19-19-19 or “triple 19” fertilizer is a common, all-purpose garden fertilizer that can be used in a variety of applications, but it is not the best fertilizer for your lawn. You are better off using a high-nitrogen fertilizer on established lawns and a high-phosphorus “lawn starter” fertilizer on new sod lawns and seedlings.
It’s not that 19-19-19 will harm your lawn, it’s just that it’s better used on vegetables and garden plants. You can boost grass growth more efficiently and cheaply by using specialized lawn fertilizers.
What Does “19-19-19” Mean?
The numbers (19-19-19) indicate the Nitrogen, Phosphorus, and Potassium percentages in the bag of fertilizer. A bag of 19-19-19 contains 19% Nitrogen, 19% Phosphorous, and 19% Potassium, by weight.
- The first number is Nitrogen content. This promotes grass blade growth.
- The second number is Phosphorus content. It encourages young grass to form roots.
- The third number is Potassium content. This nutrient helps grass resist disease.
The numbers on a bag of fertilizer always signify Nitrogen, Phosphorus, and Potassium percentages in that order. This is often referred to as the NPK number (K symbolizes Potassium on the periodic table).
Reading Fertilizer Nutrient Ratios
It’s helpful to think of the NPK number as a ratio. If you have a bag of 20-20-20 fertilizer and 10-10-10 fertilizer, they both have a nutrient ratio of 1:1:1. If both bags weigh 100 pounds, then there are 20 pounds of each nutrient in the 20-20-20 bag and 10 pounds of each nutrient in the 10-10-10 bag.
- 19-19-19 is a ratio of Nitrogen, Phosphorus, and Potassium in the fertilizer.
- 19-19-19 has a 1:1:1 ratio.
- 10-10-10 fertilizer also has a 1:1:1 ratio.
- 20-10-10 has a 2:1:1 ratio.
Keep this ratio in mind when shopping for fertilizer. The ratio is more important than the numbers themselves. You would deliver the same amount of nutrients by spreading 2 bags of 10-10-10 fertilizer in an area as you would by spreading 1 bag of 20-20-20.
What is the Best NPK for Lawn Fertilizer?
Turfgrasses have specialized needs. 19-19-19 is great for garden plants because the high phosphorus content helps form fruits and flowers. Grass doesn’t produce fruits and flowers, so it really only needs phosphorus when it is young because this nutrient helps new grass establish roots.
- Lawn fertilizers are typically higher in Nitrogen than any other nutrient.
- Phosphorus is needed mostly in lawn starter fertilizers.
- Potassium is required for grass in small amounts compared to Nitrogen.
Lawns thrive on Nitrogen. If you want thick, lush green grass, you want a fertilizer that has a much higher Nitrogen content compared to the other nutrients. For instance, some lawn fertilizers have an NPK of 32-0-4. This means it has 32% Nitrogen, no Phosphorus, and 4% Potassium.
Best Fertilizer NPK for New Lawns
Whether you’re establishing a new lawn from seed or sod, your lawn needs a starter fertilizer. Ideally, the second number (indicating Phosphorus) should be the highest number in a lawn starter fertilizer NPK. The first number (Nitrogen) should be a bit lower than the second. The third number (Potassium) should be the lowest of all.
- Should have a Nitrogen content slightly lower than the Phosphorus content.
- The Phosphorus content should be the highest of the 3 nutrients.
- Requires little to no Potassium. The third number should be the smallest.
- This 24-25-4 Fertilizer is perfect for new lawns.
By providing slightly more Phosphorus than Nitrogen to a new lawn, you encourage the grass to prioritize new root development, allowing it to establish itself more quickly, creating a much healthier lawn in the long term.
Best Fertilizer NPK for Established Lawns
Once your lawn is established, meaning it’s mature enough that you’ve mowed it 3–4 times, it no longer needs starter fertilizer. Established lawns thrive on Nitrogen, so the first number in the NPK ratio should be the highest by far. The second number (Phosphorus) should be the lowest because the grass has already established roots. The third number (Potassium) should be less than half the Nitrogen content.
- Thrives on high-Nitrogen fertilizers, which encourage aboveground growth.
- Has low or no Phosphorus needs.
- Needs a small percentage of Potassium, to help in disease, drought, and cold resistance.
- For northern lawns planted with cool-season grass, use a 32-0-4 fertilizer.
- For southern lawns planted with warm-season grass, apply 34-4-10 fertilizer.
It’s important to provide additional Potassium to warm-season grasses because this nutrient helps grass resist drought that rarely impacts northern regions. As always, give your established lawn Nitrogen first and foremost.
Is Triple 19 Fertilizer Good for Lawns?
Use triple 19 fertilizer in gardens for fruits, vegetables, and flowers. It is not ideal for lawns, which require fertilizers with much higher Phosphorus content when they’re young and much higher Nitrogen content when the grass is mature. 19-19-19 fertilizer simply doesn’t deliver the right balance of nutrients. You’ll use far more 19-19-19 fertilizer trying to achieve the same results you’d get with a fertilizer engineered for grass.
However, it’s better to use a suboptimal fertilizer than no fertilizer at all. If you have some 19-19-19 fertilizer laying around, it won’t harm your yard if it is applied at the right time in a lawn fertilization schedule and spread at product label rates. If you’re going out in search of fertilizer for your lawn, however, there are options on the market that are much better than triple 19 fertilizer.