Should you water trees and shrubs in the winter? It depends. There are times you should water and there are others when you shouldn’t.
No, DirtFarmerJay isn’t being “wishy-washy.” Watering (or not) really does depend on a few factors. Once you know these factors, you can know whether it’s a good idea to water or not.
The FIRST thing you need to know is that root development is a YEAR-ROUND activity, even in climes where it freezes during the winter months. If the ground is not frozen, many trees and shrubs continue root activity that is critical to the overall growth and health of the plant. While the top is dormant, the root system continues to grow main structures (for anchorage and more area for moisture and nutrient acquisition), as well as root hair development. These root hairs exponentially increase root surface area needed for ongoing growth and longevity.
NEXT, you need to know that temperature greatly affects the need for water. And, it’s soil, not air, temperature we’re talking about. There is always a difference between the two. Soil temps generally lag in air temperature trends. That is, if the temperature is dropping over several weeks, the soil will take longer to reach those lower temps. The inverse is true as well. As the air warms up in the spring, the soil will take time to get to favorable planting and growing temps.
To measure soil temps, you can buy an inexpensive soil thermometer. Here’s a sample of an inexpensive (around $8 at the time of filming) soil thermometer that is available at Tractor Supply Company locations in the U.S.:
Practically speaking, if the soil is 40°F/4-5°C or more, and the soil is not moist to a depth of 12”/30cm, then watering can be a benefit and you should consider doing it. If the soil is below that temperature, don’t. It won’t do much if any, good. Also, if there’s good snow cover or thick mulch at the base of the tree, or there have been recent rains, you can delay watering.
THEN, you need to know what kinds of trees are at the greatest risk for not having enough wintertime water. No matter what variety of planting, recent and new transplants are highly susceptible to drought. That’s because they haven’t had sufficient time to develop their root system. So, they need supplemental water. Come springtime, you’ll be glad you made the effort.
Evergreens are at risk for desiccation. This is when the root system cannot harvest enough moisture and nutrients to sustain the metabolism of the tree. Because true evergreens are active both above and below the soil level, more water is needed. Add to this that many evergreen plantings do not mimic nature (being planted in stands with lots of needle covering on the ground), and you may have trouble. Stands of trees act as windbreaks, provide shading, and retain moisture better (both in-ground and tree surface). Place these trees in solitary plantings, with wind exposure and no or very little ground cover, and you’ve put your tree in a very unpleasant situation usually resulting in desiccation. When that happens, the most exposed portion of the tree or to ongoing southern sunlight starts to die back, beginning at the tips of the branches and working back to the trunk. You know this has happened come warm weather and those brown areas don’t rejuvenate.
Even for deciduous trees that have dropped all their leaves, if the weather is warm, soil temps are up, and there hasn’t been much moisture lately, a drink of water can go a long way in protecting your yardscape investment and getting beautiful results in later when the warm weather returns. Cold air cannot hold much moisture, so humidity will be quite low. So it’s up to you to make up the difference when warranted.
The water or not to water, that is the question. And now, you know the answer and you can JUST DO IT YOURSELF!
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Hey, Dirt Farmer Jay here from DirtFarmerJay.com.
Well, it's winter time.
Should I be watering my trees and shrubs?
Well, yes and no.
What gives?
Stay tuned and I'll clear up the mystery for you.
Hey, Dirt Farmer Jay here from DirtFarmerJay.com.
It is flipping cold out here.
It's a little breezy.
It's winter.
Should I be watering my trees?
Well, yes and no.
So which is it?
Am I just being wishy-washy?
No, actually, there's some factors you need to know
to make a decision of whether or not
you need to water your trees and shrubs.
And there are certain kinds of trees and shrubs
that can benefit.
And there's a couple conditions you gotta know about.
The first thing you gotta think about is temperature.
So you can see here,
the temperature here today is right at freezing.
But the soil temperature is what we're really talking about
when it comes to watering or not.
And you can see right here,
I took a little soil thermometer, placed it in the ground.
And what do you know?
It's right at 40 degrees.
And that's something you need to know
about soil temperature and air temperature.
Whatever trend the temperature is going,
let's suppose it's now cooling down for the season.
It's fall.
Well, those nighttime temperatures,
the air temperatures can drop very quickly,
but the soil temperature is gonna lag behind
and stay warmer for a lot longer.
Inversely, the same is true in the spring.
The air temperature gets really nice.
You're out enjoying things
and you're gonna go plant your tomatoes in really cold soil
because that soil has not warmed up yet.
It's lagging in temperature.
And that's all to say right now,
you've got to know the soil temperature
to know whether or not even to consider watering.
So why do you need to water trees and shrubs
in the winter anyway?
I mean, look at them.
They look pretty sparse,
especially if they're deciduous.
There's nothing happening here.
Well, don't be fooled.
You're looking at the dormant part of the tree,
the part of it that's visible,
but there's a lot going on below the soil line.
Here's what's happening.
You think about this.
Roots continue to develop until the ground is frozen
in many varieties and cultivars of trees and shrubs
for a couple of reasons.
Number one, more anchorage is being accomplished
during that time.
Main root structures are forming
to make the tree more stable.
It's acquiring new territory, so to speak.
It is broadening the area
that it can access moisture and nutrients.
So that's all happening
while it's not actively interacting with the top growth
and the sugar transfer between the leaves and all that
when everything's green.
The other thing that's happening,
and this is very key, many people don't know about this,
but now you will,
is there's a lot of root hair development
that's going on during this time.
Root hair?
Yeah, it's a real thing.
This is those real fine little fibers you see.
Sometimes they're very matted.
And what this is doing, what the tree is doing,
is exponentially increasing the surface area of root
so that it has much more access to moisture
and accompanying nutrients.
So all that's gotta happen during the winter,
and that's going on while we're warm in our house
or in our shop or whatever.
So that's why you gotta keep water there.
Now let's talk about a couple of categories of plantings
that are really at risk for winter damage
from lack of moisture.
Well, the first one's not a cultivar.
It's not a type.
It's not a category other than this.
Those plantings that were planted recently
in the previous growing season or just before fall came on,
I like to do transplanting during the fall
to allow winter development of the root system,
but they don't have a full root system in place yet
since they were transplanted,
and many times root pruned
before they were put in the transplant pots and all that.
So you've gotta help them along.
They can't do all this work themselves if it's really dry,
and as you know, winter, cold air really has a hard time.
It cannot hold much moisture.
You know that from the static electricity in your house
and dry skin and all that.
So it's not getting moisture from the air,
and if there's not moisture in the ground
because winds are taking it off
or there's not much moisture because of snow or rain
or mulch cover, all that,
then it's up to you to take care of that investment,
and you'll be really glad you did
when it comes around to that warm season again
and things really take off
because of that root development.
So the first thing is just transplant.
Take good care of them.
Give them lots of mulch too.
Mulching can never go wrong.
Well, the second category that is really at risk
are evergreens, and if you think about it,
it's really simple.
Evergreens are much more active
for a longer time in the season.
They're still doing a lot of work above ground.
Things are active.
Sure, they go through different phases
and when new needles are generated,
but there's a metabolism that is actively happening,
and if you think about the way evergreens grow in nature,
a lot of times that's not how we treat them
in our yardscape plantings.
So in nature, you see them in stands,
in clusters, in groups.
Well, you know the economics of buying evergreens,
at least out in the Mountain West
where we are in the United States.
I can't afford to buy a whole stand of them.
I'd rather buy a table saw
or maybe a new truck or something.
You know what I'm saying?
They can get very expensive quickly,
and I guess that depends on where your priorities are,
but my point being that you generally see them
in smaller areas or in solitary plantings.
Well, that's really hard on the tree,
and here's why.
In cluster plantings, there's wind protection,
there's shading that's happened,
rain that comes is held longer,
and the surface of the tree is well in the ground below it.
Snow is trapped and feeds into the soil
slower over a period of time.
Also, think about this.
When you've walked in the forest the last time
where there are evergreens,
what's all over the ground?
All those needles, right?
Well, there's a lot of reasons the tree's doing that,
but one of the things it does accomplish
is soil conditioning and moisture and nutrient retention.
But many of our plantings,
they're kind of out there bare by themselves,
and we put these trees into a stress situation.
Now, when this happens and the tree is getting
direct sunlight on these warm winter days
where it's really still outside, the sun comes out,
or when you have prevailing winds that hit the trees,
you can run into what's called desiccation.
And desiccation is when the tree dries out
and the root system cannot supply
the needed moisture and nutrients to the top of the tree.
And what you see is die back in the tree,
starting at the tips of the needles and branches,
and then working back to the trunk and then down.
And you see here in this picture that is courtesy
or was supplied by Colorado State University,
you can see this tree,
even though it's in the prime growing time
in this lush green area, it's kind of solitary.
It's by itself.
And the previous winter, it suffered from desiccation.
There was a lot of wind around that and sunlight,
and you can see the die back,
and it didn't rejuvenate
when it's that beautiful growing time.
That's desiccation.
So you gotta watch that.
And that means additional waterings
and covering the ground when you can with mulch
or other organic materials to mimic the growing conditions
as much as possible for your evergreen trees.
And even for your deciduous trees
and ones that drop their leaves
and they're sitting there looking like they're dead asleep,
you know, if it's been dry for a while,
it's been really windy,
you haven't gotten moisture coming at you
and it's not forecasted,
what's the harm in giving them a little bit of a drink?
They'll thank you for it
and it's a protectment of your investment.
Hey, if you've got any insights on all of this,
we'd love to hear it.
Go to the comments below.
And oh, by the way, I forgot to mention this.
There's also a link down below
where you can get a little temperature
or a little soil thermometer yourself.
And they're very inexpensive,
but you can do that
rather than don't take out your candy thermometer,
your kitchen partner will be upset with you
and it won't work anyway.
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Until the next time, this is Dirt Farmer Jay
going to get the watering hose.
