When to Use 20-20-20 Fertilizer? | How to Use Triple 20

When starting a new garden border, vegetable bed, or laying new sod, your soil may not be as fertile as it could be. Rather, as fertile as it needs to be, for all those new plantings to not only survive but thrive.

If you’ve had the chance to cultivate your soil with well-aged compost and other organic compounds to increase its fertility, prior to planting, keep setting that amazing example!

If not, that’s perfectly ok. Getting assistance is as easy as reading on.

The nutrient ratio in a 20-20-20 fertilizer is pretty straightforward. 20% nitrogen, 20% phosphorus and 20% potassium. Which is twice as much of each as in a standard, balanced NPK of 10-10-10. Making it the perfect choice to revitalize tired and infertile soil.

Then, once a soil test kit confirms that your soil is up to par, a 20-20-20 fertilizer can easily be diluted down to a 10-10-10 for continued use on lawns, garden beds, and vegetables. Not to mention, houseplants.

Understanding 20-20-20 Fertilizer Labels?

With so many options out there, figuring out the best fertilizer may seem time-consuming. When all you want to do is improve your soil and grow healthy plants without breaking the bank. Good news! You can easily match an effective fertilizer to those goals by understanding the labels. 

Most fertilizer manufacturers will state how much nitrogen, phosphorus, and potassium (NPK) the product contains on the label. On the back, will be a list of all secondary ingredients and fillers (if any). Include trace elements like calcium, magnesium, and other micronutrients that support plant health.

With all this talk of N-P-Ks, you may still be wondering what it is. How do you decipher an NPK ratio? What do all those numbers mean for your plants?

N-P-K Ratio

Every fertilizer label reflects three numbers, separated by dashes. This is its N-P-K ratio, indicating its proportions of nitrogen, phosphorus, and potassium. As mentioned, a 20-20-20 NPK means 20% nitrogen, 20% phosphorus and 20% potassium. Every plant requires these three elements in order to thrive. Just in different proportions or NPK ratios, whether grown in fertile soil or not. 

Each of these macronutrients plays a vital role in cell formation, photosynthesis, nutrient distribution, and flower and fruit 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. This gives foliage its green color and ensures 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 sufficient 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 work at the cellular level. Contributing to the construction of those same proteins and enzymes that nitrogen uses to regulate water and nutrients.


Potassium is responsible for the circulation of water, nutrients, and photosynthesized food throughout your plants. It also activates those 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 and extreme heat and drought by helping them conserve moisture. And is especially effective in encouraging large, well-formed fruit on vining crops like tomatoes, squash, and melons.

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 extending 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

Most liquid concentrate fertilizers are used by applying a water-diluted mixture around the base of your plants. Some are formulated to also be used as a foliar spray.  Nutrients are then 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. And are usually quite economical. However, caution is recommended, as over-feeding is common and can lead to root burn.

Water Soluble Powder

Powder fertilizer options 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 in orchards or on farms but does require a bit more “by-hand” effort in smaller spaces. While these are some of the most economical, they do carry a risk of root burn if exact measurements are not followed.

Slow-Release Granules

Granules are a slow-release choice. Heavily concentrated, these provide consistent nourishment for up to nine months, with the first results showing in just a couple of weeks. They are also less likely to cause root burn and are considered more eco-friendly.

Granular fertilizers are applied by casting them evenly around the base trees, shrubs, and plants. Often, no watering is needed to activate the release of nutrients so there is less risk that the product will leach into nearby surfaces or groundwater. 

Fertilizer Spikes

Spikes are one of the most convenient to use, especially if you have a container garden. Pre-measured in various sizes, they’re easy to push into loamy soil.  And being slow-releasing, they run little risk of root burn.

Nutrients are released from the spikes by micro-organisms that naturally live in the soil. And carry the added benefit of stimulating an increased resistance to disease and pests. Unused portions can then be stored mess-free until needed.

What is Triple 20 Fertilizer Used For?

The intended use of a triple 20 fertilizer is primarily to increase plant success and fertility in poor soil. But, it’s also effective for use on plants grown in hanging baskets to accommodate for the heavy leaching that occurs.  

When used appropriately, a 20-20-20 NPK encourages vibrant foliage to ensure optimum photosynthesis. While providing maximum support for flower and fruit formation.

For in-ground plantings, a 20-20-20 NPK should only be used at full strength for a short time. Followed by either a diluted version or another NPK better suited to the needs of specific plants.

Being aware of the potency of such equally high NPK amounts will help you to determine what to use this on and how much.

Why Use a Balanced Fertilizer?

Many outdoor plants require more of one macronutrient than another. But, when planted in poor soil, the infusion of a balanced fertilizer will provide the kind of nutrient-rich environment that plants need for healthy growth. 

Indoor plants benefit from a balanced fertilizer due to more frequent watering and the inevitable leaching of vital nutrients from the soil. An equal NPK will keep the growing medium fertile enough to keep them happy.

How and When to Use 20-20-20 Fertilizer

Depending on your application type, a 20-20-20 fertilizer can be applied as a liquid when watering or by working slow-release granules into the soil. In some cases, fertilizer spikes can also be very effective. 

When planting new trees in nutrient-deficient soil, a handful of triple 20 granules can be added to the hole prior to planting. This will help roots get established more quickly and encourage new growth. 

In new garden beds, working granules into the top few inches of soil or watering with a water-soluble option, just after planting, will provide plants with a great start. 

With vegetables, applying a triple 20 NPK just after transplanting will promote an abundant harvest.

Trees and Shrubs

Newly planted evergreen trees and shrubs establish strong root systems and produce healthy form, color and size faster when offered a monthly dose of triple 20 fertilizer for a month or two after planting. Increased soil fertility will also help these large plants develop an effective resistance against extreme temperatures. And to conserve moisture in times of drought.

Once established, perennial evergreens typically don’t require any further fertilizing. But, if browning or loss of foliage occurs out of season, a good soil test should be conducted to reveal what nutrient is lacking and needs to be added to the soil.

Fruit Trees

Fruiting trees and shrubs typically need more of one macronutrient than another at different times. So a triple 20 may not be suitable for them, in the long term. This includes berries, stone fruits, and citrus.

But, if you’re planting these in poor soil, adding a handful of dry 20-20-20 granules into the planting hole in spring will help them get established quickly. And contribute to a bountiful harvest, come summer and fall.


Ornamentals need consistent access to nutrients in order to produce a lot of vivid, summer color. A triple 20 NPK can ensure this and help accelerate plant maturity in annuals. Resulting in buds and flowers appearing sooner.

Unless, they’re already growing in rich, fertile soil. In this case, a 10-10-10 fertilizer will better support a nice show of healthy stems, leaves, and blooms. This would apply to those grown in the ground, pots, or hanging baskets. Anything higher than a 10-10-10 in rich soil may force extra growth and blooms but at the expense of the plant, as a whole.

Vegetable Gardens

All vegetables require nitrogen, phosphorus, and potassium for root development, vigorous growth, and flowering. Some will do just fine with a balanced NPK. But, climbers like tomatoes, squash, and melons require higher amounts of phosphorus and potassium once buds set. Even those grown in pots will need a phosphorus-heavy tomato fertilizer or a fertilizer for pumpkins and squash to produce large and well-formed fruit. 

If you’re starting with poor soil, it’s often beneficial to start out with a 20-20-20 NPK after transplanting. But, once buds are set, less nitrogen is needed. Otherwise, you’ll have a lot of foliage and few flowers and fruit.


Just like outdoor varieties, your indoor plants and trees need the right ratio of nutrients to form strong roots and healthy foliage. Extra 20-20-20 fertilizer can be diluted down to a 10-10-10 to give your indoor greenery all the nutrients they need. 

Flowering plants like African violets, begonias, and bromeliads use phosphorus to form lots of lovely flowers. Nitrogen for vibrant foliage and potassium for circulation of nutrients and water. So, these do well with a 7-9-5 NPK.

When adding extra nutrients to houseplants, please do so with caution. Just as with outdoor plants, too much can overwhelm and kill your plant.

Lawn and Grass

Lawns and grasses utilize phosphorus to produce a thick, lush blanket of color and form with a robust root system. Yet, relying on higher levels of nitrogen to maintain a vibrant structure that’s also resistant to wear-and-tear, excessive heat, and drought.

Excessive amounts of any macronutrient on lawns and different grass types may end up causing root damage ultimately killing them. 

The easiest way to know what NPK your lawn needs is to do a soil test prior to starting any kind of fertilization schedule. You may get lucky and already have nice, fertile soil underneath.

20-20-20 Fertilizer FAQ’s