When To Use 12-4-8 Fertilizer | How To Use It

12-4-8 fertilizer is one of the most popular fertilizers for home and commercial gardeners, but like all fertilizers, it’s easy to misunderstand the intended use of a particular formulation. Here’s what you should know about buying and using this 12-4-8 fertilizer.

Understanding 12-4-8 Fertilizer Label

The most important part of 12-4-8’s label, aside from the usage directions, is the specific ratio information. Make sure to read the label in its entirety before use.

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N-P-K Ratio

The N-P-K ratio is the specific amount of nitrogen, phosphorus, and potassium in this product. Note that this ratio is a percentage, so only slightly less than a quarter of the product by weight is the main fertilizing component.


Nitrogen helps stimulate foliage growth throughout a plant. Lack of nitrogen, or nitrogen deficiency, often causes plants to appear yellow, withered, or weaker than they should. This is because nitrogen is a vital component of chlorophyll, a molecule that helps plants convert sunlight into energy.

Earth’s atmosphere is about 78% nitrogen, but plants need to get it from the soil and can’t use the nitrogen floating around in the air.


Phosphorus helps plants with their root systems and is essentially a key building block in converting energy from the sun into healthy plant growth.


Potassium supports plants’ overall health, especially in absorbing other nutrients. Even if different minerals are available, plants without enough potassium won’t absorb enough to remain healthy.

Potassium also plays a critical role in the production of fruit and flower yield.

12-4-8 Fertilizer Type

12-4-8 is available in four primary forms for gardeners.

Liquid Fertilizer

Liquid fertilizer is generally easy to apply and fast-acting, although it’s often less concentrated than other options. Sprays are a good choice for individual plants that require foliar treatments, in gardens where applying granules won’t work, and in other special situations.

However liquid fertilizer can wash away in heavy rainfall, so it may not be a good choice in wetter areas. Think of liquid fertilizer as a great option for nutrient boosts.

Slow-Release Granules

Slow-release or controlled release granules are an excellent way to distribute 12-4-8 over lawns and other large areas of the border. These have the added benefit of offering ongoing support for several months, making them an effective method of application.

Water Soluble Powder

Water-soluble powders are similar to liquid sprays, but you mix them yourself. These require a little more effort to use, but each container will make quite a lot of liquid. This is a good option if you need a lot of fertilizer, but it might be too much for casual gardeners.

Fertilizer Spikes

Fertilizer spikes are long-term sources of nutrients for plants. You can put these near almost any plant of appropriate size, and the plant will slowly absorb nutrients from the spike over time.

Spikes come in various sizes, and it’s vital to get the correct size for the plant you’re growing. Larger plants usually need the most substantial spikes, with trees benefitting from the biggest spikes. If possible, place spikes close to roots so plants can easily access them.

What is 12-4-8 Fertilizer Used For?

12-4-8 is an all-purpose fertilizer, so it’s suitable for most plants in most situations. However, there are a few cases where it’s particularly helpful.

Nutrient Deficiency

12-4-8 can help solve nutrient deficiencies. It includes the three most essential nutrients, and many mixes have other nutrients to help fill out the volume. Nitrogen and Potassium are especially important here because it helps the plant absorb the other nutrients and minerals.

Lawn and Grass

12-4-8 is also a good mix for lawns and other grassy areas. The nitrogen helps ensure your grass looks dark green, which is the color most people prefer. It can also help reduce the loss of nutrients to weeds and other pests.

Potassium and Phosphorus support healthy root growth improving the lawn’s ability to withstand drought and improving the grass density to hold off invasive weeds.

12-4-8 for Trees and Shrubs

12-4-8 works on most trees and similar plants, although you’ll need to get enough into the soil to support them. Fertilizing trees is more challenging than fertilizing yards, and it’s easy to get the amount wrong.

Spikes are best for young trees but are too much for shrubs. Quick-release fertilizers are better for mature trees and shrubs that need a burst of nutrients.

12-4-8 for Hydrangeas and Flowering Plants

Hydrangeas and other flowering plants with large blooms can benefit from 12-4-8. In this case, a slow-release formula once a year is usually enough for their needs.

If you plan to feed only through the flowering period then a high phosphorus fertilizer is preferable.

Vegetable Gardens

Vegetable gardens do well with 12-4-8 but remember that removing the veggies also takes a lot of the potassium and other nutrients out with them. The application rate depends on the product’s recommendations, but every three months while growing is appropriate for most gardens.

For high cropping fruit or vegetables, a balanced feed such as a 20-20-20 may be preferable whilst the vegetable plants are in bloom.


Houseplants can have varying schedules depending on the type of fertilizer you’re using. Stakes are helpful once or twice a year, but liquid sprays could see application once or twice a month. Consult the manufacturer’s recommendations for houseplants.

Also, consider a half-strength application for the first three fertilizing periods each year.

How and When to Use 12-4-8

The best time to use 12-4-8 fertilizer depends on what you’re doing with it. Here’s what you should know.

12-4-8 Application Rate

The best application rate for 12-4-8 is whatever the manufacturer puts on the label. Fertilizers have different application rates, so there’s no universal answer to this question. However, most fertilizers will suggest you apply them several times a year. Colder areas can skip fertilizing in winter, while warmer regions can fertilize year-round.

Can You Use Too Much 12-4-8 Fertilizer?

Yes. Like all fertilizers, it’s possible to use too much. This causes a phenomenon called fertilizer burn. Lawns will eventually heal on their own, but too much fertilizer can outright kill trees, shrubs, and houseplants. Never use more fertilizer than the directions say.

12-4-8 Fertilizer FAQs