Fertiliser Review: Eco-Seaweed by Organic Crop Protectants – Part 1

Trial and error is the creed of the home gardener. You make a mistake – you learn from it. That’s how I have been gardening for years. There’s no shame in making a mistake when you learn from the results. To take my learning to the next level I have been trailing a new fertiliser routine for my plants in conjunction with the soil-less potting mix recipe that I have also been trailing. For this test I am pitting Eco-Seaweed, a product by Eco Organic Garden, against Seasol Seaweed Concentrate + Manutec Liquid Potash, against soluble All Purpose Miracle-Gro®.

Why change what isn’t broken?

camellia flower after seaweed solution feed

Enormous camellia flower after seaweed fertiliser applied for the first time.

For years I have been using Seasol liquid seaweed amended with liquid potash. I get really great results using that formula. There was a very old Camellia at my old house in Queensland. For 5 years it never flowered once. Sporadically watering it with seaweed immediately rewarded me with the most spectacular Camellia flower I have ever seen! The flower weighed so much that when they fell from the plant they’d hit the ground with a tremendous thud! See the picture on the right to see what I mean.

Fertiliser Selection

As I said before, I have used Seasol and added additional Potash on my plants for years with great results. However I was always a bit concerned about using seaweed as it’s difficult to get a clear picture of the NPK number (NPK is the relative weight of Nitrogen, Phosphorous & Potassium in the fertiliser). I believe liquid seaweed fertiliser contains a high amount of material thats great for beneficial microbes to break down into nitrogen, however I haven’t been clear about the phosphorous levels in the seaweed. As Hibiscus don’t tolerate high amounts of phosphorous I was always concerned. However I have seen no chlorosis that would indicate too much phosphorous has been applied. However, I have also never compared, directly, head-to-head different fertilisers at the same time. I’m excited to see the results… aren’t you?


I researched the Eco-Seaweed product and it looks promising, so I bought a batch. I am enthusiastic to see the results of this product. The Eco-Seaweed product has an NPK value of 1,1,16. Which seems to be a good amount of potassium, but a very low amount of nitrogen. A low middle number (phosphorous) is recommended. So I will be augmenting it with it’s sister product, Eco-Aminogro. The companion product contains an NPK of 2.7,0.4,0.7 which should boost the nitrogen to a desired level, in combination with the manure in the soil. The Eco-Aminogro also contains trace elements and vitamins. It also claims to include naturally occurring growth hormones derived from seaweed, which I can’t speculate as to how the hibiscus plants will respond to it. That’s why we test! If this product is successful it would remove my requirement to supplement potash into my fertiliser mix.

Seasol + Potash

My regular fertiliser routine consists of weekly feedings in the warm months with 10ml of Seasol plus 10ml of Manutec liquid potash added to 9L of water. It has served me well. But the unknown NPK of the overall mix means that I am never sure if I am applying the fertiliser at the correct dosage. This experiment will compare my regular routine against some alternatives.


I don’t use this product regularly. I do however occasionally supplement it from Seasol + Potash and give a dose of All Purpose soluble Miracle-Gro. The reason I do this is to introduce trace elements, as well as much needed magnesium to the plants. Although this product would be theoretically suitable for regular feeding. I just don’t use it. I included it into this test because I wanted to see the results of using it on a regular basis compared with the other two.

Experiment begins: Plant Selection

To start this experiment I selected 4 plants of the same variety, Hibiscus Pink Chiffon. I made sure that all 4 plants are the same age, the same size and were repotted into the same soil mix at the same time, as well as making sure that all 4 plants have the same size root-balls. They were in need of this attention anyway, all of them were root-bound in their previous pots.

All 4 were repotted from 75mm pots to 140mm pots at the same time.

They all were cut back to the same height, and all 4 were in need of attention.

You can see from the strength of the initial photos that the plants we’re too spindly and needed some care and attention. The perfect candidates to see how the new soil-less recipe can be amended with the use of 3 fertilisers. The 4th plant will be the control plant. It will receive only water and no fertiliser at all only what is available in the soil-less potting mix. Which is only cow manure.

Pink Chiffon - Plant A - Eco-Seaweed Pink Chiffon - Plant B - Seasol + Potash Pink Chiffon - Plant C - Miracle-Gro Pink Chiffon - Plant D - No Fertiliser
 Plant A  Plant B  Plant C  Plant D
Eco-Seaweed Seasol + Potash All Purpose Miracle-Gro No Fertiliser
Applied weekly at recommended application rate. Applied weekly at recommended application rate. Applied weekly at recommended application rate. Control plant receives no fertiliser.

Every 4 weeks I will be providing an update to this experiment. Keep an eye out for future updates. I will update this post and include a link to each update as it occurs.

Wish me luck!