Arborvitae Fertilizer: Best Products and How to Use Them
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Arborvitae are beautiful, low-maintenance trees that fill in empty spaces and make lovely green screens thanks to their conical shape and dense, vibrant green foliage. But low maintenance doesn’t mean no maintenance, and in my experience, you need to fertilize properly if you want to keep these trees full and healthy.
The best fertilizer for arborvitae is a slow-release formula high in nitrogen for a vibrant green color along with lower amounts of phosphorous and potassium. Granular, spike or liquid formulations all work well, but granules and spikes tend to the be easiest and most effective methods. Arborvitae usually does best with 1-2 applications of fertilizer in the spring and fall.
There are many fertilizer options out there, but not all of them are suitable for arborvitae. So in this article I’ll go over the why, when, and how to fertilize, as well as my recommendations for the top arborvitae fertilizers.
Let’s get started!
Nutrient Requirements for Arborvitae
Like all plants, arborvitae needs certain macro and micro nutrients to grow, stay healthy and look their best.
There are three main macronutrients or “Big Three”: nitrogen, phosphorus, and potassium.
- Nitrogen powers green leafy growth.
- Phosphorus enables the plant to produce new cells and stem/foliage growth.
- Potassium promotes the movement of nutrients and water through the plant and activates enzyme action for energy production.
These three nutrients are indicated in a number form (N-P-K) on every bag of fertilizer, where the first number is nitrogen, the second is phosphorus and the third is potassium.
Arborvitae’s main draw is their dense green foliage. To keep that foliage healthy and vibrant, you’ll need a fertilizer with plenty of nitrogen. These trees are also somewhat susceptible to fungal infections, so phosphorus and potassium will help keep them strong and resist disease.
Knowing your local soil profile will also help you choose the right fertilizer. For example, if you know your soil generally has plenty of phosphorus but tends to be low in potassium, then a good NPK number is 16-4-8. If your soil has lots of nutrients and organic matter, then 11-3-4 will work well. If your soil is generally thin and poor, use 11-7-7.
In general, it’s not a good idea to use a balanced formula (where the NPK values are the same) on arborvitae. An example would be a 13-13-13 fertilizer formulation– it’s great for flowering and fruiting plants but is just too rich for greenery like arborvitae. Using a high-nutrient formulation like this usually leads to root burn and problems like foliage browning and drooping.
Most fertilizers contain these three macronutrients, and some contain only these. Others might also include micronutrients, which arborvitae need in smaller amounts, including:
Types of Arborvitae Fertilizers
Arborvitae fertilizer, and tree fertilizers in general, come in three different application types
Let’s do a quick overview of each one and how one might be better than another depending on the site and situation.
Granular fertilizers are, as the name implies, solid fertilizer solutions compressed into small granules about the size of a BB pellet. They are very shelf-stable and tend to be the most affordable type of fertilizer per unit, especially if buying large amounts of fertilizer for many arborvitae trees.
They do need to be in contact with water to dissolve, so should be placed carefully on the soil over the root ball and beneath a drip emitter or sprinkler. Just be aware that pets have been known to find granular fertilizer a tasty but potentially hazardous treat, and small children should also be kept away from freshly-applied fertilizer.
Who It’s Best For:
Granular formulas are great if you’re on a budget for your lawn care, have lots of arborvitae that need feeding and have ready access to water at the fertilizing site.
Fertilizer spikes are another type of water-soluble solid fertilizer, but in this case the fertilizer is compressed into one solid spike a few inches long. When planted in the ground, the spike slowly dissolves and feeds the arborvitae for weeks or months.
Spikes are more expensive per unit than granular fertilizer, but they have a lot of benefits to offer. They are pre-measured and have a less “messy” appearance than the granular. For those with pets or kids, you can bury the spike a few inches under the soil or position it in a place that is hard for them to reach. Spikes also are less likely to be swept or blown away from the root zone than granules.
I personally prefer the spikes- I love that they’re easy to use, there are no granules around for my kids or animals to get into and one application lasts a long time.
Who It’s Best For:
This is a great choice if you want to take all the guesswork out of fertilizing your arborvitae, you have kids or pets that spend time near the arborvitae or you just want to avoid the look of granules at the tree bases.
Liquid fertilizers can be good for arborvitae, but not necessarily as a main fertilizer. Liquids tend to be less concentrated than solids, and because they don’t dissolve over time, you’d need to reapply frequently.
I do recommend liquid fertilizers, but primarily to give arborvitae a “boost” of micronutrients once or twice during the growing season. Fish emulsion and Liqua-Dirt are useful liquid fertilizers.
Who It’s Best For:
You want to use an organic formula, or you want to give your arborvitae a gentler nutrient boost.
Best Fertilizers for Arborvitae
1. Vigoro All Season Tree, Shrub and Evergreen Fertilizer
This granular fertilizer is a balanced, all-purpose fertilizer for evergreens. The NPK of 16-4-8 provides plenty of nitrogen and potassium, which are generally less available in the soil than phosphorus. It is a good size at an affordable price point that you’ll be able to use on your arborvitae as well as other trees and shrubs.
- High nitrogen is ideal for vibrant color
- Safe to apply a couple of times per year
- Possibly too much nitrogen for some sites
2. Jobe’s Fertilizer Spikes: Evergreen Tree
With an NPK of 13-3-4, this is a great choice for arborvitae growing in soil that has been amended or fertilized before.
Place these spikes in early spring, and you won’t need to fertilize all growing season. You can also stick these in the ground in the fall to take advantage of the winter snow or rain.
One thing to point out is that these spikes can be hard to insert into hard soil. If the ground around your arborvitae is compacted, you may need to get a shovel or bulb auger out to make a hole. A good tip I can share is to wait until a nice soaking rainfall to stick these into the ground- you’ll have a much easier time inserting them.
3. Scotts Evergreen Flowering Tree & Shrub Continuous Release Plant Food
With an NPK of 11-7-7, this fertilizer has a higher dose of phosphorous and potassium, making it ideal for arborvitaes planted in poor soil. And if your arbs are interplanted with acid-loving plants like rhododendrons, dogwoods, or hydrangeas, they’ll also like this fertilizer.
This one needs to be applied more often than Jobe’s or Vigoro, but that’s a small price to pay for such a robust dose of phosphorus and potassium. And although it is tempting, don’t apply more at a time to make it last longer—this can create a buildup of salts in the soil that results in “fertilizer burn” on your arborvitae.
- Affordable price point
- Great for soils that are low in all nutrients
- Good for other acid-loving plants
- More frequent application
When to Fertilize Arborvitae
Arborvitae are not especially heavy-feeding plants, so they don’t need a lot of fertilizer.
When planning your fertilizing strategy, make sure to take your tree’s age into consideration.
Stacie Krljanovic, Houston, Texas-based head groundskeeper and consultant at Patio Productions, says you can skip feeding young trees altogether. “Avoid fertilizing newly planted arborvitae trees until they have become established, usually after one year. Over-fertilization of newly planted trees can cause root burn and may inhibit the tree’s growth.”
Once your arborvitae have had the chance to settle into their second season, you can safely fertilize in the early spring and late fall. This gives the tree lots of nutrients to produce healthy foliage during the growing season and maintain a strong root system during the dormant season.
How to Fertilize Arborvitae
No matter which type or brand of fertilizer you choose, the right preparation, application and after-care make all the difference.
Here’s how to fertilize your arborvitae for the best results.
Preparing to Fertilize
Before applying any fertilizer formula, getting the ground properly prepped is a key step. If you’re using granular fertilizer, it’s a good idea to lightly rake or carefully use a shovel to turn the soil under your arborvitae to help the granules integrate with the soil. But make sure you use a gentle touch- you don’t want to damage the roots.
For any fertilizer type, soak the soil thoroughly before application, all the way out to the edge of the tree’s drip line. Water is absolutely essential for the fertilizer to soak deeply down to the roots, and it also helps prevent fertilizer burns by distributing the nutrients evenly across a larger area instead of concentrating in one spot.
Using Granular Fertilizer
Measure out the right amount of fertilizer per the package instructions. Sprinkle the granules with a hand spreader, or just by hand (make sure to wear gloves). Apply the granules around the entire tree, out to the drip line.
Use your hand or a rake to scratch granules into the soil, then water them in generously.
Using Spike Fertilizer
Depending on the size of your tree you may need multiple spikes per tree; place these an equal distance around the tree.
If the soil isn’t soft enough to easily push the spikes into the ground, use a trowel to dig a small hole for each spike. Bury spikes if necessary to prevent pets or children from tampering with them, or you can use a hammer to gently drive them into the ground.
Using Liquid Fertilizer
Apply liquid fertilizer after rain or irrigation; the roots will be able to absorb more liquid nutrients from moist soil. Dilute the fertilizer in water according to directions, then pour in one or more spots around the edge of the root ball, at least a foot away from the trunk.
After Fertilizing Care
Watering was a key pre-fertilizing step, and it’s just as critical after you apply the fertilizer. Noah James, owner of Liberty Lawn Maintenance in Vancouver, British Columbia says, “It’s paramount to keep your trees well-hydrated so that the fertilizer gets absorbed into the roots and soil. Make sure to give your arborvitae deep irrigations several times each month to maintain hydration levels.”
Noah also recommends mulching your trees- aged wood chips or cocoa hulls are a couple of good options. “Mulching is a great way to add an extra boost of nutrition as well as help protect your trees from outside elements. Mulch can also help prevent weeds that can otherwise compete with your arborvitae by taking away vital nutrients they need for growth.”
It’s a good idea to inspect your trees frequently for signs of disease or pest infestations- arborvitae are vulnerable to both. Finally, Noah suggests trimming your arborvitae once or twice a year to keep an attractive shape and remove any unhealthy growth.
This video from Type 5 Reviews shows some ways to recognize that arborvitae might be under-watered, overwatered or suffering transplant shock:
Frequently Asked Questions about Arborvitae Fertilizer
I hope you’ve found these tips on arborvitae fertilizer helpful. In my experience, fertilizer spikes are the easiest to use, and that’s what I recommend. But how you use the fertilizer is even more important than the type you choose. As long as you fertilize at the right time of year with the proper dosage and plenty of water, you should see good results.
I’d love to hear from you! Do you have any other questions about fertilizing arborvitae, or maybe you’ve got some tips to share that you’ve discovered along the way? There’s no better way to learn than from others’ experiences, so please feel free to share your thoughts in the comments!