Winter is here. I know there are a lot of people who love winter. I’m not one; I prefer summer.

Animals adapt to winter in multiple ways, hibernation, migration, etc., but what about the trees? We basically have two kinds of trees; deciduous trees like ash, cottonwood and oaks and evergreens like the blue spruce and pine trees. In late fall the deciduous trees absorb all the valuable materials out of their leaves and allow what’s left to die and drop off. Then they go into a time of no activity and live off the stored nutrients in their roots. The bark is fairly thick in most mature trees, but here in Nebraska the water carrying tubes in the tree still freeze and break thus no water is going to the limbs and branches. Come spring the tree will re-grow the water tubes and the cycle stars again. It’s different with the evergreens. Evergreens fight through the winter.

The pine needle is a compact leaf with a thick waxy covering that protects it from the cold. Chlorophyll, the green pigment found in leaves responsible for the process of making sugar, is not absorbed but continues to make sugar throughout the winter, albeit not very much. Like the deciduous trees, the thick bark of the evergreen tree protects it from the cold of winter and the water tubes in the evergreens have safety valves to protect them from freezing, unless you reach a minimum temperature.

But what is that minimum temperature? The USDA has a Plant Hardiness Zone map that tells you what plants will grow in your area. Gothenburg is in Zone 5 which means that the average lowest temperature over the winter is between -10 degrees and -15 degrees. Once Gothenburg was in Zone 4 where the average low temperatures are -20 degrees or -25 degrees. However, due to the “recent” warming trends, those zones have been adjusted.

The average low temperature isn’t as important to the trees year-to-year as is the actual lowest temperature for that year. What happens if this year we get a -30 degree night? The record low for February is -35 degrees, set on February 12, 1899, so it is possible to have a night that cold.

If the temperature drops below -25 degrees for a single night, we won’t have any peaches next summer (which has happened the last two years), but most of the trees will survive. If it stays that cold for any length of time, we can experience “winter kill”. We can also have winter kill if it gets too dry. Recall that pine and spruce trees continue to need water in order to make and metabolize sugar all winter long and if there isn’t sufficient water, they suffer. Also, the roots of the deciduous trees are still active below the surface and they need water.

It is not only trees that can suffer from insufficient water in the winter. People also suffer when it gets cold and dry. We don’t think about the importance of water to trees or ourselves in the winter, but water is just as important now as in summer.

So, now that winter is here, change the furnace filter, bundle up, get the fire started and make sure to drink plenty of water…