Starter Fertilizer for Grass Seed

Starter fertilizer differs from regular lawn fertilizer in that it’s specially formulated to boost the development of new grass seeds and seedlings. However, you need to know which starter fertilizer is best for your newly-seeded grass lawn for maximum efficacy. Also, the best time to apply starter fertilizer largely depends on when you plan to seed/overseed the lawn.

The best starter fertilizer for grass seed should have three key elements; Nitrogen, Phosphorus, and Potassium (NPK). Check for a starter fertilizer with more nitrogen and phosphorus. Nitrogen is responsible for green coloration and fast growth, while phosphorus is vital for root development critical for new grass seeds. 

Does grass seed need starter fertilizer?

Grass seed needs starter fertilizer to fast-track seedling growth in the early stages. Starter fertilizer is specially formulated to boost root development in grass seed and grass seedlings. A well-established root system is essential for grass growth.

Starter fertilizers are rich in phosphorus, the essential nutrient that facilitates root growth and development. Thus, whether you’re growing grass seed on a new lawn or overseeding in the fall/spring, using a starter fertilizer will shorten the time the grass seeds take to sprout and the new seedlings to fill in.

Note that not all phosphorus-rich fertilizers can be used as starter fertilizers. Some of these products double up as weed and feed fertilizers. The active herbicide ingredient in them can be a non-selective, pre-emergent/post-emergent compound that will kill your grass seed or young grass seedlings. 

Examples include weed and feed products containing dithiopyr, prodiamine, and pendimethalin.

If you must use a weed and feed fertilizer when planting grass seed, ensure that the active herbicide ingredient is a selective pre-emergent/post-emergent that will only target existing broadleaf weeds and broadleaf weed seeds, without harming the grass seed. A good example is a weed and feed fertilizer containing mesotrione.

Note: You can tell if a weed and feed fertilizer is not meant for new grass seed if the labeling says it controls crabgrass/crabgrass seed. Such a product will likely suppress the new grass seed too.

The 5 best starter fertilizers for seeding

The most effective starter fertilizers contain a substantial amount of phosphorus for root development of new grass and minimal, slow-release nitrogen to slow down top growth in existing grass if you’re overseeding.

The best starter fertilizers for seeding include Ferti-Lome New Lawn Starter Fertilizer, Andersons Turf Starter Fertilizer, Jonathan Green Starter Fertilizer, Scott’s Turf Builder Triple-Action Starter Fertilizer, and Yard Mastery Granular Lawn Starter Fertilizer.

1. Ferti-Lome New Lawn Starter Fertilizer

With an NPK ratio of 9-13-7, Ferti-lome New Lawn Starter Fertilizer contains more phosphorus than nitrogen and potassium. While the high phosphorus content promotes root establishment, the additional micro-nutrients help to maintain the grass seedling’s health.

The nitrogen in Ferti-lome fertilizer is urea-based, thus is only converted into a plant-usable form via gradual microbial breakdown. As such, this starter fertilizer is best used for overseeding, as the slow-release nitrogen won’t immediately give a boost to the existing grass. This minimizes the chances of the established grass crowding out the new seedlings.

Note: Ferti-Lome New Lawn Starter Fertilizer is available in various bag sizes to cater to different lawn sizes and application requirements.

2. Andersons Turf Starter Fertilizer

Andersons Turf Starter Fertilizer is a solid option for vigorous seedling development. This starter fertilizer has an NPK ratio of 18-24-12, providing enough phosphorus for root development and adequate nitrogen for top growth in new seedlings.

Andersons Turf Starter Fertilizer comes in a 50-lb bag that’s enough to cover at least 12,500 square feet of lawn. Also, it’s devoid of extra ‘micro-nutrient’ additives, making it a good option if you’re specific about the nutrients you need for your grass seed.

This starter fertilizer contains both quick-release and slow-release forms of nitrogen. It’ll boost top growth in new seedlings while also feeding established grass.

Note: While it’s best for newly-seeded turfs, Andersons Turf Starter Fertilizer can also be used to boost nutrient levels in phosphorus-deficient lawns.

3. Jonathan Green Starter Fertilizer

With an NPK ratio of 12-18-8, the Jonathan Green Starter Fertilizer is recommended for seeding and sodding. The substantial phosphorus nutrients help the new seedlings to form deep, robust, and healthy root systems. This starter fertilizer is also infused with humates to boost the efficiency of plant nutrients in the soil.

Jonathan Green Starter Fertilizer is also infused with iron micronutrients to facilitate deeper greening. This starter fertilizer remains active in the soil for up to 2 months, providing your grass seedlings with nourishment until maturity. With this fertilizer, your new grass will be better equipped to survive extreme temperatures during winter and summer.

Note: For the best results on new grass seed, Jonathan Green Starter Fertilizer is best applied in early fall, spring, or summer when temperatures are between 55-80 °F.

4. Scott’s Turf Builder Triple-Action Starter Fertilizer

Scott’s Turf Builder Triple-Action Starter Fertilizer jump-starts grass seed germination and fast-tracks root development in young seedlings. It also controls weed seeds in the soil looking to sprout.

This weed and feed product also contains mesotrione, a pre-emergent herbicide ingredient that suppresses broadleaf weeds and crabgrass seeds but doesn’t harm desirable grass seeds. With an NPK ratio of 21-22-4, this fertilizer product also contains enough nitrogen to sustain the growing grass seedlings to maturity.

5. Yard Mastery Granular Lawn Starter Fertilizer

With an NPK ratio of 12-12-12, the Yard Mastery Granular Lawn Starter Fertilizer is more than just a starter fertilizer. The ample potassium content ensures that the new grass seedlings can resist drought and diseases post-establishment.

Meanwhile, 12% nitrogen content ensures that you have a visually appealing lush green lawn. This fertilizer product also offers excellent value for money in terms of coverage, with a single 45lbs bag covering up to 15,000 square feet of lawn area.

Can you put down grass seed and starter fertilizer at the same time?

Application of starter fertilizer at the same time you’re sowing grass seed is not recommended due to the high risk of the seeds suffering fertilizer burn from excess fertilizer salts.

Ideally, you should apply starter fertilizer before sowing the new grass seed. It prevents fertilizer burn and ensures even distribution of fertilizer vis-a-vis the grass seed that’s to be planted.

Should I apply starter fertilizer when overseeding?

If you’re overseeding your existing, mature grass lawn, you should apply a starter fertilizer to enhance the survival chances of the new seedlings into adulthood. You can either apply the fertilizer before or after overseeding the turf.

It’s advisable to apply starter fertilizer a few days before overseeding with a new grass seed. Alternatively, you can choose to apply starter fertilizer within three days post-overseeding. The bottom line is the earlier you feed the soil with fertilizer nutrients, the sooner your new grass seed and seedlings can benefit.

When to apply starter fertilizer

For a lawn being established from scratch, it’s best to apply starter fertilizer before sowing the grass seed. Meanwhile, consider applying starter fertilizer before or after planting the grass seeds when overseeding. Avoid planting grass seeds while applying fertilizer simultaneously due to the increased risk of the seeds/seedlings suffering fertilizer burn.

If you apply starter fertilizer before overseeding, ensure you plant the grass seed soon after, preferably within the next three days. That’s because most of the fertilizer will have leached through the soil if you wait too long. This results in fertilizer wastage, as the existing, mature grass seed doesn’t benefit much from the starter fertilizer, which doesn’t have the correct nutrient mix for established grasses.

In terms of the season, the most appropriate time to apply starter fertilizer is in early spring or late fall when the soil is wet and cold. Such soil conditions usually result in lower rates of root growth and nutrient mobility. As such, applying starter fertilizer in such soil gives you time to monitor growth and change conditions that suit the growth requirements.

Note: Applying starter fertilizer in late spring or early fall when soil conditions are better isn’t necessary unless the soil is nutrient-deficient.

What is the difference between starter fertilizer and regular fertilizer?

Starter fertilizer typically has a higher phosphorus concentration than regular fertilizer meant for mature grass. New grass needs more phosphorus to facilitate deeper root growth and development, promoting healthy and faster grass growth.

A typical starter fertilizer contains as much phosphorus content as nitrogen or more. It’s common to find starter fertilizers with NPK ratios of 21-22-24 or 18-24-12. The ‘P’ in NPK denotes the phosphorus content. By contrast, regular fertilizer for established lawns typically has an NPK ratio of 20-4-12, with the lowest phosphorus content.

Note: Potassium (K) controls factors such as disease resistance and cold hardiness, which are only required once the grass is established. It’s lower in starter fertilizer and higher in regular fertilizer for established grass lawns.


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