When to Use 5-10-10 Fertilizer | How to Use It

If you’re a fan of growing tomatoes, squash, and melons, then you may also be a fan of a 5-10-10 fertilizer. If not, you might soon become one. 

Out of all the different NPK formulas available, the 5-10-10 ratio that can be found in fertilizers for Pumpkins, Squash, And Watermelons is one that safely carries your vining vegetables all the way to the finish line with large, well-formed fruit.

With double the amount of phosphorus and potassium than nitrogen, this particular ratio adjusts a plant’s focus from forming healthy foliage to the formation of buds, flowers, and fruit.   

Of course, vibrant foliage will still be supported with the help of the 5% nitrogen. But, any more than that the focus will remain on creating foliage. With few flowers and fruit, if any.

When growing these vegetable varieties in less-than-desirable soil, a triple 10 NPK fertilizer might be more appropriate to increase nutrient availability. Then, when buds set on your vining veggies, a few extra organic compounds can be worked in to increase phosphorus and potassium levels.

Understanding 5-10-10 Fertilizer Labels?

5-10-10 Fertilizer

Trying to figure out if a 5-10-10 NPK is the best one for you, may seem daunting. When all you want to do is to grow healthy plants without spending a fortune. Well, you’ve come to the right place! You can easily match an effective fertilizer to your specific plant goals by understanding the fertilizer labels. 

Most manufacturers will state the NPK ratio of their product on the label. Which will reflect how much nitrogen, phosphorus, and potassium the product contains. On the back of the container should be an ingredients list, just like you’ll find on grocery store items.

This list reveals all the ingredients that make up that product. First, the NPK content (macronutrients), then all secondary micronutrients like calcium and magnesium. Followed by trace elements such as copper and manganese. Lastly, will be any fillers the manufacturer may include, for an easy-to-use product.

N-P-K Ratio

So, how exactly do you decipher an NPK ratio? If you’re not familiar, an NPK ratio is three numbers, separated by dashes. This indicates the fertilizer’s nitrogen, phosphorus and potassium content.

A 5-10-10 NPK means 5% nitrogen, 10% phosphorus and 10% potassium. Every plant requires these three macronutrients in order to thrive. Just in different proportions or NPK ratios.

Each of these macronutrients plays a vital role in cell formation, photosynthesis, and flower production. All working in tandem to create a healthy, bountiful plant. And when applied properly, they can increase soil fertility and beneficial bacteria activity, too.


Nitrogen plays a vital role in encouraging the growth of healthy foliage, by fueling the production of chlorophyll. These cells give foliage its green color and ensure that photosynthesized energy is available to convert starches and carbohydrates into food. 

This multi-tasking macronutrient also fuels the proteins and enzymes that regulate water and nutrient uptake and disbursement. High nitrogen fertilizer is typically formulated for lawns and other plants where foliage is the primary focus.


Phosphorus is key in the process of photosynthesis. Once the chlorophyll is produced, this macronutrient triggers the energy captured by the chlorophyll to convert starches and carbohydrates into food. Another important (and more visible) function of phosphorus is the creation of abundant flowers and fruit, rather than foliage. 

Phosphorus begins its critical work at the cellular level. Contributing to the construction of those same proteins and enzymes that nitrogen uses to regulate water and nutrients. High phosphorus fertilizers are typically used for flowering annuals or winter greens. However, in the main specialist phosphorus fertilizers are seldomly used other than in commercial application, due to the high level of natural phosphates in garden soil.


Potassium is responsible for the circulation of water, nutrients, and photosynthesized food throughout plants. It also activates the same proteins and enzymes that were formed using phosphorus and nitrogen to build a healthy plant structure. 

Proper amounts of potassium contribute to a plant’s resistance against disease extreme heat and drought by helping them to conserve moisture. This macronutrient is especially effective in squash, melon, and tomato fertilizers because it encourages tasty, vibrantly colored fruit on these vining crops.

Fertilizer Type

There are several application types available that make the process of nourishing your plants and soil less strenuous and more enjoyable. These fall into four different categories: 

  • Quick Release – these liquid or water-soluble options offer an immediate uptake of nutrients. Resulting in accelerated improvement for plants growing in poor soil.
  • Slow-Release – Heavily concentrated, these offer a steady stream of nutrients over an extended period of time. Rather than inundating plants with high doses all at once. 
  • Organic – made from strictly natural materials like well-rotted plant material and animal bi-products that contain beneficial levels of nitrogen, phosphorus and potassium.
  • Inorganic – manufactured with minerals and synthetic chemicals. These can result in a higher yield. But, they can also potentially contaminate soil and nearby water sources.

Liquid Concentrate

Liquid concentrates are used by mixing in a recommended amount of water and applying it around the base of plants. Some are also formulated to be used as foliar sprays and are quite effective when leaves show signs of nutrient deficiency. 

Premixed options are available, as well. But, maybe a bit higher in price. Once applied, nutrients are immediately carried to the root system through the soil or leaves.

Liquid feeds tend to keep the pH levels in your soil balanced, as well. However, caution is recommended, as over-feeding is common and could lead to root burn.

Water Soluble Powder

Water-soluble, powder fertilizers can be applied either directly into the soil around the base of trees, shrubs, and plants or diluted in water as a “tea”. This type is perfect for larger applications such as expansive allotments or home vegetable gardens.

As a dissolvable, the effectiveness per application is fairly consistent. As nutrients are equally dispersed throughout the solution when mixed with water. 

Powder fertilizers are some of the most economical and carry the benefit of virtually indefinite shelf life. But they do carry a risk of root burn if exact measurements and manufacturer’s instructions are not followed.

Slow-Release Granules

Granules are a slow-release choice. Heavily concentrated, these can provide consistent nourishment for up to nine months, with the first results showing in just a couple of weeks.

They’re also less likely to cause root burn and are considered more eco-friendly. Since no watering is needed to activate and are less likely to leach into nearby water sources. 

Granular fertilizers are applied by casting them evenly around the base of trees, shrubs, and plants. They can safely feed crops longer into the growing season and support even growth on lawns, while reducing the amount of fertilizer required, per season.

Fertilizer Spikes

Spikes are one of the most convenient to use, especially if you have a substantial container garden. Pre-measured in various sizes, they’re easy to push into loamy soil.

In compacted soil under large trees, simply water the area to be fertilized first. Then, gently tap spikes into softened soil with a rubber mallet.

This form of nutrients, released by micro-organisms that naturally live in the soil, carries the added benefit of stimulating an increased resistance to disease and pests.

And being slow-releasing, they run little risk of root burn. Unused portions can then be stored mess-free until needed.

What is a 5-10-10 Fertilizer Used For?

If you’re looking for one fertilizer to use in your garden throughout the growing season, a 5-10-10 ratio will promote healthy, robust plants. With a little extra phosphorus and potassium for flowering ornamentals, fruiting shrubs, and vegetables.

If you grow your crops and flowers from seed, however, I do suggest starting with an NPK that’s a bit higher in nitrogen, like a 10-10-10 or even a 20-20-20 fertilizer. Plants need more nitrogen, in the beginning, stages of growth, to generate strong root systems and foliage that will carry the plant through to maturity. 

Once buds are set, a switch to a 5-10-10 NPK will encourage more blooms and fruit, rather than just more foliage. This progression should apply to new houseplant cuttings, as well. 

Trees and Shrubs

Typically, non-flowering evergreen trees and shrubs rarely need fertilizing, after a few years of getting established. But, if they begin to show signs of deficiency, an NPK higher in nitrogen will help to trigger new, healthy growth. 

For flowering varieties, like magnolia, wisteria, hydrangea, and azalea, a fertilizer higher in phosphorus and potassium (like a 5-10-10) can be introduced if a growing season goes by with few flowers. 

Luckily, there are some low-nitrogen options that are formulated to increase or maintain soil acidity, too. This will even further benefit acid-loving plants and can be used as a fertilizer for azaleas, hydrangeas, berry shrubs, and flowering trees such as Crape Myrtle.

Fruit Trees

Fruiting trees and shrubs, including citrus, will need more of one macronutrient than another and at different times. A 5-10-10 works very well toward abundant flowers and fruit. While providing just enough nitrogen for lush, green foliage.

This is especially true for smaller species when a fertilizer for fruit trees grown in pots is required. To offset the heavy leaching of water and nutrients that occurs in pots, a consistent application of a 5-10-10 NPK will maintain steady nutrient access.

Dahlias and Other Flowers

Flowering is an essential step in a plant’s reproductive process. The increased phosphorus in a 5-10-10 NPK stimulates healthy bud production. Followed by flowers and viable seed formation.

Bulbs and tubers, like dahlias, experience accelerated plant maturity, resulting in buds and flowers appearing sooner, for lots of brilliant, seasonal colors. 

The higher potassium content in a 5-10-10 NPK that is often found in fertilizers for Dahlias will not only boost drought tolerance and disease resistance in these flowering plants but also enhance crop color.

Vegetable Gardens

All vegetables require nitrogen, phosphorus, and potassium for root development, vigorous growth, and flowering. And some will do just fine with a balanced NPK, such as a 10-10-10. 

But, applying a 5-10-10 NPK fertilizer, just as buds set, make tomatoes juicier and more vibrant in color. Specific fertilizers for Cucumbers and zucchini will produce tasty, plentiful crops and more seeds for the following year. And watermelon, cantaloupe, and honeydew will be ripe for creating happy memories of summer.


Houseplants grown in fertile soil may not need as much nitrogen to maintain strong roots and healthy foliage. But, due to frequent leaching of water and nutrients, they’ll need a consistent stream of good quality houseplant fertilizer. A 5-10-10 NPK will provide what most houseplant varieties need.

An exception would be flowering houseplants like African violets and bromeliads. Which need more phosphorus to form flowers and nitrogen for vibrant foliage. These perform far better with a 7-9-5 NPK.

Lawn and Grass

Phosphorus produces thick blankets of color with robust root systems in lawns and grasses. Yet, relying on nitrogen to maintain a vibrant structure that’s also resistant to wear-and-tear, excessive heat, and drought.

Unless a soil test has revealed high nitrogen content, a 5-10-10 fertilizer may not provide enough. If it has, this low-nitrogen ratio will prevent burning and root damage. If not, a slightly higher nitrogen option may be a better choice.

How and When to Use 5-10-10 Fertilizer

When you’re in need of less nitrogen to prevent excessive foliage growth and need more prosperity and potassium to promote bud and flower development, a 5-10-10 fertilizer is the one to reach for. 

The relatively low percentage NPK will provide those plants that require just a small boost of nutrients to flourish and will also reduce any risk of root and leaf burn. 

A triple 6 fertilizer will also support color and flavor in leafy vegetables like broccoli and cabbage, grown in fertile soil. As well as kale, celery, and asparagus. Especially when these are planted in soil that just needs a small boost in nutrients. 

Can You Use Too Much 5-10-10 Fertilizer?

Too much phosphorus, potassium, or nitrogen can harm plants. Over-fertilization can weaken plants and leave them vulnerable to pests and diseases. Signs of overfeeding include stunted growth, browning, or yellowing of leaves and bud drop.

When in doubt, a soil test will determine what nutrients are already present. Then, compare those results with the needs of what you’re growing. The difference will be what you need to add. 

5-10-10 Fertilizer FAQ’s