Evergreens keep our lawns interesting in the winter when their deciduous neighbors have dropped their leaves for the season. For this reason, you probably want to keep your evergreens happy and healthy, and fertilizers are one way to do that!
The most effective evergreen fertilizers are high in nitrogen. This is the mineral most readily absorbed by evergreens as opposed to phosphorous, potassium, or micronutrients. Fertilizers that are high in nitrogen work by providing evergreens with the nutrients they need to complete photosynthesis.
Below, we’ll go over the most effective evergreen fertilizers and give you a little more detail on how they work and when to use them.
Why You Should Fertilize Your Evergreen Tree
Before we get into the best, most effective evergreen fertilizers, let’s answer an obvious question: Does your evergreen need fertilizer?
According to the University Of Minnesota, evergreens need less fertilizer than deciduous trees but still benefit from the occasional nutrient bump.
If your evergreen is showing signs of nutrient distress such as slow growth or abnormally-colored foliage, it may need fertilization to provide missing nutrients.
Applying fertilizer to young trees and shrubs is beneficial to help promote fast growth and development. It’s also beneficial to fertilize evergreens affected by pests or those planted in poor soil conditions. Fertilizers can help the trees bounce back from these stresses more easily.
Newly planted evergreens that aren’t growing very fast do not necessarily need fertilizers. Most of the growth may be happening beneath the soil where the plant is establishing a root system. Nitrogen-high fertilizers are likely to stimulate growth above the soil, not below.
For this reason, it’s not recommended to fertilize evergreens that have just been transplanted. Give them a season or two to establish a good root system before fertilizing.
Another way you can tell if you need to fertilize your evergreen or not is to perform a soil test. This is a little more time-consuming, but it will give you all the details you need about your soil including:
- Nutrient content
- Soil PH – evergreens like their soil to be slightly acidic
- Type of soil – clay, sand, loam, etc.
Knowing this information will put you miles ahead on knowing exactly what your evergreen requires. Knowing the type of soil will also help identify what kind of fertilizer you need.
For example, clay soils tend to promote runoff because it holds water. Using a slow-release fertilizer on clay soils will be more beneficial for your evergreen than using a fast-release, water-soluble fertilizer.
What Time Of The Year Should You Fertilize Your Evergreen Trees?
If you’ve determined that your evergreen needs fertilizer, you want to be careful about when you fertilize it.
Fertilizing your evergreen too late in the season may promote new growth at a time when the tree should be slowing down and hardening off for winter.
Fertilizing your evergreen too early can promote growth before the threat of frost has passed, causing brittle twigs and possible dieback.
So, when is the golden timeframe to fertilize your evergreens?
According to Clemson University, you should apply fertilizer once in early spring and again in early summer. This is when active growth is occurring and nutrients are most likely to be absorbed by your evergreen.
One thing to note is that you should never fertilize your evergreens during a drought.
Evergreens will be stressed from drought and the nutrients will force them to grow when they don’t have the necessary energy or water. This can cause root burn, which can severely stunt your evergreen’s future growth and health.
How Fertilizers Work In The First Place
A lot of people think that fertilizers are ‘plant food.’ This is a common misconception and understandable. After all, fertilizers are nutrients. Isn’t that kind of like food?
In reality, fertilizers simply provide nutrients to your evergreens so that they can make food. evergreens get food from photosynthesis, but for photosynthesis to work, a lot of things have to go right.
Your evergreen has to have green leaves or needles and grow enough to reach the sunlight. It also has to have enough water and carbon.
For all of that to happen, the evergreen needs nutrients.
The most important nutrients for evergreens are nitrogen, potassium, and phosphorous, also known as NPK. But besides that, they also need carbon, hydrogen, oxygen, sulfur, calcium, magnesium, boron, copper, iron, manganese, molybdenum, nickel, zinc, and chlorine!
Fertilizers help to give evergreens all of those nutrients so that they can focus on growing new shoots, new leaves, and flowering, instead of worrying about just surviving with minimal nutrients.
Fertilizers are especially effective for evergreens because these trees continue to photosynthesize all year instead of going dormant in the winter.
You can read more about how evergreens keep growing in the winter here to learn more about that!
Most Effective Fertilizers For Your Evergreens
As we mentioned before, the best fertilizer for evergreens will typically contain high amounts of nitrogen. Phosphorous is rarely needed in evergreen fertilizers, while potassium may or may not be needed depending on the specific area where you live and the soil content.
Other micronutrients like magnesium, calcium, and sulfur are included in some fertilizers but typically are not as important as nitrogen.
Let’s take a look at the most effective fertilizers for your evergreens so you can keep them healthy and green for years to come.
Complete fertilizers are those that have a ratio of the three major nutrients:
These are typically listed in an NPK ratio on the fertilizer container that refers to the ratio of nitrogen, phosphorous, and potassium, respectively. For example, a 16-4-8 complete fertilizer has 16% nitrogen, 4% phosphorous, and 8% potassium.
For evergreens, it’s recommended to use a fertilizer higher in nitrogen such as 16-4-8 or 12-6-6. The reason nitrogen is so important is that it leaches through the soil more quickly than potassium or phosphorus, so it needs to be replenished more often than other nutrients.
The Andersons Store Professional PGF Complete 16-4-8 Fertilizer is a good choice for your evergreen. This is an 18-pound bag and for your evergreen, you want about 3 pounds of nitrogen per 1,000 square feet.
If you can’t stand math, the product we suggested has a table on the back of the bag for easy measurement! That way you’ll know exactly how much to use for your evergreen.
When To Use A Complete Fertilizer
The type of fertilizer you use on your evergreen will depend on a few different things such as what the soil conditions are, what problems your tree/shrub is having, and any results from a soil test.
Complete fertilizers are good to use as a basic fertilizer when you have no real knowledge of what nutrients are in your soil. Complete fertilizers cover all the basics and will be helpful to your evergreen no matter the situation.
Studies like this one reported in PLOS ONE Journal have shown that fertilizers containing the essential NPK nutrients increase the growth and diameter of evergreen trees (fertilizer applied to different forests containing species of Nothofagus betuloides and Nothofagus pumilio in Patagonia.)
The downside to complete fertilizers is they are not geared toward specific situations. If your evergreen is already planted in potassium-rich soil, using a complete fertilizer may overcharge the available potassium nutrients.
While this won’t kill your evergreen, it won’t give it the optimal nutrients it needs and growth may not be as dramatic as you’d like.
Nitrogen-Only Fertilizer (Urea & Ammonium Sulfate)
Urea is used as a fertilizer and has a very high nitrogen content. Urea fertilizers are 46-0-0, meaning it has no potassium or phosphorous in the product. Ammonium fertilizers are usually 21-0-0.
Urea and ammonium fertilizers typically come as granules that can be spread into the soil to give your evergreens a nice nutrient boost.
Nitrogen will promote growth above the soil such as new leaves, needles, and stem growth. Similar to complete fertilizers, you don’t want to apply these to brand-new transplants as you’ll want to give them time to establish roots.
According to the University of Minnesota, urea can quickly be lost to the atmosphere if allowed to sit on the soil surface in warm weather. If you decide to go with a urea fertilizer, be sure to work it into the soil when applying as opposed to simply spreading it on the surface of the soil.
Cesco Solutions, Inc. Store’s Urea Fertilizer 5lb bag contains a ratio of 46-0-0. It comes in the form of granules, which makes for easy spreading. Just remember to work the urea into the soil as it can be absorbed readily into the atmosphere.
For ammonium sulfate, Cesco also makes an Ammonium Sulfate Fertilizer 5lb Bag that’s a ratio of 21-0-0. Ammonium sulfate does not leach into the atmosphere as quickly or degrade as quickly as urea. However, it has a lower nitrogen content.
When To Use A High-Nitrogen Fertilizer
There are pros and cons to using a nitrogen-only fertilizer like urea or ammonium sulfate. Nitrogen is certainly the most important nutrient for evergreens, but it’s not the only nutrient your evergreen needs.
Using a urea or ammonium sulfate fertilizer is a good choice if you know the nutrient contents of your soil.
If you know your soil contains enough potassium and phosphorous, then using a nitrogen-only fertilizer will be the most beneficial to your evergreen.
Adding in extra potassium or phosphorous when your soil already has an abundance can slow growth. So, using a high-nitrogen fertilizer is great if you know your soil is flush with those nutrients.
Slow-release fertilizers are complete fertilizers that are coated with sulfur or some other component to slowly trickle the nutrients into the soil as opposed to releasing them all at once.
Look for a slow-release fertilizer that has similar NPK ratios as complete fertilizers (16-4-8 or 12-6-6). This is the best ratio for evergreen trees, giving them enough nitrogen to promote new above-ground growth.
When using a slow-release fertilizer, you can apply it one time for the entire year, preferably in late spring. These can be supplemented with a fast-release fertilizer if your tree is established but young. For mature evergreens, you don’t need both.
A good slow-release fertilizer would be Schultz Nursery Plus Slow-Release Plant Food. It has an NPK ratio of 12-6-6, which is ideal for evergreens. It also contains other micronutrients that are released slowly into the soil to prevent any type of root burn.
When To Use Slow-Release Fertilizers
So, when should you use slow-release fertilizers as opposed to fast-release or nitrogen-only fertilizers?
Similar to complete fertilizers, slow-release fertilizers are good when you’re not sure what the nutrient content of your soil is. Having all three macronutrients (nitrogen, phosphorous, and potassium) will cover all the bases and give your evergreen enough nutrients to promote new growth.
Specifically, you’ll want to use slow-release fertilizers if your soil is prone to runoff such as in clay soils or on slopes.
According to Clemson University, slow-release fertilizers are also great for young shrubs and trees, giving them a constant supply of nutrients when they need it the most.
Runoff is an important factor when deciding on a fertilizer. According to an article in the Journal of HortTechnology, slow-release fertilizers are less damaging to the environment in terms of entering the water table.
Slow-release fertilizers aren’t a great solution for when your trees are nutrient stressed and need a nutrient boost right away. For those situations, you’ll want a water-soluble fertilizer.
Overall, I really like slow release fertilizers a lot as they’re less likely to overload the tree!
Fast-Release Fertilizers (Water-Soluble)
On the opposite spectrum of slow-release fertilizers are water-soluble fertilizers. These get leached into the soil and are available to your evergreens right away.
Some complete fertilizers are water-soluble, but not all. It will usually say right on the packaging if it’s water-soluble or not.
Miracle-Gro Water Soluble All Purpose Plant Food is a fast-acting fertilizer with an NPK ratio of 24-8-16. This isn’t our perfect evergreen ratio, but it still has high nitrogen, low phosphorous, and mid-range potassium, which is a really good overall combination.
When To Use Fast-Release Fertilizers
As the name suggests, fast-release fertilizers are meant to provide evergreens with nutrients right away. Once the fertilizer enters the soil, your evergreen can immediately absorb them and put them to use.
Fast-release fertilizers are best used on evergreens that are nutrient-stressed. Some of the signs of nutrient stress include:
- Brown or yellow foliage
- Lack of flowers or cones
- Stunted growth
- Lack of any new growth in the spring
In these situations, it’s best to apply a fast-release fertilizer so that your evergreens can quickly fix their nutrient imbalance and continue to grow.
Nothing works quite as good as mother nature to give your evergreen exactly what it needs. Organic fertilizers do just that!
Organic fertilizers for evergreen trees can mean a few different materials:
- Fallen leaves
- Worm castings
The advantage of using an organic fertilizer on your evergreen is that it includes all the macro and micro-nutrients your evergreen will need.
Plus, it avoids the additives and chemicals that come with synthetic fertilizers.
You can use fallen leaves as a replacement for mulch around your evergreens. According to the University of Maryland, this will provide your evergreens with a slow release of nutrients while the leaves break down.
Make sure to chop the leaves up relatively fine so that they break down faster than if the leaves were whole.
Compost is another option, but it’s recommended only to use about a 1-inch layer of compost to fertilize your evergreens.
Worm castings are, well, there’s no good way to put it…it’s worm poo. Worm castings are the result of worms eating through compost, vegetables, leaves, and whatever else they find palatable and passing it through their system.
The result is an extremely rich organic fertilizer that has all kinds of goodies your evergreen will love including the standard NPK, but also magnesium, calcium, phosphates, iron, and a host of other micronutrients.
Unless you are very patient with your worm farm, you’ll want to grab worm casting fertilizers online such as Arcadia Garden Products Worm Nerd Worm Castings. This is a 4-pound bag and is a great organic fertilizer for your evergreen(s).
Guano is another one of those organic fertilizers that aren’t a dinner-table-appropriate conversation. It’s the droppings of seabirds and bats. According to an article in the International Journal of Ecology, ‘guano’ is a Quechua word that translates to ‘fertilizer.’
This organic fertilizer is high in nitrogen and contains many other macro and micro-nutrients that will help your evergreen grow to its full potential each season.
Don’t worry, you don’t have to go cave exploring to find guano fertilizer. Down to Earth’s Organic Bat Guano Fertilizer is a 2-pound bag with an NPK ratio of 7-3-1.
When To Use Organic Fertilizers
Using organic fertilizers is a great choice if you’d rather not deal with chemically-calculated synthetic fertilizers. It’s a more natural solution that’s less likely to harm waterways and the environment.
Because organic fertilizers are considered ‘slow-release,’ they’ll be especially effective for evergreens growing on slopes or in poor soil conditions.
Organic fertilizers have the added benefit of being natural. You don’t have to worry about runoff or any chemicals getting into the water table. You can simply spread the fertilizer and reap the benefits!
The one downside to organic fertilizers is that they don’t contain a concentrated amount of nutrients like synthetic fertilizers.
Fertilizer Spikes And Liquid Fertilizer
Other types of fertilizers available for your evergreens are fertilizer spikes and liquid fertilizer. These aren’t any different than our other fertilizers besides the delivery method.
So far, most of the fertilizers on our list were granules that can be spread around or worked into the soil.
Spikes and liquid forms come in many varieties such as water-soluble or slow-release but have a different delivery methods.
Fertilizer spikes like Miracle-Gro’s Tree & Shrub Plant Food Spikes come in a 15-5-10 NPK ratio. This package comes with 12 spikes and has a guide on the back to let you know how many spikes you should use based on your evergreen’s drip line.
Spikes are more akin to slow-release fertilizers rather than water-soluble fertilizers. They dissolve slowly over time, providing your evergreen with constant nutrients.
Liquid fertilizers are more akin to fast-release fertilizers. They are absorbed into the soil quickly and are available to your evergreens sooner rather than later.
The nice thing about liquid fertilizers is that they come in high nitrogen contents such as 28-0-0, which is great for evergreens.
When To Use Fertilizer Spikes And Liquid Fertilizer
Using spikes or liquid fertilizer is more of a preference than having anything to do with your evergreen’s nutrient or soil situation.
They both come in a variety of different kinds of fertilizers that we discussed above. The only difference is the delivery method.
That’s A Wrap!
Evergreens work overtime in the winter. Unlike most plants that go dormant, evergreens still photosynthesize, keeping their leaves and needles green.
But just because evergreens are hard workers doesn’t mean they won’t benefit from being fertilized here and there.
The best fertilizer for evergreens will be high in nitrogen. This is the most important nutrient for evergreens and can be readily absorbed.
Now, for a quick recap:
The most effective fertilizers for evergreens include:
- Complete fertilizer
- Nitrogen-only fertilizer (Urea & Ammonium Sulfate)
- Slow-release fertilizer
- Water-soluble fertilizers (fast release)
- Organic fertilizers (compost, worm casting, leaves, guano)
- Fertilizer spikes
- Liquid fertilizer
These fertilizers should be used depending on your evergreen’s specific situation. Knowing the nutrient content and type of soil where your evergreen is growing is a huge advantage.
Best of luck on your tree journey!
Chastain, R. A., Currie, W. S., & Townsend, P. A. (2006, August). Carbon sequestration and nutrient cycling implications of the evergreen understory layer in Appalachian forests. Forest Ecology and Management, 231(1-3), 63-77.
Promis, A., & Allen, R. B. (2017, November 30). Tree seedlings respond to both light and soil nutrients in a Patagonian evergreen-deciduous forest. Plus One, 12(11).
Scagel, C. F., Bi, G., Fuchigami, L. H., & Regan, R. P. (2007, October). Seasonal Variation in Growth, Nitrogen Uptake and Allocation by Container-grown Evergreen and Deciduous Rhododendron Cultivars. HortScience, 42(6), 10.
Souraya Sakoui, Reda Derdak, Boutaina Addoum, Aurelio Serrano-Delgado, Abdelaziz Soukri, Bouchra El Khalfi, “The Life Hidden Inside Caves: Ecological and Economic Importance of Bat Guano”, International Journal of Ecology, vol. 2020, Article ID 9872532, 7 pages, 2020.
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