The Numbers on a Fertilizer Bag: What do they mean?

Imagine navigating the aisles of your local garden center, determined to give your lawn the care it deserves. As your gaze falls upon bags of fertilizer, adorned with three mysterious numbers, a realization hits you: understanding these numbers is key to unlocking the secret to a lush, green lawn. In this blog post, we’ll demystify the three numbers on a fertilizer bag, focusing on the Southern Ontario perspective where phosphorous levels are naturally sufficient in most soils. Plus, we’ll delve into the importance of minimizing phosphorous use to safeguard our groundwater, rivers, and lakes. 

The Power Trio: Nitrogen (N), Phosphorous (P), and Potassium (K)

Let’s cut to the chase and explore how the superhero trio of Nitrogen (N), Phosphorous (P), and Potassium (K) influences your lawn. These three numbers are the key to understanding the nutrient balance your grass needs for optimal health.

  • Nitrogen (N) – The Energizer Bunny

Nitrogen takes the spotlight as the energy boost your lawn craves. Represented by the first number on your fertilizer bag (e.g., 20-10-10), a higher nitrogen content fuels lush, vigorous growth, and that coveted vibrant green hue. Think of it as a refreshing espresso for your grass, ensuring it wakes up invigorated and ready to face the day.

  • Phosphorous (P) – The Foundation Builder

In Southern Ontario, where most soils naturally contain sufficient phosphorous, the second number on your fertilizer bag (e.g., 10-20-10) takes a backstage role. However, phosphorous remains crucial for strong root development, disease resistance, and overall plant resilience. Picture it as the silent hero working underground, fortifying your grass from the roots up.

  • Potassium (K) – The All-Rounder

The third number on your fertilizer bag (e.g., 10-10-20) represents potassium, the versatile nutrient contributing to overall plant health. While potassium might not steal the spotlight, it’s the Swiss Army knife of nutrients, enhancing your lawn’s resistance to diseases, stress, and environmental challenges. It ensures your grass remains resilient, adapting to varying conditions with ease.

Choosing Sustainable Fertilizers for Southern Ontario

Given that Southern Ontario soils are naturally sufficient in phosphorous, it’s crucial to adopt a sustainable approach to fertilizing. Here’s how you can make environmentally conscious choices:

  • Balance is Key: Opt for balanced fertilizers (e.g., 20-10-10) for general-purpose use. These formulations provide a well-rounded mix of nutrients without overloading your lawn with unnecessary phosphorous.
  • Low Phosphorous Formulas: When selecting fertilizers, especially outside of seeding, prioritize those with lower phosphorous content (e.g., 20-0-10). This ensures your lawn receives the necessary nutrients without contributing to pollution concerns.
  • Consider Soil Tests: Conduct soil tests periodically to gauge the nutrient levels in your lawn. This information helps tailor your fertilizer choices to your specific soil conditions, preventing overapplication of phosphorous.

Southern Ontario’s Call to Action: Minimizing Phosphorous for a Greener Tomorrow

In Southern Ontario, our commitment to preserving the environment extends beyond our homes. By minimizing phosphorous use in lawn care, we contribute to safeguarding our groundwater, rivers, and lakes. Sustainable choices today ensure a healthier, greener tomorrow.

Call to Action: Discover GroGreen Lawn Care

For Southern Ontario homeowners committed to sustainable lawn care, GroGreen Lawn Care is your trusted ally. Our expert technicians understand the unique needs of Southern Ontario lawns and employ environmentally responsible practices. From customized fertilization plans to weed control and pest management, GroGreen prioritizes both the health of your lawn and the well-being of our environment. Join us in creating a greener Southern Ontario – visit GroGreen Lawn Care and embark on a journey to a thriving, eco-friendly lawn today.


Armed with the knowledge of those three numbers on your fertilizer bag, you’re now empowered to make informed choices for your Southern Ontario lawn. In a region where phosphorous levels are naturally sufficient, adopting a sustainable approach to fertilizing is not just a choice – it’s a responsibility. By striking the right balance and minimizing phosphorous use, you contribute to the preservation of our precious water resources.

So, the next time you’re in the garden center, confidently choose a fertilizer that aligns with the needs of your Southern Ontario lawn. With the superhero trio and a commitment to sustainability, your grass will not only thrive but also contribute to the beauty and health of our beloved region. And remember, with GroGreen Lawn Care by your side, the journey to a lush, eco-friendly lawn is just a click away.