When To Use 16-4-8 Fertilizer | How To Use It

Adding nutrients to the lawn and garden with a good quality fertilizer can make all the difference to plant health and vitality during the growing season and throughout dormancy. 

For evergreen plants and grasses, using a high-nitrogen feed such as a 16-4-8 fertilizer will help to improve the color, texture, root growth, as well as their resistance to extreme weather and pests or diseases.

As well as protecting overall health, fertilizer with an N-P-K of 16-4-8 can be applied to any grass type and almost all evergreen trees, plants, and shrubs. But, before you begin, here’s the lowdown on how and when to use it, plus why you need it in your garden or yard.

Understanding 16-4-8 Fertilizer Label

Finding a fertilizer that meets your garden’s needs and your expectations can seem daunting, especially with so many products to choose from. The game-changer is when you understand the labeling as this can save you a whole lot of time, effort, and expense. 

Aside from directions for use, almost all labels state the product’s NPK. This stands for nitrogen, phosphorus, and potassium and these are the primary macronutrients that all plants need to live and grow. 

In addition, the label should list the details of all filler compounds plus any included secondary micronutrients such as iron, sulfur, zinc, copper, calcium, and magnesium, that help to support plant health.

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N-P-K Ratio

An N-P-K ratio identifies the proportion of nitrogen, phosphorus, and potassium contained in the fertilizer. It is always best that you perform a soil test to have the best idea of what your dirt might be missing.

This particular fertilizer consists of 16% nitrogen, 4% phosphate, and 8% soluble potash. To easily understand what these percentages mean, assume you are purchasing a 100lb bag of fertilizer. Based on this ratio, you would find:

  • Nitrogen: 16 pounds
  • Phosphorous: 4 pounds
  • Potassium: 8 pounds


Plants need nitrogen for the primary reason driving the production of chlorophyll. Chlorophyll is essentially the lifeblood of plants: It’s what generates the production of food by turning stored energy into starches and carbohydrates; It helps to fuel a healthy support system and successful cell development; It’s what gives plants their color.

Nitrogen also helps plants to regulate water and nutrient uptake by enabling proteins and enzymes to be correctly resourced. 

High-nitrogen fertilizers are most often used for non-flowering plants, evergreens, and lawns.


Phosphorus is essential to photosynthesis as this is what triggers the process of converting starches and carbohydrates into food.

Bud production in flowering plants, as well as robust root systems, is also a responsibility of the macronutrient phosphorus. In addition to this phosphorus generates the proteins and enzymes that nitrogen needs to regulate water and nutrients.


Potassium is needed to ensure that water, nutrients, and photosynthesized food are circulated throughout plants. 

Potassium increases 

Where potassium levels are sufficient, plants are able to conserve moisture more effectively. This enables them to be better protected against disease and environmental stress resistance. 

This benefit is most effective in encouraging a lawn’s tolerance for cold winters while dormant.

16 4 8 Fertilizer Type

Fertilizers are produced in a range of different formats. Choosing the correct application method for your project comes down to personal preference as well as helping to ensure you are serving your plant’s particular needs.

Liquid Fertilizer Spray

You can administer liquid fertilizers with a handheld sprayer or as a spray attachment for your hose pipe. Apply it to the soil for roots to absorb or use it as foliar feed if you spray it on leaves and stems. 

Liquid fertilizers are fast-acting and effective. They are the easiest way to get nutrients to your lawn and plants. 

They offer an instant boost of nutrients and can be used if your plants are looking a little lackluster, during the planting process and throughout the season when deficiencies arise. 

Keep in mind that while the results are seen almost immediately, they are prone to run-off and so you need to apply them more frequently.

Run-off is when nutrients leach quickly into or away from the soil. This can be potentially hazardous for surrounding plants or if the fertilizer product seeps into nearby water sources. 

Slow-Release Granules

Slow-release granules come in pellets and coarse powders that are broken down by the microbes in the soil over several weeks or months. 

Some gardeners prefer to use slow-release granules with new plants and for lawn care since they will gradually release without the need to re-fertilize frequently.

This type of fertilizer provides less chance of fertilizer burning or scorching your plants and also less potential for water contamination.

Water Soluble Powder

Ideal for hydroponic gardens, this powder is designed to be added directly to the water supply for your plants. The plant gets suspended in water rather than soil. It rests in a permeable pot where the roots extend into flowing water. 

Another method of using water-soluble fertilizers is to dissolve them in water and apply it using a watering can. This helps roots to absorb the nutrients directly once it seeps through the soil. 

Fertilizer Spikes

Similar to slow-release granules, fertilizer spikes break down over time. They need to be pressed or hammered into the soil around plants and once activated by moisture they will release nutrients into the soil. 

They provide a convenient, mess-free, and easy-to-use fertilizing solution, and you only need to apply them a few times a year. 

Because fertilizer spikes are inserted into the soil, they can be sited near the roots of plants. If positioned too close, it can create the potential for over-fertilizing or burning roots in some cases.

What Is 16-4-8 Fertilizer Used For?

16-4-8 fertilizer promotes rapid green growth. It can replenish the soil and strengthen flowerless trees, shrubs, and house plants. This N-P-K ratio works well for lawns as it supports optimal nutrition for grass. 

The nitrogen gives grass that beautiful green color and keeps it healthy and is ideal for evergreens and leafy green plants with plenty of foliage.

Phosphorus encourages root growth, making it a valuable fertilizer for the start of the planting season. 

It is worth bearing in mind that new seeds and young plants may become scorched by high nitrogen fertilizers, so it is important to follow manufacturers’ guidelines on how much to use. Also, not all states allow for phosphorus use in fertilizers.

The moderate potassium level provides protection against drought and high temperatures in summer as well as protection against frost and snow in the winter. High potassium fertilizers also help to protect and prevent disease and pest infestations.

Nutrient Deficiency

One of the first signs of a nutrient deficiency is leaf discoloration. If your plant has yellow leaves with green veins, your soil likely lacks nitrogen. Purple-tinged leaves indicate a phosphorus deficiency. When the edges of older leaves become brown or yellow, you may need more potassium.

You can also perform soil tests to determine how much of these macronutrients your soil lacks. Soil tests can give a profile of the precise nutrient levels to help you choose the ideal fertilizer for your plant.

Lawn and Grass

A liquid or granular 16-4-8 fertilizer designed for lawn care will encourage root growth, weather resistance, and deep green shades with most fertilizer brands being safe for all grass species. 

Through regular watering and fertilizing, you can grow, texture, color, thickness, ness, and resilience of the grass. Plus, enriching the soil helps the roots absorb nutrients to improve the grass’s health.

You can use 16-4-8 fertilizer on your lawn and grass all season long. The moderate phosphorus levels aid in root growth and establishment in the early growing season. 

Your lawn will benefit from the nitrogen in the summer as this will encourage strong, dense, green grass. Lastly, the potassium levels encourage temperature and drought resistance and protection from pests and adverse weather through the fall and winter months.

Trees and Shrubs

Green, leafy trees and shrubs are great candidates to benefit from this fertilizer’s high nitrogen content. You can expect your evergreen trees and shrubs to look their best and be their healthiest thanks to the high nitrogen content. 

If you have flowering shrubs and fruit trees, they can benefit from the 4% phosphorus in a 16-4-8 fertilizer. In addition to root growth, phosphorus improves seed production and flower formation. Both the phosphorus and potassium will improve the resilience of your trees and shrubs to protect them from disease and extreme temperatures.

Flowering Plants

If your flowering plants have a nutritional deficiency, you might want to invest in using a 16-4-8 fertilizer if you have some available. The N-P-K content can help with flower formation, seed production, fruit development, root establishment, and plant resilience.

You may prefer, however, to invest in a high phosphorous fertilizer to encourage bud and flower development to its full potential.

Annuals consume nutrients quickly, so you will want to fertilize your soil before planting. Perennials need year-round nutrients, so you should apply fertilizer regularly.

Vegetable Gardens

Leafy vegetables benefit from the high nitrogen content. The phosphorus and potassium levels also help these vegetables grow healthy roots and protect themselves from pests, weather events, and diseases. 

Root vegetables perform better with more phosphorus and potassium. Their complex root system requires more phosphorus, and they need a higher level of immunity to diseases and pests.  


While you can use 16-4-8 for house plants, generally, you’ll want to go with a balanced N-P-K fertilizer with ratios between five and 15. If you use it on houseplants, you should only apply it to non-blooming plants. Also, ensure you dilute the fertilizer in water to at least half of its concentration.

How and When to Use 16-4-8

How you apply your fertilizer differs based on the product and your plant. Ensure you read the directions thoroughly to use the fertilizer correctly.

16-4-8 Application Rate

The application rate depends on how quickly your plant consumes the nutrients:

  • Trees and shrubs: apply near the beginning and end of the growing season
  • Flowers: use slow-release granules according to the manufacturer’s recommendations
  • Vegetables: use on leafy vegetables at the beginning of the growing season 

Can You Use Too Much 16-4-8 Fertilizer?

Yes, you can use too much 16-4-8 fertilizer. The high nitrogen concentration can scorch your plants if you over-apply it. Nitrogen burns can reduce the quality and quantity of your plants. Any produce or flowers can become underdeveloped, and the plant will seem less lush and green.

16-4-8 Fertilizer FAQs

Do you have more questions about 16-4-8 fertilizer? Keep reading for the answers.

Verdict: When Is 16-4-8 Fertilizer Best?

16-4-8 fertilizer is a terrific option for lawns, evergreen trees, plants, and shrubs. 

The high nitrogen content promotes green growth for healthier and more vibrant plants. The phosphorus helps plants grow new roots, seeds, fruit, and flowers, while the potassium makes them strong and resilient against extreme weather, diseases, and pests.

Before investing in a fertilizer, get a soil test to see if you need to replenish the nutrients in these proportions.