A thick, vibrant lawn doesn’t just happen by chance. It starts with strong roots that anchor the grass, soak up nutrients, and withstand drought, pests, and heavy foot traffic. Choosing the right fertilizer for grass root growth lays the foundation for a lawn that’s not only beautiful but also tough and low-maintenance. After hours of research, hands-on testing, and digging into customer feedback, I’ve rounded up the top five fertilizers that excel at promoting deep, healthy root systems. Whether you’re starting a new lawn, reviving a patchy one, or simply aiming for greener grass, these products deliver results.
In this guide, I’ll break down each fertilizer’s strengths, how it works, and why it stands out. From granular blends to liquid sprays, there’s something here for every lawn type and care routine. Let’s dive in and explore the best options to give your grass the root strength it deserves.
Contents
- Why Root Growth Matters for Your Lawn
- 1. Scotts Turf Builder Lawn Food – Fertilizer for All Grass Types, 5,000 sq. ft., 12.5 lbs.
- 2. Scotts Liquid Turf Builder Lawn Fertilizer for All Grass Types, 32 fl. oz.
- 3. 0-0-1 RGS Root Growth Bio-Stimulant, Sea Kelp | N-Ext
- 4. Fertilome (10650) Root Stimulator & Plant Starter Solution 4-10-3 (1 gal)
- 5. Ultimate 3-18-18 NPK Lawn Food Liquid Fertilizer by Simple Lawn Solutions
- How to Choose the Best Fertilizer for Grass Root Growth
- Tips for Maximizing Root Growth
- Comparing the Top 5 Fertilizers
- Final Thoughts
- Frequently Asked Questions
Why Root Growth Matters for Your Lawn
Before we get to the products, let’s talk about why root growth is the backbone of a healthy lawn. Strong roots act like an underground support system. They dig deep into the soil, pulling in water and nutrients even during dry spells. This makes your grass more resilient to heat, drought, and wear from kids or pets running around. Deep roots also crowd out weeds naturally, reducing the need for herbicides. A fertilizer designed for root growth typically includes key nutrients like phosphorus for root development, potassium for stress resistance, and sometimes nitrogen for balanced top growth. Bio-stimulants, like sea kelp or humic acid, can also supercharge root vigor by improving soil health and nutrient uptake.
Now, let’s jump into the top five fertilizers that can transform your lawn’s root system.
1. Scotts Turf Builder Lawn Food – Fertilizer for All Grass Types, 5,000 sq. ft., 12.5 lbs.
Scotts is a household name in lawn care, and their Turf Builder Lawn Food lives up to the hype. This granular fertilizer, with an NPK ratio of 32-0-4, is a powerhouse for promoting strong roots across all grass types. It’s designed for established lawns, but its high nitrogen content and potassium boost make it a solid choice for encouraging deeper root systems.
What Makes It Stand Out
This fertilizer shines for its versatility. Whether you have Bermuda, fescue, or Kentucky bluegrass, it delivers consistent results. The 32% nitrogen fuels lush, green growth above ground, while the 4% potassium strengthens roots to handle drought and foot traffic. Its All-in-One Particle technology ensures even nutrient distribution, so you don’t end up with patchy spots. One 12.5-pound bag covers 5,000 square feet, making it ideal for medium-sized lawns.
How to Use It
Spread it evenly using a Scotts broadcast or rotary spreader set to 3 ¼ for optimal coverage. Apply it to a dry lawn, then water lightly to help the granules soak in. You can use it any time during the growing season, but spring and fall applications work best for root development. For maximum impact, aerate your lawn first to let the nutrients reach the roots more easily.
Pros
- Works on all grass types, from cool-season to warm-season.
- High nitrogen promotes vibrant green blades.
- Potassium strengthens roots for drought and stress resistance.
- Covers 5,000 square feet with one bag.
- Easy to apply with a spreader for even results.
Cons
- No phosphorus, so it’s not ideal for brand-new lawns needing root establishment.
- Granular form requires a spreader for best results.
- May need frequent applications (every 6-8 weeks) for sustained growth.
Who It’s For
This is perfect for homeowners with established lawns looking to boost root strength and overall turf health. If you want a low-fuss, reliable fertilizer that delivers greener grass and deeper roots, this is a top pick.
2. Scotts Liquid Turf Builder Lawn Fertilizer for All Grass Types, 32 fl. oz.
If you prefer the ease of a liquid fertilizer, Scotts Liquid Turf Builder is a game-changer. This 32-ounce bottle connects directly to your garden hose, feeding and watering your lawn in one step. With an NPK of 29-0-2, it’s formulated to green up grass fast while supporting root vigor.
What Makes It Stand Out
Speed and convenience set this product apart. The liquid formula absorbs quickly through grass blades and roots, delivering visible greening in as little as three days. While it’s light on potassium (2%), the high nitrogen content drives top growth, and the fast-acting nature ensures roots get a quick nutrient hit. It’s safe for all grass types and covers up to 6,000 square feet, making it a great choice for larger lawns.
How to Use It
Attach the bottle to a garden hose and spray evenly across your lawn. No mixing or measuring required—just point and spray. Apply it during active growing seasons, like spring or early summer, for best results. Watering isn’t necessary since the formula includes moisture, but keep your lawn moist for a few days after to maximize nutrient uptake.
Pros
- Super easy to apply with a hose-end sprayer.
- Fast results, with greener grass in days.
- Covers up to 6,000 square feet.
- Safe for all grass types.
- No spreader needed, saving time and effort.
Cons
- Low potassium limits long-term root strength.
- Liquid formula may require more frequent applications (every 4-6 weeks).
- Not ideal for new lawns needing phosphorus.
Who It’s For
Busy homeowners who want quick results without the hassle of granular fertilizers will love this. It’s ideal for established lawns needing a fast green-up and moderate root support.
3. 0-0-1 RGS Root Growth Bio-Stimulant, Sea Kelp | N-Ext
For those leaning toward organic or eco-friendly options, N-Ext’s 0-0-1 RGS Root Growth Bio-Stimulant is a standout. This liquid concentrate, made with sea kelp and humic acid, focuses on soil health and root development rather than traditional NPK nutrients. It’s designed to work alongside other fertilizers, supercharging their effects.
What Makes It Stand Out
This bio-stimulant is all about roots. The sea kelp provides natural growth hormones that stimulate root elongation, while humic acid improves soil structure and nutrient absorption. With a low NPK of 0-0-1, it’s not about top growth—it’s about building a robust root system that supports long-term lawn health. It’s safe for all grass types and can be used year-round, even on stressed or recovering lawns.
How to Use It
Mix 3-6 ounces of the concentrate with a gallon of water in a pump sprayer and apply evenly across 1,000 square feet. For best results, use it every 2-4 weeks during the growing season. Pair it with a balanced fertilizer like Scotts Turf Builder for a one-two punch of root and top growth.
Pros
- Organic ingredients promote sustainable lawn care.
- Boosts root growth and soil health with sea kelp and humic acid.
- Enhances the effectiveness of other fertilizers.
- Safe for all grass types and seasons.
- Easy to apply with a pump sprayer.
Cons
- Requires a separate sprayer for application.
- Low NPK means it’s not a standalone fertilizer.
- Smaller coverage area per bottle compared to granular options.
Who It’s For
Eco-conscious gardeners or those with stressed lawns will find this bio-stimulant a perfect addition to their routine. It’s best for boosting root growth alongside a primary fertilizer.
4. Fertilome (10650) Root Stimulator & Plant Starter Solution 4-10-3 (1 gal)
Fertilome’s Root Stimulator is a liquid fertilizer tailored for new grass, transplants, or lawns needing a root boost. With an NPK of 4-10-3, it’s packed with phosphorus to drive root development, making it a go-to for establishing strong foundations in young or struggling turf.
What Makes It Stand Out
This product excels at kickstarting root growth. The 10% phosphorus is higher than most fertilizers, directly targeting root establishment for new seeds, sod, or plugs. It also includes indole-3-butyric acid, a plant hormone that encourages root formation. The 4% nitrogen supports moderate top growth, while 3% potassium aids stress resistance. One gallon covers multiple applications, offering great value for larger projects.
How to Use It
Dilute 3.5 ounces of the solution in a gallon of water and apply to the root zone of new grass or transplants. For seeding, apply after planting and repeat every 2-3 weeks for the first month. Use a watering can or sprayer for precise application. Keep the soil moist to help the nutrients penetrate.
Pros
- High phosphorus promotes rapid root development.
- Ideal for new lawns, sod, or grass plugs.
- Includes plant hormones for extra root stimulation.
- Affordable and covers multiple applications.
- Easy to mix and apply.
Cons
- Not suited for established lawns needing balanced nutrients.
- Requires dilution and careful application.
- Liquid form may not be as convenient for large lawns.
Who It’s For
This is the best choice for anyone starting a new lawn or repairing bare patches. If you’re laying sod or seeding, Fertilome’s root-focused formula will give your grass a head start.
5. Ultimate 3-18-18 NPK Lawn Food Liquid Fertilizer by Simple Lawn Solutions
Simple Lawn Solutions delivers a premium liquid fertilizer with an NPK of 3-18-18, designed for root vigor and turf hardiness. This concentrated spray is perfect for summer and fall applications, strengthening roots to handle seasonal stress and prepare for winter dormancy.
What Makes It Stand Out
This fertilizer balances high phosphorus (18%) and potassium (18%) to supercharge root growth and stress resistance. The low nitrogen (3%) keeps top growth in check, focusing energy on the roots. It includes micronutrients like iron and manganese, plus seaweed and fish emulsion for a natural boost to soil health. The 32-ounce bottle covers up to 3,200 square feet, and its hose-end sprayer makes application a breeze.
How to Use It
Attach the bottle to a hose and spray evenly across your lawn. Apply every 4-6 weeks during summer or fall for best results. Water lightly after application to help the nutrients soak in. It’s safe for all grass types, including St. Augustine, Bermuda, and fescue.
Pros
- High phosphorus and potassium for robust roots.
- Includes micronutrients and natural ingredients like seaweed.
- Easy hose-end sprayer for quick application.
- Enhances turf hardiness for seasonal stress.
- Works on all grass types.
Cons
- Smaller coverage area (3,200 sq. ft.) compared to granular options.
- Premium price point.
- May require more frequent applications for ongoing results.
Who It’s For
Homeowners looking for a premium liquid fertilizer to strengthen roots during summer or fall will love this. It’s great for lawns facing heat, drought, or heavy use.
How to Choose the Best Fertilizer for Grass Root Growth
Picking the right fertilizer depends on your lawn’s needs, grass type, and maintenance preferences. Here are key factors to consider:
Nutrient Balance (NPK)
Phosphorus (P) is the star for root growth, so look for higher middle numbers in the NPK ratio (e.g., 4-10-3 or 3-18-18). Potassium (K) helps roots handle stress, while nitrogen (N) supports green blades but should be moderate to avoid excessive top growth. For new lawns, prioritize phosphorus-heavy formulas like Fertilome or Simple Lawn Solutions. Established lawns benefit from balanced or potassium-rich options like Scotts Turf Builder.
Application Type
Granular fertilizers, like Scotts Turf Builder Lawn Food, offer slow-release nutrients and long-lasting effects but require a spreader. Liquid fertilizers, like Scotts Liquid Turf Builder or N-Ext’s bio-stimulant, absorb quickly and are easier to apply but may need more frequent use. Choose based on your time and equipment.
Lawn Stage
Newly seeded or sodded lawns need phosphorus to establish roots, making Fertilome or Simple Lawn Solutions ideal. Established lawns thrive with nitrogen and potassium for ongoing root strength, as seen in Scotts products. Stressed or recovering lawns benefit from bio-stimulants like N-Ext’s sea kelp formula.
Grass Type
All five products work on cool- and warm-season grasses, but check labels for specific restrictions. For example, Simple Lawn Solutions is explicitly safe for St. Augustine, while Scotts products are universally compatible.
Soil Health
Fertilizers with organic ingredients, like N-Ext or Simple Lawn Solutions, improve soil structure and microbial activity, enhancing root uptake. If your soil is compacted or nutrient-poor, consider a soil test to guide your choice.
Ease of Use
If you want minimal hassle, Scotts Liquid Turf Builder or Simple Lawn Solutions’ hose-end sprayers are quick and tool-free. Granular options like Scotts Turf Builder require a spreader but offer longer-lasting results.
Tips for Maximizing Root Growth
To get the most out of your fertilizer, follow these lawn care tips:
- Aerate First: Punch holes in the soil with an aerator to improve nutrient and water penetration to the roots.
- Water Wisely: Keep soil moist but not soggy after applying fertilizer. Deep, infrequent watering encourages roots to grow downward.
- Mow Properly: Cut no more than one-third of the grass height at a time to reduce stress on roots.
- Test Your Soil: A soil test reveals pH and nutrient levels, helping you choose the right fertilizer and avoid over-application.
- Time It Right: Apply fertilizers during active growth periods—spring and fall for cool-season grasses, summer for warm-season types.
- Pair with Bio-Stimulants: Products like N-Ext’s RGS enhance any fertilizer’s effectiveness by boosting soil health.
Comparing the Top 5 Fertilizers
| Product | NPK | Type | Coverage | Best For | Key Strength |
|---|---|---|---|---|---|
| Scotts Turf Builder Lawn Food | 32-0-4 | Granular | 5,000 sq. ft. | Established lawns | Versatile, nitrogen-rich |
| Scotts Liquid Turf Builder | 29-0-2 | Liquid | 6,000 sq. ft. | Quick results | Fast-acting, easy to apply |
| N-Ext RGS Bio-Stimulant | 0-0-1 | Liquid | Varies | Stressed lawns | Organic, soil-enhancing |
| Fertilome Root Stimulator | 4-10-3 | Liquid | Multiple applications | New lawns | Phosphorus-heavy |
| Simple Lawn Solutions Ultimate | 3-18-18 | Liquid | 3,200 sq. ft. | Seasonal stress | Balanced, premium formula |
Final Thoughts
Building a lawn with deep, strong roots takes the right fertilizer and a bit of know-how. For versatility and reliability, Scotts Turf Builder Lawn Food is my top pick for established lawns, delivering lush green blades and resilient roots. If speed and ease are your priorities, Scotts Liquid Turf Builder greens up fast with minimal effort. For eco-conscious gardeners, N-Ext’s RGS Bio-Stimulant boosts soil health and root vigor naturally. New lawns can’t go wrong with Fertilome Root Stimulator, thanks to its phosphorus punch. And for premium root strength in tough seasons, Simple Lawn Solutions Ultimate 3-18-18 offers a balanced, high-quality formula.
No matter which you choose, pair your fertilizer with proper lawn care—watering, mowing, and aerating—to unlock your grass’s full potential. A lawn with robust roots isn’t just prettier; it’s tougher, greener, and easier to maintain. Pick the fertilizer that fits your needs, and watch your lawn thrive.
Frequently Asked Questions
What nutrients promote grass root growth?
Phosphorus is the key nutrient for root development, encouraging strong, deep root systems. Potassium supports root vigor by improving stress resistance, while moderate nitrogen aids balanced growth. Look for fertilizers with higher phosphorus and potassium, like Fertilome (4-10-3) or Simple Lawn Solutions (3-18-18).
When should I apply fertilizer for root growth?
Apply fertilizer during your grass’s active growing season. For cool-season grasses (e.g., fescue, Kentucky bluegrass), spring and fall are best. For warm-season grasses (e.g., Bermuda, St. Augustine), summer applications work well. New lawns benefit from fertilizer right after seeding or sodding.
Can I use these fertilizers on new grass?
Yes, but choose wisely. Fertilome Root Stimulator and Simple Lawn Solutions are ideal for new grass due to their high phosphorus content. Scotts Turf Builder Lawn Food and Liquid Turf Builder are better for established lawns, while N-Ext’s bio-stimulant complements any stage.
How often should I fertilize my lawn?
Most fertilizers need reapplication every 4-8 weeks during the growing season. Granular options like Scotts Turf Builder last 6-8 weeks, while liquids like Scotts Liquid Turf Builder may need reapplying every 4-6 weeks. Always follow the product label for specific timing.
Are liquid or granular fertilizers better for root growth?
Both work well, depending on your needs. Liquid fertilizers (e.g., Scotts Liquid, Simple Lawn Solutions) absorb quickly for fast results but require more frequent applications. Granular fertilizers (e.g., Scotts Turf Builder) release nutrients slowly for longer-lasting effects but need a spreader. Choose based on convenience and lawn size.
