5 Best Boxwood Fertilizers | How & When To Use

Whether you have selected Boxwood shrubs to add formality and elegance to your garden or to provide a quirky edge through intricate pruning, you can be happy with the knowledge that these are relatively low-maintenance plants that need little in the way of human intervention to thrive.

Knowing that Boxwoods are both drought-tolerant and light-feeders can be music to the ears of most gardeners. However, they do require some specific care needs to ensure their vibrant, dense green foliage and a thriving plant year-round. Most notably when and how they are provided with additional nutrients.

In this article, I will be providing you with everything you need to know about the best boxwood fertilizers. I’ve included the details of the top-performing feeds as well as when, how, and why your boxwood needs fertilizing. Read on to find out more.

Best Boxwood Fertilizer

If you’re in a hurry to find the best fertilizer for boxwood, then here is my top pick based on quality, value, ease of use, and performance.

Knowing When To Fertilize Boxwood

Like any other plant, boxwoods have their own set of requirements when it comes to fertilizers. Whether newly planted, established, container-based, or in-ground most evergreens don’t require large quantities of feed throughout the year. 

However, their foliage, roots, and overall health will definitely benefit from the addition of fertilizer in late fall or early spring. 

There are, however, some visual cues that indicate the plant is struggling and needs a little extra help.

• Leaves Turning Yellow: If the leaves turn yellow, it’s a strong indication of nutrient deficiency, most likely nitrogen. The yellowing can occur across the whole plant or in localized patches.
• Slow or Sparse Growth: If you notice your boxwoods are not growing at their normal rate, they may be lacking a few essential nutrients. While boxwoods are naturally slow-growing, you should see fresh growth each spring. A significant decrease in growth should be your cue to apply fertilizer.
• Weak or Brittle Branches: Nutrient deficiencies can lead to weaker branches prone to breakage.
• Chlorosis: Chlorosis is when leaves turn pale green or yellow due to a lack of chlorophyll. This occurs when the plant isn’t receiving enough iron or one of the other essential micronutrients. If this occurs check the soil pH and apply fertilizer.

Choosing A Fertilizer for Boxwood

Nitrogen (N), phosphorus (P), and potassium (K) are the primary macronutrients required for plant growth. The N-P-K ratio delineates the proportion of these nutrients present in a given fertilizer, typically expressed as a series of numbers (e.g., 10-10-10).

For boxwood, I would recommend a slow-release, granular fertilizer with an N-P-K ratio somewhere in the region of 10-6-4. This will provide sufficient nitrogen for foliage development, phosphorus for healthy roots, and potassium which supports various physiological processes for good plant health.

However, I would emphasize that N-P-K is not as critical as many people would have you think. The main focus is to deliver high nitrogen to support the production of chlorophyll and the production of amino acids, the building blocks of proteins and new plant cells. Phosphorus and potassium are required at some level but the ratio depends on the nutrients already present within the soil, or whether you are trying to address a specific problem.  

I should also mention trace minerals, which should not be overlooked when choosing a fertilizer. Elements such as iron, manganese, and zinc all play important roles in supporting the plant’s cell production and photosynthesis.  

Understanding Fertilizer NPK Ratio

The “NPK ratio” is a set of three numbers present on every fertilizer product packaging. These numbers represent the proportion of nitrogen, phosphorus, and potassium available in each product. They are important since different plants require different proportions of each nutrient.

All evergreens including Boxwood need nitrogen (N) in the highest percentage ratio. This is vital for enabling photosynthesis and that all-important lush, dense foliage growth. 

They also require phosphorus (P) to support the development of a strong root structure. The feeder roots of boxwood are extensive and grow just below surface level. This far-reaching network of roots enables them to better seek out water during drought conditions. Boxwood shrubs are susceptible to pest infestations and disease and so they need phosphorus to provide protection. 

In addition, they need potassium (K) to enable them to circulate water, oxygen, and other nutrients effectively especially when exposed to temperature stress either during summer droughts or winter freezes.

Ideal Soil pH

Boxwoods prefer slightly acidic soil with the ideal pH range falling between 6.5 – 7.0.

I recommend conducting a soil test before planting and as your boxwood ages and adjusting soil pH accordingly. This will enable your boxwoods to absorb the correct nutrients from the soil and keep these evergreens thriving.

I don’t advise the use of fertilizers recommended for acid-loving plants and shrubs as this tends to lower soil pH which can be detrimental to the growth cycle of evergreens. If you do find that pH levels are too low (i.e. acidic) add lime to the soil and review with a soil test in 3 months’ time.

Types Of Fertilizer

When it comes to fertilizing your boxwoods, you will find three main options available. These include spikes, granules, and liquid concentrate. Each has a slightly different method of application or nutrient release. So let’s quickly take a look at each type of fertilizer and outline when it is best to use it.

Fertilizer Spikes 

Fertilizer spikes represent the ultimate convenience and precision in plant care. With ingredients that have been carefully measured and their ability to feed your plants on a slow-release basis, they can ensure you have time to focus on other gardening necessities such as pruning, mulching, or planting.

Fertilizer spikes need to be applied around the dripline of a plant. It is where the most active roots are located. However, in my experience, it can be easy to damage the feeder roots of Boxwood with the use of fertilizer spikes and so care should be taken if this is your preferred method of application.

This type of fertilizer product is generally considered pricier compared to granules and liquid but might be just what you need if you prefer feeding your plants with a minimum of fuss.

Granules For Top Dressing

Using fertilizer granules to top-dress the soil around Boxwood evergreens is one of the best ways to avoid damaging their feeder roots. These lie just beneath their surface and can be prone to fertilizer burn or damage either by vigorous digging or over-fertilizing. 

The application method requires them to be sprinkled or broadcast over the soil and then raked and watered for effective absorption and distribution into the soil. They offer a slow release of nutrients, often continuing to be effective for between 4 weeks to 3 months depending on the product and brand.

Granules offer a cost-effective method of fertilizing and tend to have a long shelf-life. There’s also little chance of run-off since they get absorbed into the soil once watered in. 

Liquid Concentrate Fertilizer

Whether bought as a ready-to-use formula or as a concentrate that needs diluting with water, liquid fertilizers offer a fast-acting approach to feeding boxwoods and are a great way to boost an ailing evergreen instantly, especially if you have noticed yellow leaves in the lower regions of your shrub.

Use a sprayer or decant in a watering can use as either a foliar ‘tea’ or to apply to the soil for roots to absorb quickly. 

The downside of liquids is that they can contribute to runoff and fertilizer burn if used outside of the manufacturer’s recommendations or applied too often. 

5 Best Fertilizer For Boxwood Reviews

The products on this list have been thoroughly reviewed considering all the things that count when it comes to fertilizing Boxwood: NPK ratios, manufacturer profiles, key ingredients, ease of application, and price.

A few gardening experts also generously shared their knowledge on just which worked best for their boxwoods.

I’ve narrowed my selection down to the best 5 and brought to you the ones that I believe have what it takes to make yours flourish in the same way they’ve rewarded the efforts of dedicated boxwood owners the world over.

Pros     

• Includes patented Bio-tone Microbes for soil health
• Provides 100% organic nourishment for 6 months
• Also an excellent fertilizer for fruit, olive, or nut trees

Cons

• Prone to drying out if not stored correctly

These organic, slow-releasing granules from Espoma provide the perfect blend of macronutrients for Boxwood and will nourish your soil thanks to their patented Bio-tone microbes formula. 

Higher in nitrogen to ensure your shrubs have an abundance of richly green foliage and just enough phosphorous and potassium to tick all the boxes when it comes to strong root growth, effective distribution of water oxygen, and nutrients, and protection against environmental stresses. 

These granules are a decent size as you can see from the photograph below. They are ideal to use as a slow-release top dressing that Boxwoods need and are best applied just below the soil’s surface, within the tree’s drip line. 

In the images below, I used this fertilizer on a row of Boxwood that subsequently got snowed on quite heavily during the winter after I fed them. My concerns about damage caused by frost damage and subsequent loss of new growth were quickly put to rest come spring when the Boxwood bounced back with new growth and no die-back.  

How To Use

Apply the recommended amount per shrub diameter along the dripline. Apply in late fall or early spring. Water well after each application. If you have topiary hedges you can apply a top dressing along the hedge, just as I am above in the image, at a rate of one handful per yard. Then lightly dig it in or rake it over.

Pros

• Ideal for transplanted boxwood trees
• 100% natural ingredients and no harmful chemicals
• Helps improve soil condition

Cons

• We May need to supplement with more phosphorous for enhanced root development

Brought to you from a brand renowned for its world-class conservation and environmental values, this slow-release Tree & Shrub Fertilizer from Down to Earth will not only support lush green foliage growth and support overall health but will also help to improve soil conditions too. 

There’s the fact that it contains no less than 11 species of mycorrhizal fungi which – when dissipated into the soil – enables roots to absorb nutrients more effectively, especially when newly transplanted.

It also contains kelp meal to boost the immunity of plants, azomite to improve the results of other trace micronutrients, and langbeinite which contains magnesium, sulfur, and potassium – all of which Boxwood needs to drive up protection against transplant shock and temperature stress.

How to Use

Before planting (or transplanting), blend 1 – 3 cups thoroughly into the back soil. If applying to a mature plant, simply dig holes ranging from 3 – 6 inches in depth in a grid formation and fill each with 1 – 2 tablespoons.

Pros     

• Good for lowering soil pH is too alkaline
• Ideal for iron deficiencies in Boxwood
• Slow-release for long-term absorption

Cons

• It May attract pets and wildlife due to the ‘organic’ smell

These slow-release granules work best where a soil test has revealed a high pH range that needs lowering or where evergreens have Chlorosis – a disease that causes the yellowing of leaves that is most often caused by a nitrogen or iron deficiency.

Since it is a granular formula that can be worked into the soil and absorbed over time, this fertilizer is unlikely to cause fertilizer burn and can be used both on young Boxwood shrubs at the time of planting and on mature evergreens that need a boost.

Thanks to the 11% of nitrogen and 7% ratio of phosphorus and potassium when used on a Boxwood with yellow leaves I found the discoloration soon disappeared, and new buds began to form thereafter. 

How to Use

Apply ½ tablespoon per square foot (or 1 cup for 35 square feet) around your boxwoods. The product must be applied within the dripline of each plant.  Gently rake into the soil and water abundantly.

Pros

• Ideal for use on larger individual specimen boxwoods
• Mess-free fertilizing with no strong odor
• Slow-release fertilizing for year-round results

Cons

• Can damage roots if incorrectly inserted

Convenience and effectiveness all rolled into one, Jobe’s Evergreen Fertilizer Spikes come with the promise of easy application and the ability to feed your plants for months at a time. 

There’s no need for measuring or mixing here. All I do is simply insert them into soft soil around the shrub drip line. The slow release of nutrients will feed your boxwoods for an entire season meaning all you have to do is sit back and watch it work its magic.

I recommend using fertilizer spikes if you have large specimen shrubs where one or two spikes will feed you boxwood for 8 weeks. Due to their size and compressed design, spikes are no use when looking to fertilize a hedge. I prefer to use a granular feed when fertilizing my boxwood hedge, as it provides broader coverage and all of the plants get fed.

As you can see from the photo below my dog took an interest in the fertilizer spikes due to their organic smell. That’s another big advantage of using spikes, you can hammer them completely into the ground out of reach of dogs or any other garden wildlife.

How to Use

Water the soil around your boxwoods to soften the ground. Insert the spikes at their driplines. You will need to use one spike per 3 feet of each shrub’s height. Position the protective rubber cap on the end of the spike to prevent it from splintering, then hammer them completely into the ground.

Pros

• Can encourage moisture retention
• Encourages root development and robust foliage growth
• Provides 12-month protection from pests
• Helps shrubs retain moisture

Cons

• It May require several applications

Fertilize and protect your boxwoods in one go with this dual-purpose product which will improve their health with its nourishing formula while keeping voracious pests at bay.

This product has been specifically manufactured to enable your boxwoods to produce the energy they need to grow healthy roots and foliage, as well as conserve moisture in their cells – especially during periods of drought or winter frosts.

In addition, this formula has been developed to keep destructive bugs – such as the emerald ash borer and the Japanese beetle – away from pest-prone Boxwoods. 

If you want to ensure your boxwoods are fully nourished while enjoying a pest-free existence, this might be the product you need.

How to Use

Apply 1 fluid ounce per inch of circumference and mix with a gallon of water.

Verdict: Best Boxwood Fertilizers

A host of fertilizer products are suitable for feeding Boxwoods depending on your gardening needs and growing concerns. 

Whether you are just about to plant a border of Boxwoods or you have a row of mature shrubs, I’ve got you covered.

I’m a huge fan of Espoma’s slow-release TreeTone granules. They are a great way to gently nourish the soil around your Boxwoods and can be used as a top dressing so that you can avoid damaging the surface roots of these shrubs.

Alternatively, choose Down to Earth’s Tree and Shrub Fertilizer to gently boost foliage and root growth and generally support the health of your boxwoods using only 100% natural ingredients. 

Here are the results… my boxwood hedge is showing lots of new bright green growth and looking thick and healthy. I will give it one more feed after I have pruned it back to square off the edges.

When to Apply Fertilizer to Boxwood 

The roots of Boxwoods develop most extensively during the late fall, winter, and early spring. As a result, late fall and early spring are the best times to fertilize them. 

They should not be fed in the late summer or early fall since this may encourage them to produce new growth which will become susceptible to frost and burn during the prevailing, cooler seasons.

How To Fertilize Boxwood Shrubs

Apply fertilizer around the dripline since this is where their most active roots are located.

Mulch first and then apply fertilizers over the top to prevent their surface, and feeder roots from damage, and fertilizer burn.

I highly recommend getting your soil’s pH checked out before fertilizing and ideally before planting to understand any soil imbalances or nutrient deficiencies. Remember, Boxwoods thrive between pH values of 6.5 – 7).

How Often to Apply Fertilizer

Boxwoods are light feeders and – depending on the product you buy – may only need to be fertilized once a year if soil conditions are correct and where little or no deficiencies are detected. 

For ailing Boxwoods including exposure to temperature stress or nutrient deficiencies that are likely to cause yellowing of leaves, I recommend applying liquid fertilizer. 

This will not only allow nutrients to be absorbed quicker but also provides the option of repeating the application soon after and in accordance with the manufacturer’s guidelines. 

Overfertilizing Boxwoods

Since Boxwoods are not heavy feeders and do not need high concentrations of nutrients to thrive, excessively applying fertilizer will result in an increased concentration of salts in the soil. 

This may not only harm the roots of your boxwoods by making them dry up but also prevent them from being able to draw nutrients and moisture from the soil. As a result, their leaves, twigs, and branches may desiccate.

FAQ’s Fertilizing Boxwood

Why are my Boxwoods turning yellow?

Your boxwoods may be turning yellow because of over-fertilization or a lack of nitrogen. Fungal infections such as Cylindrocladium buxicola also known as Boxwood blight may also be a possible cause.