Weed Grow Guide by Royal Queen Seeds

By Luke Sumpter Reviewed by: Silvia Maroto

Molasses serves as an important tool in the arsenal of many organic cannabis growers. This sweet and sticky substance introduces plenty of sugars and beneficial nutrients into the growing medium, feeding both the plants themselves and beneficial soil microbes.

What Is Molasses?

A dark, sweet, and syrupy substance, molasses stems from the processing of sugars from sources including beets and sugarcane[1]. Molasses is the residue left from the crystallization process of sugar, from which no more sugar can be obtained by physical methods. It is made by boiling, for example, the juice of the sugar cane, until the partial evaporation of the water, forming a syrupy product semi-crystallized[2].

  • Why Is Sugar Important for Cannabis?

It might come as a bit of a surprise, but sugar is vital to healthy and robust cannabis plant development[3]. Not only is sugar responsible for energy metabolism, but it also serves as a type of chemical messenger that helps promote health throughout the cannabis life cycle[4]. The production and distribution of sugars is something cannabis does naturally, but it can use assistance in the form of various practices and supplements. Enter molasses.

What Are the Benefits of Molasses for Cannabis Plants?

While sometimes used as a sweetener or cooking ingredient, molasses is also used to improve the health and yield of cannabis plants. This sticky syrup contains a wealth of nutrients that help to drive plant development and soil health, including:

  • Carbohydrates: These simple sugars serve as a life-giving energy source to beneficial microbes in the soil. As you feed bacteria and fungi in the rhizosphere, they multiply and help plants tap into nutrients.
  • Calcium: This mineral plays a crucial role in plant physiology, contributing to tissue growth and the structural integrity of cell walls.
  • Iron: This essential plant micronutrient plays a fundamental role in metabolic processes such as DNA synthesis, respiration, and photosynthesis.
  • Selenium: Selenium helps to reduce plant stress and activates important antioxidants and enzymes.
  • Copper: Copper helps plants to create energy and respire, and also plays a role in the breakdown of carbohydrates and proteins.
  • Magnesium: Magnesium forms the core of the chlorophyll molecule in plant tissue, meaning deficiencies can lead to a lack of chlorophyll and stunted growth.
What Are the Benefits of Molasses for Cannabis Plants?

Types of Molasses

Now you know the many benefits that molasses can offer the cannabis grower, from key plant nutrients to sugars that feed microbial life[5]. When shopping for molasses, you’ll quickly discover a few different types. Check out the differences below to see which is ideal for weed.

  • Light Molasses

Light molasses, also known as “first” or “sweet” molasses, is less rich and lighter in color than other options. It is made from the first boiling of either beet juice or sugar cane. Light molasses is, as you might guess, light in color and offers a milder, or sweeter, flavor that is more palatable because only a small percentage of the sugar has been extracted. You’ll find light molasses mainly in baked goods, marinades, and sauces.

  • Medium or Dark Molasses

Dark or “second” molasses is deeper in color and made following the second boil of sugar cane or beet juice. These types feature a much stronger flavor than light molasses, and the dark color stems from the increased concentration of carbohydrates. Dark molasses is less sweet and provides the underlying flavor of gingerbread cookies.

  • Blackstrap Molasses

Blackstrap molasses takes richness and darkness to another level. It results from a third boil, and as such is far less sweet and much more bitter than others. Blackstrap molasses is extremely viscous, dense, and often appears in savoury recipes such as baked beans.

  • Treacle

Treacle differs from molasses in that it features less sucrose and appears much lighter. Although sweeter than all types of molasses, it also possesses a slightly bitter edge. However, much like molasses, treacle also comes from the boiling of raw juice. Manufacturers simply remove the syrup from the boil earlier in the process.

  • Sulphured vs Unsulphured Molasses

Sometimes, manufacturers add sulphur dioxide to their molasses. This acts as a preservative and enhances the shelf-life of the product. However, this process can impact the flavor of molasses and also make it unsuitable for use in the garden.

As far as taste goes, the addition of sulphur dioxide leaves molasses with a chemical flavor. The preservative also acts to kill microbes, which means it will damage beneficial communities within your soil. For this reason, always choose unsulphured molasses for use in the garden.

Molasses or Honey?

If molasses contains sugars that help microbes thrive and plants grow, why not use honey instead? Honey contains plenty of sugar, and even works as a rooting stimulant when cloning cuttings. However, molasses brings more than just sugar to the table. Large quantities of essential nutrients make molasses the superior choice when aiming for massive yields.

How and When To Use Molasses in Cannabis Growing

So, with the above knowledge in mind, how should you go about using molasses when it comes to growing weed? Check out the techniques below to discover different ways to use molasses in your garden or grow room.

Which Type of Molasses Is the Best for Cannabis?

Before we delve into how to use it, let’s settle on the best type of molasses to use. We recommend aiming for unsulphured blackstrap molasses. This thick and dark version offers a much more concentrated source of sugars that will kick the microbial life in your soil into overdrive.

Using Molasses in Soil

You can enhance your soil with molasses quickly and easily. There are two ways to add it to your growing medium, either through water or in its dry form.

Watering With Molasses

Use these steps to water your plants with molasses:

  1. Fill up a watering can with lukewarm water.
  2. Add 4–5ml of molasses per litre of water and stir thoroughly.
  3. Maintain this concentration throughout the vegetative phase and apply 1–2 times per week.
  4. Keep a close eye out for any signs of nutrient burn, and dial back your feeding if you see these occur.
  5. Increase the dose to 8–10ml during the flowering stage to meet increased demand for potassium.
Using Molasses in Soil

Improve the Soil With Dry Molasses

Dry molasses is a mix of grains drenched with molasses. Here’s how to use it.

  1. Use a scoop to measure out 17.6 oz of molasses.
  2. Apply this volume for every 4–6m² of soil to enrich your growing medium at the start of the growing cycle.
  3. Apply the same quantity just below the topsoil at the start of the flowering phase.
Using Molasses in Soil

Using Molasses as a Foliar Spray

Foliar sprays allow nutrients to pass directly through the leaves via the epidermis and tiny stomata (pores). This allows growers to rapidly address any signs of deficiency.

To make your own molasses foliar spray, use these steps:

  1. Add one litre of lukewarm water into a spray bottle.
  2. Add a quarter of a teaspoon of molasses into the bottle.
  3. Mix the solution thoroughly by stirring and shaking.
  4. Spray liberally onto the leaves of your cannabis plants.
  5. Reapply once every two weeks throughout the growing cycle.

Using Molasses as a Natural Insecticide

You can also use the above formula to deal with pest insects[6]. Not only will this preparation deliver key nutrients directly through the leaves, but it will also help to prevent and dislodge sucking insects that do damage to leaves, stems, and branches.

This formula works well at dealing with pest insects such as aphids, whiteflies, and lace bugs.

Using Molasses in Soil

Using Molasses in Compost Tea

Compost tea harnesses the power of microbial life and crucial nutrients[7]These formulas blast plants with life-giving substances that help to boost plant health and increase your productivity.

Add one teaspoon of unsulphured blackstrap molasses to your compost tea preparation to bestow more carbohydrates and yield-enhancing minerals.

Tips for Using Molasses With Cannabis

Using the recipes and methods above will help to increase the health of your plants and soil while improving yields along the way. The tips presented below will help you refine the skill of working with molasses when growing cannabis. Learn when to stop using it, how to combine it with other amendments, and what the best alternatives are.

  • When To Stop Using Molasses

Using molasses can become problematic under some circumstances[8]. For example, it’s possible to give your plants too much of a good thing. When you add too many nutrients to the soil, the roots and leaves can become burnt. If you spot signs of nutrient burn, stop applying molasses until the problem resolves.

  • Combining Molasses With Rhizobacteria

Molasses helps to feed the microbes that already exist in the soil. But you can add an extra punch to your preparation by adding rhizobacteria as well[9]. This type of bacteria does a world of good by helping to free up nutrients and combating pathogens.

  • Molasses vs Commercial Supplements

Take a look at the ingredients list on a lot of organic supplements. Notice anything consistent? Loads of them contain molasses! Molasses achieves very similar results to a lot of pre-made solutions available on the shelves. However, some of these products contain additional goodies, and some growers simply prefer to use these supplements instead of taking the time to make their own.

  • Molasses Alternatives

Molasses is easily one of the cheapest and most effective soil enhancers out there. However, if you can’t access molasses, there are a few alternatives that also work well. These include:

  • Honey
  • Agave
  • Corn syrup

Why Molasses Is Excellent for Healthy Cannabis Plant Growth

Molasses contains a huge array of crucial minerals needed for weed plants to survive and thrive. Alongside this massive benefit, it helps to bring the soil to life by feeding beneficial bacteria and fungi. This then enables plants to tap into even more nutrients already present in the soil. The best part? Molasses is inexpensive but super effective!

External Resources:
  1. The effects of fulvic acid and sugar cane molasseson yield and qualities of tomato https://irjabs.com
  2. Experimental investigation of molasses as a sole nutrient for the production of an alternative metabolite biosurfactant https://www.sciencedirect.com
  3. The Effects of Sugar Beet Molasses Applications on Root Yield and Sugar Content of Sugar Beet https://www.biotechstudies.org
  4. Effect of Molasses and Organic Fertilizer in Soil fertility and Yield of Spinach in Khotang, Nepal https://www.nepjol.info
  5. Evaluation of baker's yeast strains exhibiting significant growth on Japanese beet molasses and compound analysis of the molasses types https://www.sciencedirect.com
  6. Effect of Molasses as a Spray Additive for Control of the Bollworm and Tobacco Budworm https://academic.oup.com
  7. Effect of Molasses on Regrowth of E. coli O157:H7 And Salmonella in Compost Teas https://www.tandfonline.com
  8. Efecto del uso de melaza y microorganismos eficientes sobre la tasa de descomposición de la hoja de caña (Saccharum officinarum) https://dialnet.unirioja.es
  9. Plant Associated Rhizobacteria for Biocontrol and Plant Growth Enhancement https://www.frontiersin.org
This content is for educational purposes only. The information provided is derived from research gathered from external sources.

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