cold temperatures – anywhere from 15-25 degrees below normal – curving above the jet stream, which dips down nearly to the North Carolina/Georgia border.
“Saturday and Sunday, unusually cold air moving into the area will lead to the potential for frost to develop in the early morning hours,” states a NOAA National Weather Services hazardous weather outlook for the Stephens County area.
That forecast may spell disaster for some gardeners, farmers and vintners alike. Plunging temperatures could cause damage to sensitive stock, recently bought plants, vineyards and orchards.
According to the UGA Extension office, efforts should be made to protect plants if temperatures drop below 32 degrees. A moderate freeze with temperatures in the 25- to 28-degree Fahrenheit range can be widely destructive to vegetation.
Frost injures plants by causing ice crystals to form in plant cells. This makes water unavailable to plant tissues and disrupts the movement of fluids. Frost-damaged leaves appear water-soaked, shrivel and turn dark brown or black.
Plants are classified according to the minimum temperatures they normally tolerate. "Hardy" plants tolerate some amount of short-term freezing, while "tender" plants are killed or injured by freezing temperatures. Citrus, avocados, bougainvillea, fuchsias and succulents are among the tender plants.
Marin Master Gardeners gives the following advice:
Water the soil thoroughly (except around succulents). Wet soil holds heat better than dry soil, protecting roots and warming air near the soil.
Bed sheets, drop cloths, blankets and plastic sheets make suitable covers for vulnerable plants. Use stakes to keep material, especially plastic, from touching foliage.
Remove the coverings when temperatures rise the next day.
For a short cold period, low plantings can be covered with mulch, such as straw or leaf mold. Remove once the danger of frost has passed.
Place a 100-watt lamp designed for outdoor use in the interior of a small tree. It can emit enough warmth to reduce frost damage. Holiday lights (not the LED type) serve a similar function, but be sure they don’t touch any covering materials.
Spray an anti-transpirant, available at your local nursery, on the foliage of cold-sensitive plants to seal in moisture. One application can protect up to three months by coating the leaves with an invisible polymer film.
Cluster container plants close together and, if possible, in a sheltered spot close to the house.
Succulents need special care While some succulents like stonecrops are very cold hardy, others are quite sensitive. If the temperature frequently dips below freezing in your microclimate, you may want to keep your succulents in pots so you can move them indoors or to a sheltered location under house eaves, a deck or a tree. Whether your succulents are in pots or in the ground, try to keep them on the dry side. When plant cells are plump with water, they are more likely to burst if the water freezes. Do not remove damaged leaves unless they start to decay. Leaving them in place protects lower foliage. Don’t overreact to plant damage Plants can be remarkably resilient. If you see signs of frost damage, do not prune off the affected parts or dig up the plant immediately. This is especially true for palms. Wait until the weather warms up in March to see whether new leaves sprout. You may see healthy new growth at the base of the plant, at which point you can prune out the damaged parts. If no regrowth is noted, remove the dead specimen and replace it with a more cold-tolerant species.
FYI - What is a Polar Vortex?
The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. It ALWAYS exists near the poles, but weakens in summer and strengthens in winter. The term "vortex" refers to the counter-clockwise flow of air that helps keep the colder air near the Poles. Many times during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream (see graphic above). This occurs fairly regularly during wintertime and is often associated with large outbreaks of Arctic air in the United States. The one that occurred January 2014 is similar to many other cold outbreaks that have occurred in the past, including several notable colder outbreaks in 1977, 1982, 1985 and 1989.
There are several things the polar vortex is NOT. Polar vortexes are not something new. The term “polar vortex” has only recently been popularized, bringing attention to a weather feature that has always been present. It is also not a feature that exists at the Earth’s surface. Weather forecasters examine the polar vortex by looking at conditions tens of thousands of feet up in the atmosphere; however, when we feel extremely cold air from the Arctic regions at Earth’s surface, it is sometimes associated with the polar vortex. This is not confined to the United States. Portions of Europe and Asia also experience cold surges connected to the polar vortex. By itself, the only danger to humans is the magnitude of how cold temperatures will get when the polar vortex expands, sending Arctic air southward into areas that are not typically that cold.