Winter watering is something that stumps many people. If you think about it, most of us put the hose away in late October or November when we begin to have frosty nights. Hoses may not come out again until late March or April.
In the meantime, we have really windy winters when the ground is frozen and plants stand no chance of replenishing moisture loss. That is ½ of the year without water! When I ask people if they would do that to their Aunt Tillie they get a look of horror. Often their response is, “But the plant is old, so why would it need water?” Old people need water, why wouldn’t old plants? They especially need water! They are weaker and have a lot of foliage.
So here are the rules:
1.) New plants that do not have a full root system will need supplemental water in the winter. How much depends upon how new they are. If they were just planted this year, perhaps as often as every couple of weeks in fall and once a month in winter if the ground is thawed enough to accept water. This should likely continue for the first couple of years. The larger the evergreen leaf, the more wind resistance, and the more likely it will need water frequently. Smaller leaved evergreens, needled evergreens, and deciduous plants need less frequent water. I tell people to do occasional watering through December. In January you may get a run of a few days where the ground thaws enough to accept water. Again, in February, you may get one or two opportunities. By March we are usually starting back into some rains so you will have to monitor the weather and water accordingly.
2.) Just because there has been rain does not mean the plant has had any water. Nursery mixes are a very different structure than the surrounding native soil, so be sure to water into the original root ball and beyond. There is little lateral movement of water from the native soil into nursery soil. Plants cannot really pick up water well until they get a substantial number of roots into the native earth. A good time to water the nursery soil is after a rain when the native soil is wet. This encourages the roots to escape the pot size and get into the native earth.
3.) Very large leaved evergreens like aucuba and Southern magnolias may benefit from a fall application of an anti-transpirant (sometimes called an anti-desiccant). Several brands are on the market. They put a spray cover on the leaves to seal up the breathing holes a little so they do not lose so much moisture to wind. Be sure to follow label directions regarding freeze after application.
4.) Evergreens can die during the winter and seemingly be in suspended animation until spring, when they suddenly show symptoms and collapse in just a few week’s time. One minute they look fine, the next they turn brown.
5.) Beware killing it with kindness. While some water is needed when it can percolate out of the hole, watering enough to make it stand at the root ball or when the ground is too frozen can backfire. Root rots can establish. It is helpful to look up whether your particular plant is susceptible to root rot.
So, don’t be afraid to water in the winter. You will likely do more good than harm. Plants, like all living organisms, appreciate some water, even when they are dormant. It keeps the fine hair roots pliable and doing their job.