Can You Use Too Much Seasol?

Written By:
Scott Carroll
Published On:
November 15, 2023

Seasol isn’t your typical garden fertiliser; it’s a plant tonic and soil conditioner derived primarily from seaweed. Its primary role is to improve the overall health and resilience of plants. From revitalising stressed garden beds to enhancing root development and flowering, Seasol has become a staple in Australian gardens. But as with any gardening product, the question often arises: can you use too much of it?

In our journey through gardens, both vast and compact, we’ve learned that understanding a product is key to using it effectively. So, let’s dive into the nature of Seasol, discuss its common uses in gardening, and unravel whether there’s such a thing as ‘too much Seasol’.

Science behind Seasol

Seasol is primarily made from seaweed – specifically, knotted kelp harvested from Australia and Tasmania’s clean, nutrient-rich waters. This is where the magic begins. 

Unlike synthetic fertilisers that mainly supply nutrients, Seasol works differently. Let’s see how:

  • Seasol composition: It is a unique blend of knotted kelp, natural hormones, trace elements, minerals, and amino acids, creating a wellness cocktail that offers more than traditional fertilisers.
  • Difference from fertilisers: Unlike standard fertilisers that primarily provide essential nutrients (nitrogen, phosphorus, potassium), Seasol enhances the plant’s environment and overall health, complementing fertilisers rather than replacing them.
  • Promoting root growth and plant health: Seasol is particularly effective in encouraging stronger and deeper root growth, which leads to better water and nutrient absorption, increased resilience to environmental stresses, and improved overall plant health.

Moreover, Seasol has been shown to boost the plant’s immune system. Plants treated with Seasol often have a better chance of returning from environmental stresses like heat, drought, and frost. It also helps improve the plant’s cellular structure, leading to better foliage growth, more vibrant flowers, and, for our edible gardeners, tastier fruits and vegetables.

It is important to note that Seasol is not a fertiliser. It’s crucial to understand that Seasol is a plant tonic and soil conditioner, not a direct substitute for fertilisers. Its role is enhancing plant resilience and health rather than supplying primary nutrients.

So, can you use too much Seasol?

While Seasol is generally safe and beneficial, there’s a lingering question about overusing it. Excessive use, although not as damaging as over-fertilising, may still lead to an imbalance in the garden ecosystem. 

Referring to a discussion on the Whirlpool forum, a gardener inadvertently used a much higher concentration of Seasol than recommended, raising concerns about its effects on plants. Fortunately, Seasol’s natural composition minimises the risk of severe harm but underscores the importance of following recommended usage guidelines.

Practical application and best practices

At Yard Work, we believe in putting theory into practice. Let’s explore the practical uses of Seasol based on expert advice and our own experiences.

Here are some guidelines and best practices to ensure you’re using Seasol effectively in your garden:

Proper usage guidelines

  • Dilution Rates: The recommended dilution rate for Seasol is crucial for optimal effectiveness. Generally, one capful of Seasol is mixed with a 9-litre watering can. This concentration is suitable for treating an area of about 4 square metres.
  • Application Frequency: Regular application is key. Applying Seasol every two to four weeks during the growing season is beneficial for most plants. However, during periods of stress (like extreme temperatures or transplanting), you might increase the frequency to help support your plants.

Best practices for different plant types

  • Vegetables and fruits: For your veggie patches and fruit trees, use Seasol during key growth phases – such as flowering and fruit set – to promote healthy development and yield.
  • Flowers and ornamentals: Apply Seasol during the blooming season to enhance flower production and vibrancy.
  • Lawns: Seasol promotes a lush, green lawn. For best results, apply it during the active growing season.
  • Indoor plants: Indoor plants can benefit from a milder solution of Seasol. It helps in boosting their growth and resilience to indoor conditions.

Adapting to Soil Conditions

  • Clay soils: In clay soils, where drainage can be an issue, Seasol helps improve soil structure, allowing roots to breathe and access nutrients more efficiently.
  • Sandy soils: Sandy soils often struggle to retain nutrients. Seasol aids nutrient uptake and retention, ensuring plants get what they need.
  • Potting mixes: For plants in containers, adding Seasol to your regular watering routine can boost plant health, as potting mixes often lack the diversity of nutrients found in natural soil.

Remember, the magic of Seasol isn’t just in what it does but in how you use it. Following these guidelines and adapting to your garden’s needs will set the stage for a thriving, vibrant garden.

Dealing with overdosing and plant stress:

If you think you have overused Seasol in your garden, don’t fret. While Seasol is generally safe and difficult to overapply, managing any potential overdosing is essential to responsible gardening. 

Let’s explore some strategies to tackle this situation, ensuring your plants stay healthy and stress-free:

Managing Seasol overuse

  • Dilution through watering: If you suspect a Seasol overdose, the first step is to dilute its concentration in the soil. Water the affected area thoroughly. This helps spread and reduce the concentration of Seasol around the plant roots.
  • Checking soil moisture: Ensure that the soil is not waterlogged. While diluting is necessary, overwatering can lead to other issues, like root rot. Feel the soil a few inches below the surface – it should be moist but not soggy.

Addressing plant stress post-overdosing

  • Monitoring plant response: After addressing the immediate issue, watch your plants closely for signs of recovery or continued stress. These signs will guide your next steps.
  • Soil aeration: If the soil feels compacted, gently aerate it around the plant base. This improves air circulation to the roots, aiding in recovery.
  • Balancing with fertilisers: If plants show signs of nutrient deficiency post-overdosing, consider applying a balanced fertiliser to replenish essential nutrients.
  • Using mulch: Applying a layer of organic mulch can help regulate soil temperature and moisture, providing a stable environment for stressed plants.

Preventive measures

  • Accurate measurement: Always measure Seasol accurately according to the instructions. This prevents the risk of overdosing.
  • Observe your plants regularly for signs of stress or over-fertilisation, such as yellowing leaves or stunted growth.

Remember, while Seasol is a beneficial addition to your gardening practices, understanding how to use it correctly and respond to missteps is key to a healthy garden.

Alternative products and comparative analysis

In the gardening world, Seasol is just one of many products we can choose to enrich our gardens. Let’s compare Seasol with other popular products like Charlie Carp and traditional fertilisers, delving into their pros and cons. 

For more detailed comparisons, check out our in-depth PowerFeed vs. Seasol and Charlie Carp vs. Seasol analyses.

Seasol vs Charlie Carp

Charlie Carp vs Seasol


  • Pros: Enhances root growth, improves plant resilience, and aids in overall plant health.
  • Cons: Does not supply major nutrients directly to plants; best used as a complement to fertilisers.

Charlie Carp

  • Pros: Provides a good source of nutrients, especially nitrogen, and is environmentally friendly, utilising invasive fish species.
  • Cons: May not offer the same level of root development and stress tolerance as Seasol.

Seasol vs traditional fertilisers


  • Pros: Acts as a tonic, improving the soil environment and plant vitality; beneficial for root development and stress resistance.
  • Cons: Not a direct source of key nutrients like N, P, K; requires pairing with fertilisers for complete nutrition.

Traditional fertilisers

  • Pros: Directly provide essential nutrients required for plant growth; immediate impact on plant health.
  • Cons: Lacks the holistic benefits of soil conditioning and plant resilience in products like Seasol.

Choosing between Seasol, Charlie Carp, and traditional fertilisers depends on your garden’s needs. Seasol is a great choice for overall plant health and resilience. Traditional fertilisers or nutrient-rich options like Charlie Carp might be more suitable for direct nutritional needs.

Remember, the best approach often combines these products to achieve a well-rounded and healthy garden.

Final thoughts 

Seasol stands out for its unique ability to condition the soil and bolster plant health, particularly root development and resilience. However, it’s important to recognise that it’s part of a broader gardening strategy, complementing rather than replacing traditional fertilisers. Products like Charlie Carp or standard fertilisers offer more targeted solutions for those seeking direct nutritional supplements.

The key takeaway for us gardeners is to understand the specific needs of our plants and soil. Whether using Seasol for its holistic benefits or opting for nutrient-rich fertilisers, the goal is to create a harmonious environment where our plants can thrive.

So, as we put down our gardening tools for the day, let’s reflect on the wealth of options available to us. Each garden is unique, and with the right knowledge and tools, we can turn any patch of earth into a thriving oasis of life and colour.

As always, happy gardening!