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  • Naomi Stephens | Permaculture Designer

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

Updated: Mar 4

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

Molasses are commonly associated with being 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 beets are refined using a centrifugal process, sugar crystals remain. When those crystals are refined, they make a light-colored form of molasses that contains more sugar 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 that can be used as a liquid fertilizer.

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

Different kinds of molasses depend on how many times the sugar crystals are refined.

When the sugar crystals from cane or beet juice are refined just once, the result is a light brown-colored 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 mainly in the food industry for things like barbeque sauces and preparing whole-grain bread, gingerbread, cookies, and pies. See image:

Beware, though, light molasses aren't as healthy as blackstrap because they contain mainly 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; I think 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 sulfured 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, they have no sulfur dioxide. So sulfur dioxide is added to them to help preserve the sugar cane or sugar beet for longer. This is why it's called sulfured molasses.

When sugar cane or beets are fully matured during 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?

Blackstrap molasses can be obtained by refining sulfered or unsulfered sugar cane or sugar beets. The results are either suffered blackstrap molasses or suffered 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 plants should use as a liquid fertilizer is 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. It 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 an excellent plant fertilizer.

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 defenses are better at dealing with pests.

For example, molasses and 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, mix two tablespoons of unsulfured blackstrap molasses 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 apply the molasses to your plants individually, 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 to a compost pile. Compost piles have many beneficial microbes and mycorrhizal fungi in breaking down your organic material to compost. Adding blackstrap molasses will help provide nutrition to these microbes so they can have more energy and benefit 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 faster 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, your soil will become too acidic.

Soils that are too acidic cause a problem for plants taking in nutrients. Plants generally like soils to have 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.

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