It may seem somewhat surprising to think about watering plants when life is cold and dormant in the winter, but depending on your USDA zone and where you are growing, there are different approaches and reasons to keeping the soil hydrated in the cooler months.
It way seem counter-intuitive, but one way to protect your plants over winter if you live in a zone with a hard freeze is to create a bit of an “ice cube effect” in the soil. This means giving a deep watering just before the ground freeze hits. In spring, your garden will thank you as the water resources needed to kick-start growth are already right there in the soil.
If your climate is a little temperamental and has a few freezes and thaws over the course of the winter, the best water resource is snow: pile snow on all of your gardens, which will both insulate them from the cold and dry effects of frost, and also provide the roots with water during the warmer periods where plant tissues may “wake up” a little bit.
In zones with a mild winter, precipitation usually provides sufficient watering, although plants in pots can use the occasional moisture-boost. It doesn’t hurt to give a good deep watering in autumn and in spring as well.
In subtropical zones, the best watering practice may be to reduce watering a little bit over the cooler parts of the season where growth slows a touch.
Watering Indoor Plants Over Winter
Many well-intentioned gardeners transplant or move their marginally-hardy selections into slightly-warmer locations, like unheated garages or greenhouses. While these insulated spaces protect from the hard freezes experienced by plants left to their own devices outdoors, they are also dry and not open to precipitation. Plants that are moved to sheltered spots should be thoroughly-watered once they are moved, and not allowed to sit dry as the season begins to warm up.
Watering will make or break a houseplant over winter. Most gardeners kills their indoor plants with kindness in the winter months, over-watering and allowing fungal and bacterial pathogens, as well as pesky creatures like fungus gnats to flourish. Keep in mind that with reduced light, houseplants sitting in a window will both grow less and demand less in the way of water.