Thank you for your question about watering needs for spruce trees.  I have found several sources of info and I have included the website for your information.




https://www.hunker.com/12003464/how-much-should-i-water-my-spruce-trees
Watering spruce trees is tricky. Over watering causes branches to turn brown, starting at the bottom. If the soil is heavy, such as clay, ensure that trees do not stand in water. If the roots are choked of oxygen, fungal disease attacks the tree, or it creates a shallow root system, allowing the tree to easily topple. Standing water leaves behind mineral build-up affecting the soil quality. Watering is crucial the first two days after a tree is planted. Soak the soil once a week when it is not raining. Place a hose trickling water by the tree's base and allow it to run for several hours or overnight for large trees. Extremely large trees should only be watered once a month, unless drought conditions are occurring.

https://treejourney.com/tips-for-watering-your-spruce-tree-and-when-to-do-it/

Young and newly planted spruce trees require more water than established ones. Drought-stressed spruce trees should be watered thoroughly during all seasons, especially when needles are browning. For every inch of trunk diameter, your spruce tree should get at least a gallon of water.

Spruce trees that are water-stressed are more likely to develop disease or fall prey to pests. Below, we’ll go over a few tips for how often you should be watering your spruce tree!

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When Your Spruce Tree Needs To Be Watered

If your spruce tree is looking healthy and growing just fine, does it need to be watered or can you leave it alone?

Spruce trees don’t always need to be watered. However, under certain conditions, you should take the time to water your spruce tree to prevent drought stress.

Some examples of when you need to water your spruce tree include:

• When it’s young
• When it’s first transplanted
• During dry periods or droughts

According to the University of Nebraska, signs of drought stress may not show immediately. If your spruce is water-stressed in July, you may not see symptoms until late August or September.

Looking for signs of drought stress is essential, but it’s even MORE important to prevent water stress before it happens. This means paying attention to the weather and understanding when your spruce needs watering.

9 Tips For Watering Your Spruce Tree

Water is essential for spruce tree health. Too little or too much and your spruce tree is going to start shedding needles and looking droopy.

Nobody wants a spruce tree that turns from brilliant green to a drab brown! Let’s check out a few tips for watering your spruce tree so you can keep it healthy, green, and thriving.

1. Check For Soil Dryness

Just because it sprinkled rain a few days ago doesn’t mean your spruce tree has had enough water. Many of the roots of a spruce tree go deep into the soil, meaning small amounts of rain aren’t going to cut it.

Check the soil around your spruce tree to get a more accurate idea of whether or not it needs to be watered.

In general, if you place your finger in the soil and it’s dry, your spruce tree needs watering. If you’re willing to go a little more in-depth, you should check the top 6-9 inches of soil for dryness to get a more accurate picture.

It’s important to note that if 1 inch or more of rain is predicted to occur that week, even if the soil is dry, you do not need to water your spruce. Overwatering can promote the growth of fungus, so if heavy rain is in the forecast, hold off on watering.

2. Know The Soil Under Your Spruce Tree

Spruce trees can thrive in a variety of soil types, from sand to clay. The type of soil where your spruce tree is planted is an important factor when considering how much and how often to water.

There are three basic types of soil texture:

• Sand: Sand is the most porous soil type. The particles are very large and therefore allow water to flow freely through.
  
• Clay: Clay has the smallest particles and holds water longer than sand.
  
• Silt: Silt falls somewhere in between sand and clay.

Knowing what type of soil you have under your spruce tree can give you an idea of how often you should water.

Spruce trees planted in soils with a higher sand content will need to be watered more often. The opposite is true for clay. Most of the time, the soil will be some combination of these three textures. Very rarely is soil completely clay or completely sand.

3. Newly Planted Spruce Trees Should Be Watered

It’s very exciting to plant a new tree in the yard. You have to pick out the perfect spot and envision what it will be like when the tree is fully grown.
Transplanting a spruce tree from a container to the yard can be tricky. One thing that is recommended is to thoroughly soak the soil once your tree is planted. 
According to the University of Minnesota, you can use the diameter of the tree trunk to determine how much water your spruce tree should need at the time of transplant. At a minimum, for every 1 inch of trunk diameter, the tree will need 1 gallon of water.
After your spruce tree is transplanted, there is going to be a period where the tree is adjusting to its new home and getting all settled in. 
At this time, the roots will begin reaching out into the soil. What you don’t want is to only water the top few inches of soil. This is going to teach the roots that they should not dive deep into the soil for water, but stay close to the surface.
You’ll want to water the transplant deeply to train the roots to establish deep within the soil. This will promote a stronger tree that can better withstand high winds and storms.

4. Water Spruce Trees Deeply For Better Root Growth

Spruce trees are particularly sensitive to drought conditions. One of the reasons is because of the way their roots respond to water stress.

According to an article in the Journal of Forest Ecology and Management, drought causes an increase in fine root mortality. In other words, the small roots that are reaching out for new resources die off quickly during drought conditions.

Fine roots are responsible for absorbing both nutrients and water in the soil. When these roots die back from drought, they can no longer deliver water and nutrients to the leaves (needles) of the spruce tree.

One way to prevent drought stress is to water your spruce tree deeply as opposed to just a surface sprinkle. Watering your lawn isn’t enough to keep a spruce tree watered.

It’s recommended to water so that the soil is wet down to at least 9 inches. Providing water deeper into the soil will help train spruce tree roots to establish farther into the soil as opposed to shallower surface roots.

5. Use Mulch To Retain Moisture

Mulch has so many benefits around the yard. Not only does it make your yard look neat and trim, but it also helps keep moisture in the soil longer and protects your tree from the cold in winter.

It’s basically just a big security blanket for your spruce tree!

There are a few things to note when using mulch around your spruce tree:

• Remove all grass first: Spruce trees compete with grass for surface water, and grass usually wins because the roots are so fibrous. Make sure to remove all grass before you put your mulch down.
  
• Choose the right mulch: Make sure you purchase quality mulch so that you’re not running into problems with insect pests that may be hiding in lower-quality mulch.
  
• Give the trunk breathing room: Keep the mulch at least a foot away from the tree trunk to ensure the trunk has room to grow and is not smothered.
  
• Avoid over-mulching: You can add 2-3 inches of mulch around the tree, but it’s not recommended to go any deeper as this can promote weeds, smother roots, and give mice and rats a nice home to live in while they gnaw on your spruce’s roots!

Depending on what kind of spruce tree you have, you may not be able to use mulch. For example, blue spruce trees often have branches that reach the ground.

It’s not recommended to trim these branches, so you’ll have to employ some of our other tips to keep your spruce tree well-watered.

6. Use A Slow Trickle Of Water

When we think of watering deeply, you may be thinking of using a hose or a pail to pour tons of water at the base of your spruce tree.  
This will get the job done, but it’s not as efficient as using a slow trickle of water over a longer period. Instead of giving your spruce tree a ton of water all at once, consider using your hose or an irrigation system to let a slow trickle come out over the course of several hours.

To use a slow trickle of water you can simply set your hose out near your spruce tree and set the nozzle to only drip water instead of a constant stream.

The best time to use your hose to water your spruce tree is in the evening. Let it trickle throughout the night and turn it off in the morning. This will help completely saturate the soil but the slow trickle means the soil will not be soaking wet.

Alternatively, you can hook up an irrigation system using something like Flantor Garden Irrigation System.

This kit comes with tubing, nozzles, and spikes that you can hook up to your water supply, making it easy to drip-feed your spruce as opposed to lugging out the garden hose every week.

Just remember, if there’s rain in the forecast that week, it’s better not to water your spruce tree. Overwatering can create just as many problems as underwatering.

7. Water Beyond Your Spruce Tree’s Dripline

How much water you give your spruce tree is an important aspect of keeping your spruce tree healthy. Where you water may be just as important!

When you bust out the garden hose or your irrigation system, you can’t just spray all willy-nilly around your spruce tree.

Spraying too close to the trunk of your spruce tree can promote the growth of fungus. Try to avoid too much water in a 12-inch circle around the trunk of the spruce tree.

You can drip feed or use an irrigation system beyond this 12 inches. Most of the time when people water their trees they only water to the drip line.

The dripline is the outermost region of the spread of the tree. So when it rains, figure out how far out the rain drips from your tree’s leaves and branches. This is the dripline, which goes in a circle around the entire tree.

The problem with only watering up to the dripline is that the tree’s roots can grow far beyond that point. Make sure to water your spruce tree beyond its dripline to give far-reaching roots enough water.

The healthier your spruce tree is, the less chance that it will fall to pests or tree afflictions.

8. Remove Grass Under Your Spruce Tree

We mentioned grass a little bit earlier when we talked about mulching around your spruce tree. It’s certainly a good idea to remove grass before placing down mulch.

It’s also a good idea to remove grass entirely from under your spruce tree, whether you mulch it or not. Grass should be removed under your spruce tree for a few different reasons:

• Competition: Grass roots are very shallow and will compete with deeper spruce roots for water and nutrients. Unfortunately, because shallow roots get the first shot at rainwater, there may not be enough left for deeper spruce roots.
  
• Pests: some pests like rabbits, gophers, squirrels, and mice find haven in tall grass. These animals are also known to damage trees by chewing bark, twigs, and even root systems of spruce trees.
  
• Reduce mowing damage: If you have grass under your spruce tree, chances are you have to mow it or use a weed trimmer. Using this type of equipment close to your spruce tree can damage the tree and any shallow roots.  
  
  Remove Grass Under Your Spruce Tree
  We mentioned grass a little bit earlier when we talked about mulching around your spruce tree. It’s certainly a good idea to remove grass before placing down mulch.
  It’s also a good idea to remove grass entirely from under your spruce tree, whether you mulch it or not. Grass should be removed under your spruce tree for a few different reasons:
  
  • Competition: Grass roots are very shallow and will compete with deeper spruce roots for water and nutrients. Unfortunately, because shallow roots get the first shot at rainwater, there may not be enough left for deeper spruce roots.
    
  • Pests: some pests like rabbits, gophers, squirrels, and mice find haven in tall grass. These animals are also known to damage trees by chewing bark, twigs, and even root systems of spruce trees.
    
  • Reduce mowing damage: If you have grass under your spruce tree, chances are you have to mow it or use a weed trimmer. Using this type of equipment close to your spruce tree can damage the tree and any shallow roots.
    
  
  
  
  
  9. Water Your Spruce Tree At The Right Time
  
  
  Watering is extremely important to the health of your spruce tree. However, if you water at the wrong time, it could cause your spruce tree to expend energy it doesn’t have to process the water.
  Here’s when you should water your spruce tree:
  
  • Directly after planting it
  • When the soil feels dry to the touch (if there’s no rain in the forecast)
  • During a drought
  • If there’s been less than an inch of precipitation over a 7-day period
  • If needles begin turning brown
  • In the fall, just after the leaves start to change and before the ground freezes

This last response was written by an extension expert.
https://ask2.extension.org/scp/tickets.php?id=8334
Most varieties of spruce trees have a medium to high need for moisture. Spruce trees do not tolerate drought conditions so proper watering is imperative to their health.

You are fairly accurate in determining how much water each tree requires. The measurement of the trunk diameter (circumference divided by pi 3.14) taken at knee high x 10 gallons of water per inch diameter.

For medium size trees with a trunk diameter of 8"-15", the best methods of watering are: a soaker hose coiled several times under the dripline of the tree, a garden hose with a soft spray attachment, or a soil needle. It is important to know the output of any watering method you are using. Soaker hoses, for example, are rated at ## gallon per foot, per hour @ ##psi. You should be able to calculate the water output based on the length of hose under each tree.

In the case of evergreens, water should be applied 3’-5’ beyond the dripline around tree. Water does not need to be applied to the area next to the base of the tree, so the soaker hose can begin coiling further out and extend to 3'-5' beyond the dripline.

Mulch will help conserve soil moisture. Mulch should be about 4" deep, making sure that it is 6" away from the trunk of the tree. Mulching up against the trunk will cause bark decay and lead to pests and disease.

Tree size, exposure, soil type and weather conditions should regulate how frequently watering should occur. With a trowel, dig down into the soil near the planting area and squeeze some of the soil into a ball. If the soil feels dry and crumbles in your hand, it is time to water. Soil that feels moist and holds together when squeezed doesn't need water.

For slope modifications, east- and north-facing slopes are cooler and retain moisture longer. For west- and south-facing slopes, an extra line of soaker hose may be appropriate, but again, this may be determined based on how moist or dry the soil feels compared to the other irrigated areas.

Finally, watering trees in the winter when there is little to no moisture is crucial. Tree roots continue to grow throughout the winter and need moisture to survive. Evergreens lose water continually through the needles so keep these trees watered. Generally, water one to two times per month October through March on a warm day when temperatures are above 40 degrees.

I hope this is helpful.  Best of luck with your spruces

















https://ask2.extension.org/kb/faq.php?id=284845

This is outstanding information, thank you very much!

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