When to Use 17-17-17 Fertilizer? | How to Use Triple 17

When and how to fertilize plants is an essential but often misunderstood part of gardening. Plus, finding the right fertilizer formula can be time-consuming and complicated even for the experienced gardener.

A 17-17-17 fertilizer offers a balanced formula with the necessary macronutrients in a ratio that many plants need. Keep reading to learn more about the fertilizer’s components and why they’re important, methods for applying it, and what plants can benefit from this balanced formula.

Understanding 17-17-17 Fertilizer Label

Labels contain a lot of information, but thankfully, these labels are nationally standardized. Once you understand one, you’ll understand them all.

The bold numbers at the top designate how much of the key nutrients will be supplied by the fertilizer, and together they’re called a fertilizer grade. 

The first number is always nitrogen, the second number is phosphorous, and the third number is potash, also referred to as potassium. 17-17-17 fertilizer, or triple 17, contains an equal volume (17%) of each nutrient. 

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N-P-K Ratio

NPK stands for:

  • Nitrogen
  • Phosphorus
  • Potassium 


There are some fundamental reasons why plants need nitrogen. Most importantly, it is what drives the production of chlorophyll. Chlorophyll is what gives plants their lush greenness and what enables them to develop cells for healthy growth and development. 

It also fuels the production of food by turning stored energy within a plant into starches and carbohydrates.

In addition, plants need Nitrogen to enable them to appropriately utilize proteins and enzymes so they can regulate water and nutrient uptake effectively. Without it, they would not survive.

Like all the primary macronutrients, the amount of nitrogen necessary to promote healthy growth and their green color isn’t universal. Indeed, it varies significantly from one species of plant to another. 


Phosphorus is a catalyst for all the processes within plants. It is essential to photosynthesis as this is what activates that all-important process of converting starches and carbohydrates into food. 

It’s a crucial part of both DNA, which holds the memory of how the plant grows and reproduces, and RNA, which helps the plant read and react to the DNA in plants. 

Phosphorus bonds and links DNA and RNA together to ensure that the plant can use the information for building proteins, using sunlight to produce and store energy efficiently, and supporting reproduction. It’s a key part of bud, flower, and fruit development.

It also supports the development of the plant from seedling through to mature adult plants in developing strong cell walls and a robust root system. 


Potassium (or potash) affects the quality of the plant. It enhances plants’ resistance to disease and improves overall robustness by strengthening their root system. It also helps plants resist drought and survive cold weather by building cellulose in the plant.

Adding potassium to fertilizer also boosts the qualities of the other nutrients it’s paired with. For example, potassium works with nitrogen by stimulating the protein content that nitrogen develops. It can also activate enzymes that phosphorus helps the plant read through its DNA.

What Is Triple 17 Fertilizer Used For?

Triple 17 fertilizer is often used commercially to strengthen and fortify growth and enrich the soil of many crops as well as plants, trees, and shrubs. 

As a domestic use fertilizer, it can be used to fertilize lawns, vegetable gardens, trees, shrubs, and plants to help with growth. It can enhance green foliage, encourage robust roots, as well as protect against pests, diseases, drought, and freezing temperatures. 

Why Use a Balanced Fertilizer?

A balanced fertilizer means all nutritional elements are measured equally. In this case, a triple 17 fertilizer contains 17% for nitrogen, 17% phosphorous, and 17% potassium. 

Balanced fertilizers can be used to improve depleted soil before planting or boost new growth at the start of the growing season for established plants. 

Adding a balanced fertilizer can help plants to establish themselves as they begin to grow by encouraging overall plant and root growth.

Fertilizer Types

Whether you prefer organic or synthetic, each form of fertilizer has its own advantages and application methods. 

Liquid Concentrate

Liquid concentrate fertilizers typically need to be diluted with water. Although they also come as ready-mixed formulas that require no diluting and can be used straight away and administered with either a hose, a sprayer, or a watering can. 

The most significant advantage of liquid fertilizers is how quickly plants absorb them. Once applied, they begin working almost immediately and are a great way to boost your plant’s health, with benefits almost immediately.

Be careful. Liquid concentrate is prone to run-off, and this can potentially lead to contamination of local water sources, which are hazardous to the environment.

Water Soluble Powder

Water-soluble fertilizer comes as a powder that can be sprinkled directly into the soil or diluted with water and sprayed. 

It’s a fast way of addressing your plants’ needs but carries the risk of root burn due to its highly concentrated and fast-acting nature. Dilute the fertilizer up to a quarter of the dosage for adult plants when feeding very young plants to avoid burn.

These types of fertilizer are also prone to run-off and need to be applied more frequently due to their fast absorption rates.

Slow-Release Granules

Slow-release granular fertilizer is a commonly used type of fertilizer and one that most people are familiar with. 

The granules of a slow-release fertilizer are broken down gradually by microbes in the soil. This means that the nutrients within the granules take a longer period to become absorbed into the soil and by the roots of plants. 

One application of this type of fertilizer can continue to be effective for between 30 to 90 days depending on the manufacturer’s recommendations. 

Always read the labeling and instructions for any type of fertilizer to understand how best and how much to apply. Bear in mind that some slow-release fertilizers will need to sit for up to 48 hours before adding water, while others need watering immediately.

Fertilizer Spikes

As its name implies, fertilizer spikes are a type of solid fertilizer that can either be pushed or hammered into the ground. They are pre-measured for your convenience, and as a bonus, they’re easier to store than heavy bags. 

Just like slow-release granules, the spikes break down over time and distribute nutrients gradually into the soil, where the plants’ roots will absorb the nutrients quickly.

They usually work out to be more expensive than other fertilizer methods since you need more spikes for larger trees or areas of coverage. On the flip side, they don’t produce any odor so are a convenient option to use around pets. 

How and When To Use Triple 17 Fertilizer

How and when you use fertilizer varies significantly from one plant to the next and from one fertilizer product to another. Not all plants need a balanced fertilizer such as Triple 17, so always ensure you read the directions thoroughly so that you are applying the product safely and at the recommended application rates.

Trees and Shrubs

An application of 17-17-17 fertilizer added to the planting hole of newly planted trees and shrubs will provide them with the nutrients needed to boost root growth and support healthy growth in the early and fast-growing stages of their development. 

For larger and more established trees and shrubs, adding Triple 17 to nutrient-poor soil will improve their color, correct drooping and wilting, and provide an effective defense against pests, diseases, drought, and also plummeting winter temperatures. 

If you compost or mulch regularly around established trees, they typically don’t require any additional fertilizing. However, if foliage begins to yellow, brown, wilt, or drop then you should conduct a soil test to understand if any nutrient deficiencies exist, then address them accordingly.  

Fruit Trees

While a balanced fertilizer won’t harm your fruit trees, they do require a higher dose of certain macronutrients at specific times during their growing cycle. 

For example, more nitrogen at the beginning of the growing season will support new growth, while higher levels of phosphorous before bud set will help to form flowers and fruits as the season progresses.

The addition of potassium in the fall will help to protect fruit trees against pests and diseases as well as encourage a plentiful yield and a harvest with a longer shelf life. 


Whether grown in the ground or in pots, containers, or hanging baskets, bedding plants, border flowers, and blooming ornamental plants all need regular fertilizing with a balanced feed to maintain that all-important vivid, summertime display of color. Choose a liquid concentrate 17-17-17 fertilizer here, especially if your soil is anything less than nutrient-rich. 

When soil quality is good, you can afford to lower the N-P-K to a 10-10-10 fertilizer or even a 5-5-5 fertilizer. This will avoid any forced growth or flowering out of season. 

Annuals typically require fertilizing as soon as they begin to grow, so consider fertilizing the soil before planting. As perennials keep blooming after annuals die, you can continue to use a balanced fertilizer from spring through to autumn and until flowering has finished.

Vegetable Gardens

Not all vegetables require an even balance of nutrients, and their fertilizing needs all vary depending on the season, and the vegetable type.

If you have tested your soil and you know it is lacking in nutrients, then a Triple 17 fertilizer can be worked into the soil pre-planting. 

Once plants are established, you will need to be more selective with the N-P-K ratios of your fertilizers. For example, use a high nitrogen fertilizer for leafy vegetables such as cabbage and spinach to encourage plenty of foliage and a rich-green color. 

However, avoid using high nitrogen fertilizers for root vegetables such as carrots and beets as this will prohibit growth below the soil and encourage lots of unnecessary foliage growth. For this variety of vegetables, use a fertilizer with more phosphorous and potassium instead.  

Likewise, fruiting edibles such as tomatoes, squash, and melons need more phosphorus and potassium in the earlier stages of bud development. 

Avoid a balanced fertilizer for these plants and instead, select a high phosphorus fertilizer or a specific tomato fertilizer, or a fertilizer for pumpkins and squash if you want to ensure a plentiful and healthy yield.


A good rule to remember when fertilizing houseplants is to fertilize only when they’re actively growing, and not in their dormant period. 

I would avoid a full-strength 17-17-17 fertilizer for any type of houseplant. If it’s all you have then you could dilute it to a third of the strength to avoid any potential for root or leaf burn.

Lawn and Grass

Lawns and grass can benefit from triple 17 fertilizer, especially to balance the soil after planting new sod or sowing grass seed as this will help establish healthy growth and root development. It will also help to protect new plantings from adverse weather and protect against pests and diseases. 

For established lawns, fertilize with Triple 17 in spring when it is actively growing and apply more in the fall. Applying fertilizer before winter dormancy will help it recover from any damage sustained during summer droughts and repeated foot traffic.

Avoid 17-17-17 fertilizer during the summer months. This is when your established lawn needs a high nitrogen fertilizer to help promote healthy growth and encourage a more vibrant color.

17-17-17 Fertilizer for Garden FAQs