While I hope for a wet winter, forecasts have been conflicted on what to look forward to for moisture this winter. I would mark it on the calendar to water the following plants, so that way in spring they ready to grow again vs recover from any drought damage sustained over winter.
Who Needs a Drink?
Any Plants in Pots (check weekly)
Newly Planted and Established of the following plant families (check every two weeks, generally water monthly); Arborvitae, Fir, Juniper, Spruce, Pine, Evergreen Magnolia, Laurels, Rhododendrons, Azaleas, Hemlock, Boxwood, Hollies, Blueberries, Japanese Maples, Pacasandra, Cedar, Cypress, Hinoki Cypress, Mountain Laurel, Western Red Cedar, Pieris, Andromeda, Umbrella Pine and Yew.
How to Water in the Winter?
The most convenient way to water plants in the winter is a sprinkler on a hose. Let it run for 30 to 60 minutes, depending on soil type and size of plant, per tree or garden bed. Just remember when done with watering to disconnect the hose from the faucet and drain the hose. You may also bucket water to plants as well, 5 gallons keeps small bushes hydrated while larger shrubs and trees need much, much more.
When to water?
I don't water when the ground is frozen, I water when the daytime temps are in the upper 30s and 40s. It won't hurt plants if it gets colder at night because the ground temperature will keep the water from freezing.
How to check?
If in doubt about if a plant needs water, simply dig into the soil within it's root zone. I like to go down at least 6 to 12 inches to verify soil moisture. If it's dry, I water.