top of page
  • Naomi Stephens | Permaculture Designer

How to Make Fertilizer with Molasses | Benefits of Molasses for Plants

Updated: Oct 20

Part of being sustainable is finding new uses for things you may already have in your home. Doing this will achieve the permaculture principle of getting a second yield.

Molasses are commonly associated as a healthier sweetener, due to their high mineral content. Not many are aware that it makes for excellent garden fertilizer.

What is molasses?

When sugar cane or sugar beet is refined using a centrifugal process, what remains are sugar crystals. When those crystals are refined once more, they make a light coloured form of molasses, that contains more sugar in it and is typically used in baking.

When those crystals are again refined for a second or third time we finally get to what's called blackstrap molasses, and that's the type of molasses for plants can be used as a liquid fertilizer.

What's the difference between light, regular and blackstrap molasses?

There are different kinds of molasses depending on how many times the sugar crystals are refined.

When the sugar crystals from cane or beet juice are refined just once, the results are a light brown coloured syrup. This is called light or regular molasses.

It tastes milder than blackstrap molasses and is much sweeter because it has a higher quantity of sugar crystals in it.

Light Molasses
Light molasses are used for food, it's not suitable for fertiliser

You'll find light molasses mostly in the food industry for things like barbeque sauces, preparing whole-grain bread, gingerbread, cookies, and pies. See image:

Beware though, light molasses aren't as healthy as blackstrap because it contains mostly sugar and less nutrition. This is why we don't use light molasses for plants.

When those crystals are again refined for a second or third time we finally get to what's called blackstrap molasses, and that's the type of molasses for plants that can be used as a liquid fertilizer.

Blackstrap molasses tastes bitter, in my opinion, it tastes like a stale coke drink. As mentioned above, you can get the blackstrap molasses by increasing the refinement process of the sugar crystals for a second and third time.

What's the difference between sulfured and unsulfured molasses?

The terms sulphured and unsulfured molasses are just another way of classifying molasses based on how mature the sugar cane or sugar beet was when the refinement process started.

When sugar cane or sugar beets aren't fully mature, there is no sulfur dioxide in them. So the sulfur dioxide is added to them in order to help preserve the sugar cane or sugar beet for longer. This is why it's called sulfured molassess.

When sugar cane or beets are fully matured at the time of processing, there's no need to add sulfur dioxide to them. This kind of molasses is called unsulfured molasses.

Can blackstrap molasses be sulfured or unsulfered?

Yes, blackstrap molasses can be obtained by refining sulfered or unsulfered sugar cane or sugar beets. The results are either unsulfered blackstrap molasses or sulfered blackstrap molasses. The label should say specifically which one you have.

What kind of molasses should be used for plants?

The kind of molasses that should be used for plants as liquid fertiliser, is the organic unsulfered blackstrap molasses.

It must be unsulfered because sulfured molasses can kill the microbes in the soil, which will slow down the growth of plants.

See below or click here for the brand of pure black strap organic molasses that I recommend on Amazon.

Can blackstrap molasses fertilizer be used with other fertilizers?

Molasses can complement organic liquid fertilizers, such as alfalfa meal tea, compost tea, kelp, and nettle tea, to boost the overall performance.

Benefits of using molasses as a fertilizer

  1. Helps build soil nutrition

  2. It feeds beneficial microbes

  3. Helps strengthen your garden against pests and infestations

  4. Blackstrap molasses is a non-toxic organic fertilizer

1. Helps build soil nutrition

Molasses in organic fertilizers means that the healthy microbes in the soil have enriched food. As a result, their growth is enhanced.

Molasses can contribute to an organic garden by becoming a great fertilizer for plants.

Molasses can help plants grow because it adds more nutrients, blackstrap molasses contains:

  • 20% vitamin B6

  • Manganese

  • Magnesium

  • Potassium

  • Iron

  • Calcium

2. It feeds microbes

Also, the sugar contents in molasses include glucose, sucrose, fructose, and a host of other micronutrients. Microbes living in the soil near plants love sugar as it's needed for energy. So, using molasses as a fertilizer will mean feeding these microbes, which will aid your plants to grow better.

There are several benefits of using molasses as a fertilizer.

3. Helps the strength of your garden against pests

Molasses increases the general strength and vigor of the plants. As a result, the plant's own defenses are better at dealing with pests.

For example, molasses together with milk, can help fight against powdery mildew. This is a white substance found particularly on house plants.

4. Molasses is a non-toxic organic fertilizer

Make sure you buy organic fertilizer as this is less likely to have any pesticide or herbicide residue that will kill any beneficial microbes in your soil.

How to use molasses as a fertilizer?

There are three main ways of using blackstrap molasses for plants.

  1. Apply molasses to plants

  2. Add molasses to a compost tea

  3. Add molasses to a compost pile

1. How to apply molasses to plants

You can spray the blackstrap molasses onto your plants. To do this, take two tablespoons of unsulfured blackstrap molasses and mix it with a gallon of water. This will ensure that the thick consistency of the molasses does not end up blocking the nozzle of the spray bottle you use.

If you are individually applying the molasses to your plants, take a clean bowl and pour in a gallon of water. Add two tablespoons of the molasses into the bowl and stir thoroughly to combine the two ingredients properly. Use the same ratio for all the plants. Pour any residual mixture onto the soil around the plant.

2. How to add molasses to a compost pile or compost mix

You can add your blackstrap molasses mixture on a compost pile. Compost piles have lots of beneficial microbes and mycorrhizal fungi in the breaking down of your organic material to compost. Adding blackstrap molasses will help provide nutrition to these microbes so that they can have more energy and serve as beneficial microbes to your plants. The ratio to add will be two tablespoons per gallon of water.

3. How to add molasses to a compost tea

Compost teas are great fertilizers for plants because they provide extra nutrition and microbes. This can be great for container gardens where replacing fertility is a routine requirement.

Add the same ratio of two tablespoons of molasses per gallon of water into your compost tea. This will feed the microbes and make them multiply at a faster rate than without a food source like molasses.

Can you give a plant too much molasses?

Molasses are highly acidic. If you use too much molasses for plants, then your soil will become too acidic.

Soils that are too acidic cause a problem for plants taking in nutrients. Plants generally like soils to be a comfortable neutral ph of around 7.

This is because most soil nutrients are only available to plants in that ph. See the graph below which shows that most nutrients are available at neutral.

I hope you found this useful, if you'd like to learn more, then subscribe at the bottom of the page for exclusive resources and updates.

Get free resources, useful, well researched new ideas. Subscribe.

Subscribe for free Permaculture resources periodically. 

Subscribe for more relevant information on small space gardening and Urban permaculture. Be the first to see exclusive and new content. Be updated on the latest on what's going on in the urban gardening world.

See More

bottom of page