Using Molasses for Cannabis Plants

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Molasses isn’t just for baking cookies anymore. Cannabis growers everywhere have started discovering the incredible benefits of molasses for growing better cannabis.

What is molasses?

Known as black treacle in the UK, molasses is a dark, viscous substance produced during the process of refining sugar. First, sugar beet juice or sugar cane is boiled down into a thick syrup.

Then, once the sugar crystals are extracted to make sugar, the syrup remaining is molasses.

Organic Black Cane Sugar Molasses in a Bowl

Molasses comes in several types, varying in extraction method and sweetness. Molasses extracted from sugar cane is typically made into a food flavoring or sweetener, while molasses extracted from sugar beets has a bad taste and smell and is, therefore, used primarily as an additive in animal feed.

Why is molasses so beneficial to cannabis plants?

There are two ways in which molasses benefits cannabis-plant growth.

One of the key factors for any cannabis grower who grows in soil rather than hydroponically is the quality of the soil itself. Healthy soil supportive of growing healthy cannabis plants is rich in nutrients like phosphorus and nitrogen and minerals like iron, calcium, magnesium and potassium.

As cannabis plants grow, however, and they continue to feed on these nutrients, they progressively deplete these nutrients until there are none left in the soil. It is, therefore, necessary to supplement and replenish these nutrients to continue sufficiently nourishing your cannabis plants.

Small Marijuana Bud Growing Close Up on Cannabis Pl

Molasses contains most of the same nutrients found naturally in healthy soil, making it an appropriate supplement or additive to keep cannabis plants consistently well-fed.

In addition, soil contains many microorganisms also beneficial for healthy cannabis and prolific growth. Molasses can provide an ideal food source for these microorganisms, with sugars and carbohydrates that can help them thrive.

What does molasses do for cannabis plants?

Molasses provides numerous benefits for cannabis growth, including:

  • Enriching the soil with an array of vital vitamins and minerals
  • Feeding the beneficial microorganisms living in the soil
  • Helping prevent harmful pathogen buildup
  • Helping reduce the chances of nutrient-blocking salts building up in the soil
  • Improving the soil’s structure and ability to retain water
  • Serving as a natural insecticide combatting common pests to cannabis gardens

On that last item, using molasses as an insecticide, some growers find it useful in combatting aphids, white flies and other pests.

How do I use molasses with my cannabis plants?

Using molasses effectively with cannabis plants requires careful attention not only to the type of molasses you’re using but how you use it, including how much you use at each stage of cannabis plant development.

How much molasses should I use?

The amount of molasses to use depends on several factors, including:

  • The cannabis strains you’re growing and their particular nutritional needs
  • Your plants’ age
  • Environmental factors like light, temperature and humidity levels

When first starting out using molasses with your cannabis plants, it may be best to start slowly, with a light dose initially and build up gradually, as your plants age.

A good starting dose of molasses for cannabis plants in their vegetative, or pre-flowering, stage is 4 to 5 ml per liter of water. Once the plants start flowering, you can then increase the dose slightly.

It is during the flowering stage when you can most visibly notice the effects of molasses on your cannabis plants. When starting out using molasses with your cannabis plants, observe your plants closely for any signs of strain or stress, including nutrient burn or other types of damage.

Molasses treacle in dish

Fortunately, molasses is less known to cause nutrient burn than other additives. Once you see that your plants are responding well to the molasses, without any negative indications, you can gradually increase the dose.

If you notice any negative signs, however, stop using the molasses altogether until the plants recover. Then, once they’ve resumed healthy, prolific growth or flowering, you can consider adding molasses back in at an even lighter dose.

Be aware, as well, of the effect of molasses on the pH of your water, feeding regimen and soil. Always regulate the pH of anything touching your cannabis plants to make sure they’re pH neutral, or approximately 6.8-7.2.

Can I use any molasses products or do I need something specific?

For growing cannabis, only certain types of molasses are suitable.

Organice vs. Inorganic Molasses

Low-quality molasses, for example, may contain additional additives like chemicals and preservatives that could be harmful to cannabis plants or, at least, counterproductive to the cannabis-growing process. For this reason, only organic molasses free of added chemicals and preservatives is suitable for growing cannabis.

Sulphured vs. Unsulphured Molasses

Most molasses naturally contains some amount of sulphur, but molasses from sugar cane may also contain added sulphur dioxide as a preservative and anti-microbial agent to keep fresh the raw sugar cane prior to processing.

A small plant of cannabis seedlings at the stage of vegetation

This type of molasses is called sulphured molasses. Sulphur dioxide is unsuitable, however, for growing cannabis. For this reason, unsulphured molasses is the only type suitable for growing cannabis.

Low-grade vs. High-grade Molasses

There are also various types, or grades, of molasses named for their level of viscosity, as follows:

  • Light molasses
  • Medium molasses
  • Dark molasses
  • Blackstrap molasses
  • Treacle

Of these, blackstrap molasses contains the highest concentration nutrients, including macro-elements, micro-elements, vitamins and minerals like iron, calcium, potassium and magnesium. For these reason, blackstrap molasses is the most suitable type of molasses to use for growing cannabis.

Put all these distinctions together, and you find that the most suitable form of molasses for growing cannabis is organic unsulphured blackstrap molasses.

How do I apply molasses to my plants?

One of the most extraordinary benefits of using molasses in a cannabis garden is not its nourishing qualities at all but its immense versatility for growers.

How do I apply molasses to my plants?

You can:

  • Use it like you would any other nutrient additive to the food you feed your plants
  • Apply it directly to the leaves in the form of a foliar spray
  • Make it into a compost or compost tea
  • Enrich the soil by adding it directly into the soil during the soil-preparation phase of growing

On that last item, using molasses to prepare your soil, you can use dry molasses, which, despite its name, is actually comprised of dried organic grains and other bits that have been soaked with molasses. For this procedure, consider using around 500 g dry molasses with every 4.5 to 6 square meters of soil.


Will molasses make my marijuana buds bigger? Will it make them taste sweeter?

Due to the array of beneficial nutrients molasses contains, adding it into your cannabis-growing regimen can help produce both bigger and sweeter buds.

What stage of cannabis plant growth should you use molasses?

You can use molasses during both the vegetative and flowering stages of growing cannabis, though the benefits are more visibly noticeable during the flowering stage.

Can I use molasses on my outdoor cannabis plants?

Molasses will work just as effectively on cannabis plants you grow outdoors as those you grow indoors. One thing to be aware of, however, is that is could attract wildlife pests that could damage or destroy your plants.