15-15-15 fertilizer is not a good choice for most lawns. 15-15-15 has too much potassium to be healthy for grass. This excess potassium can inhibit your grass from pulling in nitrogen and other nutrients. 15-15-15 fertilizer also contains high levels of phosphorus, which established lawns don’t need. 32-0-4 fertilizer is a far better choice for your lawn. Instead, use 15-15-15 fertilizer for garden plants, such as flowers, fruits, and vegetables.
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What Does 15-15-15 Fertilizer Mean?
The 3 numbers on each bag of fertilizer refer to the percentage of nitrogen, phosphorus, and potassium in the fertilizer. This is commonly called the “NPK” rating of the fertilizer. The first number is the percentage of nitrogen, the second number is the percentage of phosphorus, and the third number is the percentage of potassium. So, 15-15-15 fertilizer is 15% nitrogen, 15% phosphorus, and 15% potassium.
- The 3 numbers on a fertilizer bag refer to the percentage of nitrogen, phosphorus, and potassium in the fertilizer.
- 15-15-15 fertilizer is 15% nitrogen, 15% phosphorus, and 15% potassium.
- 15-15-15 fertilizer has the same nutrient ratio as 5-5-5 or 10-10-10, just in higher quantities.
Fertilizer NPK is best thought of as a ratio. Since 15-15-15 fertilizer contains equal amounts of the 3 main ingredients, it has a fertilizer ratio of 1:1:1. This is the same ratio as 5-5-5 fertilizer. You simply have to triple the amount of 5-5-5 fertilizer you use to get the same results as 15-15-15 fertilizer.
Why Are the numbers on Fertilizer Bags Important?
It’s essential to pay close attention to the numbers on the fertilizer you select because each essential nutrient in fertilizer has a different purpose. Here’s a quick breakdown of the 3 main ingredients in fertilizer:
- Nitrogen: Drives leaf and stem growth. For lawns, it encourages green color.
- Phosphorus: Encourages strong root growth. This makes it most important for new lawns.
- Potassium: Increases the drought-tolerance and disease-resistance of grass. In non-grassy plants, potassium is integral to flower and fruit development.
Fertilizers also contain other ingredients. Micronutrients such as iron are not listed in the NPK number, but encourage greener grass. So, it’s essential to pay close attention to the numbers on the bag, but there are other factors that make for an excellent fertilizer.
What is Triple 15 Fertilizer Used For?
“Triple 15” or 15-15-15 fertilizer is mostly used for gardens and crops. A fertilizer formula with a 1:1:1 ratio is a great multi-use fertilizer that provides a boost to almost all vegetables, fruits, and ornamental flowers. It’s great to have a balanced fertilizer on hand to make your flowers and veggies flourish.
- The most common use of 15-15-15 fertilizer is for fruits, vegetables, and flowering plants.
- Balanced fertilizers are great for gardens but not good for lawns.
- Lawn grasses require higher nitrogen content than 15-15-15, and lower potassium content.
- The improper balance of nutrients in 15-15-15 can harm your lawn.
15-15-15 fertilizer is not ideal for lawns or trees. Lawn grasses are typically either hungry for nitrogen or in need of phosphorus, depending on their stage of life. Additionally, most lawn grasses need relatively little potassium in comparison to nitrogen. So, a 15-15-15 fertilizer typically has much more potassium than your lawn needs. An excess of nitrogen can actually inhibit your lawn from pulling nutrients from the soil, making it fade and wilt. So, it’s not a good idea to use 15-15-15 fertilizer for most lawns.
What is the Best Fertilizer Ratio for Lawns?
The ideal fertilizer ratio for established lawns is high in nitrogen, contains little or no phosphorus, and has a small amount of potassium. For instance, a ratio of 32-0-4 is great for mature grass that has not been planted from seed or sod this year. This fertilizer contains 32% nitrogen, 0% phosphorus, and 4% potassium. It’s essential to use a low-phosphorus fertilizer when possible because excess phosphorus can pollute local water supplies.
- Use this 32-0-4 fertilizer if your lawn is more than 1 year old.
- Established lawns thrive when they are provided with high nitrogen content, little or no phosphorus, and low potassium levels.
- Spread this 22-23-4 lawn starter fertilizer if your lawn is less than 1 year old.
- New lawns need high nitrogen and phosphorus with just a small amount of potassium.
- Works to feed and strengthen your lawn.
- Helps your lawn absorb and use water and nutrients better.
- You can use this fertilizer on any grass type.
If your lawn is new, choose a fertilizer that has roughly equal nitrogen and phosphorus content with a small amount of potassium. A good lawn starter fertilizer has a 22-23-4 NPK balance. The higher quantity of phosphorus helps your new seed or sod establish healthy roots in its first growing season. The low potassium content ensures that the grass will pull in the nitrogen and phosphorus in the fertilizer. A higher potassium content could prevent your grass from accessing these essential nutrients.
- Great starter fertilizer for new seed or sod.
- You can also use Pennington UltraGreen for overseeding or on an existing lawn.
- 5% Iron promotes a deep, thick, lush lawn.
What Number on Fertilizer Makes Grass Green?
The first number on lawn fertilizer bags is most associated with a green lawn. This first number signifies the nitrogen content. So, in a 32-0-4 fertilizer, the 32 means the fertilizer is 32% nitrogen. Nitrogen promotes green grass blade and stem growth. Without adequate nitrogen, your grass will struggle to turn green. However, some ingredients in fertilizer help green up your grass but are not listed in the bag number. Iron, for example, is essential for green grass but is found only on the fine print of most fertilizer labels.
- Nitrogen—represented by the first number on a fertilizer bag—is the most essential ingredient for grass growth.
- Fertilizers with high iron content also help grass turn rich, dark green.
- High potassium levels can prevent your grass from absorbing nitrogen from fertilizer.
- The nitrogen content in lawn fertilizer should be 5–10 times higher than the potassium content.
A high nitrogen content does not always mean the fertilizer is good for grass. If both the nitrogen and potassium content are high, the excess potassium will prevent your grass from pulling in nitrogen. Nitrogen is signified by the first number on the fertilizer bag. Potassium is signified by the last number. So, 32-0-4 fertilizer is 32% nitrogen and 4% potassium. For lawns, choose a fertilizer that has 5–10 times more nitrogen than potassium.
Is Triple 15 Fertilizer Good for Grass?
You should not use 15-15-15 fertilizer for your lawn. The reasons for this are:
- 15-15-15 fertilizer contains equal amounts of nitrogen, phosphorus, and potassium.
- Established lawns thrive on fertilizer with high amounts of nitrogen, no phosphorus, and very little potassium.
- New lawns require equal amounts of nitrogen and phosphorus, but very small amounts of potassium.
- The excess potassium in 15-15-15 fertilizer can inhibit your lawn from pulling in soil nutrients.
- Choose a fertilizer with lower potassium for your lawn (symbolized by the third number on the fertilizer bag).
- 15-15-15 is best used for garden vegetables, fruits, and flowers.
The best types of fertilizers for rapid growth of your lawn and green color have much higher nitrogen content and much lower potassium content than 15-15-15 fertilizer. So, use 15-15-15 only for your garden. Choose a fertilizer engineered for grass when feeding your lawn.