12-12-12 Fertilizer | How and When to Use Triple 12

Every good gardener knows they need to fertilize their soil to help their plants, flowers, vegetables, and lawns perform well. But buying fertilizer can be complex with the myriad of labels, application methods, and understanding which one is best and for what parts of your garden. 

Using a triple 12 fertilizer can offer a balanced feeding solution for many gardening needs and this article will cover when is 12-12-12 fertilizer best, what it’s used for, as well as how and when to apply it.

Understanding 12-12-12 Fertilizer Labels?

The label on a fertilizer should always have three numbers, presented as a ratio of the different elements within it. 

Numbers on Fertilizer Packaging Explained in 60 Seconds

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N-P-K Ratio

The three numbers you will typically see on fertilizers refer to the ratio of N for nitrogen, P for phosphorus, and K for potassium within it. Each of these macronutrients is essential for proper plant growth and in turn, they have unique responsibilities for different aspects of a plant’s development.

Knowing the N-P-K ratio for fertilizer will enable you to select the right product for your particular application. To determine exactly how much of each nutrient is in your fertilizer, you can do some simple multiplication to find the total amounts. 

For 12-12-12 fertilizer in a 50-pound bag, the maths might look like this:

First, multiply the number of nitrogen (12) by the total weight of your bag of fertilizer (50). 

12 x 50 pounds = 6 pounds 

Since this is a ‘straight’ ratio fertilizer, all of the nutrients are in the same quantity. So you just multiply by the same numbers for each nutrient. 

  • Nitrogen: 6 pounds
  • Phosphorus: 6 pounds
  • Potassium: 6 pounds

The rest of the package’s weight comes from fillers like sand, limestone, and other micronutrients, organic matter, or chemicals. 


Nitrogen aids plants with leaf and stems growth. A plant without enough nitrogen will suffer from poor cell development, weakened enzymatic activity, and a lack of green pigmentation in the leaves. 


Phosphorus is essential for helping plants convert the energy from the sun (or another light source) into the chemical energy a plant needs to sustain life. That process takes the name of photosynthesis, and without it, a plant will die. 

Phosphorus is also essential for proper flowering and root development. 


An overall healthy plant requires adequate potassium. It is an immunity booster, helping plants ward off diseases and the effects of insect activities and other issues that can lead to poor growth and production of flowers and fruits. 

Fertilizer Type

Fertilizers come in a few different types for different application methods. They each have advantages and disadvantages. 

Liquid Concentrate

A fertilizer sold as a liquid concentrate needs dilution before application. Some varieties come with an attachment for a garden hose, so you can easily spray a solution of the concentration and water on large areas of your garden or lawn. 

For other liquid concentrate applications, a gardener would use a container, like a watering can, to mix the fertilizer with water and then distribute it appropriately. 

Water-Soluble Powders

Fertilizers also come as water-soluble powders. This type of fertilizer is the backbone of fertilization in hydroponic gardens. 

This style of gardening uses water instead of traditional soil as a growing medium. The plant sits suspended in a permeable pot, with its roots extending into a flowing stream of nutrient-rich water below. 

Hydroponic gardeners carefully dissolve their fertilizers into the water supply, bringing the nutrients directly to the roots of the plants in precise quantities for optimal and nearly instantaneous feeding. 

Another application method for water-soluble powders is to dilute them in water. The powder can be measured into a watering can and topped up with the required quantity of water.

Slow-Release Granules

Slow-release granules are fertilizers with an extended impact on soil nutrition. One single application can last for days, weeks, or even most of a growing season. A protective, slow-dissolving coating protects the nutrients inside the granule. 

As the coating breaks down over time, the nutrients inside are released into the soil. This sort of fertilizer application is much longer-lasting than liquid applications. 

Fertilizer Spikes

Fertilizer spikes are also time-released. But instead of small granules, the fertilizer is compacted into a block, spike, or stick. These are long and thin with a pointy end that is pushed or hammered into the ground. They break down over time, delivering nutrients to the soil in a gradual process. 

What is Triple 12 Fertilizer Used For?

Triple 12 fertilizer is a straight or balanced fertilizer. Each of its individual macronutrients of nitrogen, phosphorous, and potassium is available in equal quantities. 

Why Use a Balanced Fertilizer?

Balanced fertilizer is ideal for setting a solid nutritional foundation in a garden for trees, lawns, or shrubs. But remember that some plants need specialized ratios for optimal production. For instance, you might want a high potassium fertilizer for flowering plants or a higher nitrogen content for acid-loving plants. 

A balanced fertilizer is a great place to start for general soil enrichment and healthy plant development. 

Trees and Shrubs

The nutrient requirements of trees and shrubs can vary depending on the species, the soil in which it is planted, its location, and also any nutrient-greedy neighboring plants. A solid foundation of an all-purpose 12-12-12 fertilizer can be a good place to start, but always research the particular tree or shrub and adjust the nutrients accordingly. 


Flowers tend to need well-rounded development throughout the growing season. Annuals are likely to consume a lot of nutrients as soon as they are in the ground and planted, so consider having a balanced fertilizer worked into your soil before planting. 

Perennial flowers will need nutrients all year, so consider more routine applications to keep them healthy and vigorous both above and below ground. 

Vegetable Gardens

Vegetable gardens tend to need specialization. For instance, if you want to promote root development in your carrots, you should look for a fertilizer with more phosphorus. Conversely, if you want to emphasize the leafy development of your spinach, consider using a fertilizer rich in nitrogen. 

A 12-12-12 fertilizer is a good starting place, but too much fertilizer – either too often or in excessive doses can cause damage, fertilizer burn, or even devastation to an entire crop.


Houseplants need nutrients too. Their soil isn’t replenished by the decay of natural nutrient boosters as it is outdoors, so you’ll have to make sure you establish a strong base, making a 12-12-12 fertilizer an effective choice. 

Lawn and Grass

Grass benefits from regular fertilizing throughout the growing season, as well as a boost of nutrients even when it is lying dormant during winter. There is all manner of specific nutrient ratios developed for lawns from 15-0-15 fertilizer through to 6-0-0, all have a specific purpose. But to give a continuous supply of balanced nutrients a 12-12-12 is a good option for most grasses from Bermuda, St Augustine, or Marathon. It provides many different benefits for helping to maintain turf, encouraging growth as well as keeping it looking good all year long. This includes:

  • Stimulating healthy root growth
  • Protecting against weather stresses
  • Improving durability so it is able to withstand wear and tear from footfall
  • Enhancing a vibrant and lush color to enhance its beauty and they benefit from the application of balanced fertilizers
  • Enriching soil that then becomes absorbed by the roots

How and When to Use 12-12-12 Fertilizer

Using a 12-12-12 fertilizer can be beneficial. But you have to use it carefully to provide the best benefits to your plants.

Always be sure to follow the manufacturer’s recommendations in order to get the best possible results from a triple 12 fertilizer. A reputable manufacturer will provide comprehensive directions for use either via their website or on the packaging. Make sure you are fully informed on how, when, and with what frequency you should apply it depending on what you want to fertilize. 

Let’s look at some general 12-12-12 fertilizer tips. 

Evergreen and Deciduous Trees and Shrubs

Trees and shrubs need feeding throughout the year. Some varieties need special attention, but an application of fertilizer at the beginning of the season and the end of it can usually sustain them pretty well. Consider liquid concentrates with a hose attachment for the easiest application to offer a quick release of nutrients or use fertilizer spikes or granules for a release of nutrients over a sustained period of time.

Blooming Annuals and Perennials

Flowers have a short period where they are on full display. Just prior to that, they need ample fertilization. But, they can also benefit from a steady supply of macronutrients in their soil at all stages of the growing seasons. And perennials need fertilization to prepare for the dormant season as well. 

Time-release granules are very effective for flower fertilizers. Remember to dead-head or remove any spent blooms once they are past their best. This will often encourage new growth and a second bloom.


Vegetable gardens need the most careful and focused application of different fertilizers. Unless you are only growing one vegetable, you’ll need to tailor your fertilizer nutrients and applications to their individual needs.

For instance, squash, tomatoes, cucumbers, and peppers are pretty heavy feeders, so you want to encourage strong root development early, then strong stem development, and finally big bloom and fruit production for high yields of your favorite veggies. And they need various ratios throughout the season – nitrogen to encourage initial foliage followed by potassium later in the season to encourage flowering and fruit production. 

Root vegetables, like carrots and radishes, can become inedible if their leafy growth above ground is over-stimulated at the expense of their underground development. No one prize radishes for their leaves, so make sure to encourage root development with phosphorus, and don’t overdo it with your nitrogen. 

But lettuces have very shallow roots and need plenty of nitrogen to develop our favorite leafy greens. 

Indoor plants

Since houseplants are often working at a deficit in terms of their soil’s nutrient quality, a balanced soil application before planting and a couple of times throughout the year in limited quantities is very helpful. 

Fertilizer spikes make doing so very easy without needing to perform multiple applications. Alternatively, use a liquid fertilizer and dilute it with water, then incorporate feeding into your plant’s normal watering schedule.

Different Lawn Types

For much of the year, lawns and grasses benefit from the application of balanced fertilizers.

Application Rate for Lawns

Most lawn fertilizers are granular and are best applied by a simple broadcast spreader. Your fertilizer will likely have instructions for how much to use based on the size of your lawn.

You’ll also often see a list of settings for some of the most common spreading machines available on the market, along with ratios of product needed versus lawn size. The distribution settings on your particular spreading machine will need to be adjusted accordingly to ensure even distribution across your lawn surface area.

How Often to Use 12-12-12 on Lawns

A good lawn needs fertilization coinciding with the beginning and end of the growing season at a minimum. 

Ideally, you should apply fertilizers to your lawn at all these times for a total of five or six applications:

  • Early Spring (consider adding weed preventatives as well)
  • Late Spring (consider supplemental weed-growth preventers)
  • Early Summer (add grub and insect control)
  • Summer 
  • Early Fall 
  • Late Fall

I always recommend monitoring the pH levels in your soil annually and investing in a soil test kit is always a worthwhile investment. Whilst lawns benefit from a balanced fertilizer, there will be occasions when the pH levels in your soil may need to be adjusted to compensate for any increase in acid or alkalinity. In this case, you will need to tailor your nutrient ratios to your lawn’s specific needs. 

Verdict: When is 12-12-12 Fertilizer Best

Using a 12-12-12 fertilizer is the perfect way to offer an even balance of macronutrients and can be used to successfully feed many different species of plants, trees, shrubs, flowers, and vegetables. Of course, using a triple 12 fertilizer will be most effective if your soil has the right pH balance, so it’s always a good idea to get this checked out before you begin planting.

Fertilizers with an N-P-K of 12-12-12 are usually multi-purpose and can be a cost-effective way to feed your garden. They also come in different formats, from liquid concentrates, powders, or granules to fertilizer spikes. The choice is down to the user in terms of affordability and ease of use.