Winter Watering of Conifers
January 6, 2026
Conifers, are fantastically smart trees!
We're talking about firs, junipers, pines, and spruces; trees that reproduce with cone seeds. While conifers are evergreens, not all evergreens are conifers. Some evergreens are broadleaf flowering trees, and some conifers are deciduous trees that shed their leaves annually. So, the better way to talk about them is to call them conifers, short for coniferous.
Conifers have been on Earth for over 300 million years. In comparison to flowering broadleaf trees that have only been around for about 140 million years, conifers are elder trees! And with that experience comes the wisdom of conservation. These trees have a phenomenal ability to conserve energy, and that means preventing water loss.
Conifers have highly controlled growth habits written into their DNA. When surrounding resources are limited, conifers can drastically reduce their new growth. Less leaves, means less demand. Another trait is a waxy cuticle over each needle that protects from wind and heat - factors that increase evapotranspiration (water loss).
Perhaps the neatest trait, is inducing two periods of dormancy a year - summer and winter. Many processes come into play, but the main one is a closing of stomata to inhibit water loss through the needles.
Periods of rest are how conifers conserve water and energy for growth. Summer dormancy is initiated with temps rising above 85°. Winter dormancy is brought on by consistent sub-freezing temperatures and frozen ground. These periods are key to conifer survival.
Here's the catch! These cues for winter dormancy simply aren't happening in our yards anymore. Winters are warming and snows are depleting. This means our conifers are using more water and working longer each year than before. This equates to stress!
Anytime it's between 25° and 85°, and the ground is thawed; we can assume that our evergreens are pulling water and working. Your conifers are likely working right now.
As tree growers, our most important job is to inspect the soil for moisture and to apply water when dry. The new normal for conifers is that watering could be necessary throughout winter.
I refer to soil moisture as being between three ranges: saturated, moist, and dry. Checking soil moisture can't be easier and this method applies to all trees!
All you'll need is a screwdriver. We need to be sure we're checking soil moisture within the critical root zones of our trees. The critical root zone is the area of roots, measured in a radius from the trunk, that are critical to sustaining current biomass.
Again, we can keep this very simple. For large conifers, we'll check a couple places inside a twenty foot radius. For medium conifers, let's check a couple places inside a ten foot radius. For small trees, we'll check within a five foot radius. And for conifers that have been planted in the last few years, let's check once within the planting area and once just outside of the planting area.
We're aiming for around six inches deep. Pull the screwdriver out and look at it.
Is soil stuck to the screwdriver like mud? This means your soil is saturated.
Is there some soil on it, but easy to wipe off? Your soil is moist.
For either of these two results, you don't need to water. Your soil is adequately moist. Applying more water at this time would actually be stressful to any tree or shrub.
Is the screwdriver still shiny and clean, maybe just a bit of dust? Your soil is dry and should be watered.
It's really that simple!
Some of you are using soil moisture meters. That's great! I've recommended these for years. The inexpensive ones you find at your local garden center work just fine. In compacted soils you'll want to make your meter hole with a screwdriver first, as the meter probe isn't designed for compact soils and can be broken easily.
It feels cool using the meter; watching the needle move through measurements feels precise. I still use mine. But after years of doing this, I've learned that the screwdriver tells all you really need to know. Meters occasionally give false readings and can be tough to bend down and read in some landscape settings. Mud on a screwdriver never lies!
We're aiming for a six inch depth because the majority of fibrous roots in urban or developed soils are concentrated between four and six inches. Fibrous or tertiary roots are the tiny string and hair sized roots responsible for pulling water into the plant. There are roots above and below this, but the majority are here, just below turf grass roots.
Another way to test soil moisture is to roll the soil into a ball and toss it around. If the soil sticks together and doesn't break when you toss it; your soil is saturated. If it sticks together at first, but starts to fall apart after a few tosses; your soil is moist. If you can't get it to roll into a ball, your soil is dry and needs to be watered.
Everything I've said here about checking soil moisture and watering when dry, is true for all of your woody plants: trees and shrubs alike. It's true whether they're inside or outside. Inside plants are in different soil mediums and volumes, so root depths will vary. But the general rule of applying water when soil is dry, stands true.
So, why is that so important?
I'm glad I pretended you asked. Woody plants are about 80% water by mass. They're basically just organisms that have gotten really good at trapping water between thin layers of woody tissues. We're fooled by all the cellulose and lignin packed around all the water, making up trunk, stems, leaves, flowers, seeds, fruits. The entire mechanism, all of its life processes require water. To be most accurate is to say that when water enters the plant, it's actually not water anymore...or not, just water.
The water is now a mixture of elements being delivered to the plant. Some of these elements are considered essential, most aren't. In a tree, we might find upwards of one hundred different elements suspended in a molecule of water. Around 18, are considered essential, including the hydrogen and oxygen making up the molecule of water.
We can't force water to absorb nutrients in the soil. We can't force the processes of diffusion and osmosis that get water to the roots and into the roots. We can't pull the water up and into the plant, or distribute it to all the parts. And we certainly can't tell each part of the tree what exact concoction of elements to pull and use where and for what processes. The tree, along with the dynamics of its environment, is responsible for all of these processes.
Our job, is simply to ensure that our trees have the water to work with!
Evergreens specifically, are having a tougher time getting the water they need.
Conifers, are fantastically smart trees!
We're talking about firs, junipers, pines, and spruces; trees that reproduce with cone seeds. While conifers are evergreens, not all evergreens are conifers. Some evergreens are broadleaf flowering trees, and some conifers are deciduous trees that shed their leaves annually. So, the better way to talk about them is to call them conifers, short for coniferous.
Conifers have been on Earth for over 300 million years. In comparison to flowering broadleaf trees that have only been around for about 140 million years, conifers are elder trees! And with that experience comes the wisdom of conservation. These trees have a phenomenal ability to conserve energy, and that means preventing water loss.
Conifers have highly controlled growth habits written into their DNA. When surrounding resources are limited, conifers can drastically reduce their new growth. Less leaves, means less demand. Another trait is a waxy cuticle over each needle that protects from wind and heat - factors that increase evapotranspiration (water loss).
Perhaps the neatest trait, is inducing two periods of dormancy a year - summer and winter. Many processes come into play, but the main one is a closing of stomata to inhibit water loss through the needles.
Periods of rest are how conifers conserve water and energy for growth. Summer dormancy is initiated with temps rising above 85°. Winter dormancy is brought on by consistent sub-freezing temperatures and frozen ground. These periods are key to conifer survival.
Here's the catch! These cues for winter dormancy simply aren't happening in our yards anymore. Winters are warming and snows are depleting. This means our conifers are using more water and working longer each year than before. This equates to stress!
Anytime it's between 25° and 85°, and the ground is thawed; we can assume that our evergreens are pulling water and working. Your conifers are likely working right now.
As tree growers, our most important job is to inspect the soil for moisture and to apply water when dry. The new normal for conifers is that watering could be necessary throughout winter.
I refer to soil moisture as being between three ranges: saturated, moist, and dry. Checking soil moisture can't be easier and this method applies to all trees!
All you'll need is a screwdriver. We need to be sure we're checking soil moisture within the critical root zones of our trees. The critical root zone is the area of roots, measured in a radius from the trunk, that are critical to sustaining current biomass.
Again, we can keep this very simple. For large conifers, we'll check a couple places inside a twenty foot radius. For medium conifers, let's check a couple places inside a ten foot radius. For small trees, we'll check within a five foot radius. And for conifers that have been planted in the last few years, let's check once within the planting area and once just outside of the planting area.
We're aiming for around six inches deep. Pull the screwdriver out and look at it.
Is soil stuck to the screwdriver like mud? This means your soil is saturated.
Is there some soil on it, but easy to wipe off? Your soil is moist.
For either of these two results, you don't need to water. Your soil is adequately moist. Applying more water at this time would actually be stressful to any tree or shrub.
Is the screwdriver still shiny and clean, maybe just a bit of dust? Your soil is dry and should be watered.
It's really that simple!
Some of you are using soil moisture meters. That's great! I've recommended these for years. The inexpensive ones you find at your local garden center work just fine. In compacted soils you'll want to make your meter hole with a screwdriver first, as the meter probe isn't designed for compact soils and can be broken easily.
It feels cool using the meter; watching the needle move through measurements feels precise. I still use mine. But after years of doing this, I've learned that the screwdriver tells all you really need to know. Meters occasionally give false readings and can be tough to bend down and read in some landscape settings. Mud on a screwdriver never lies!
We're aiming for a six inch depth because the majority of fibrous roots in urban or developed soils are concentrated between four and six inches. Fibrous or tertiary roots are the tiny string and hair sized roots responsible for pulling water into the plant. There are roots above and below this, but the majority are here, just below turf grass roots.
Another way to test soil moisture is to roll the soil into a ball and toss it around. If the soil sticks together and doesn't break when you toss it; your soil is saturated. If it sticks together at first, but starts to fall apart after a few tosses; your soil is moist. If you can't get it to roll into a ball, your soil is dry and needs to be watered.
Everything I've said here about checking soil moisture and watering when dry, is true for all of your woody plants: trees and shrubs alike. It's true whether they're inside or outside. Inside plants are in different soil mediums and volumes, so root depths will vary. But the general rule of applying water when soil is dry, stands true.
So, why is that so important?
I'm glad I pretended you asked. Woody plants are about 80% water by mass. They're basically just organisms that have gotten really good at trapping water between thin layers of woody tissues. We're fooled by all the cellulose and lignin packed around all the water, making up trunk, stems, leaves, flowers, seeds, fruits. The entire mechanism, all of its life processes require water. To be most accurate is to say that when water enters the plant, it's actually not water anymore...or not, just water.
The water is now a mixture of elements being delivered to the plant. Some of these elements are considered essential, most aren't. In a tree, we might find upwards of one hundred different elements suspended in a molecule of water. Around 18, are considered essential, including the hydrogen and oxygen making up the molecule of water.
We can't force water to absorb nutrients in the soil. We can't force the processes of diffusion and osmosis that get water to the roots and into the roots. We can't pull the water up and into the plant, or distribute it to all the parts. And we certainly can't tell each part of the tree what exact concoction of elements to pull and use where and for what processes. The tree, along with the dynamics of its environment, is responsible for all of these processes.
Our job, is simply to ensure that our trees have the water to work with!
Evergreens specifically, are having a tougher time getting the water they need.
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