how much molasses for weed

Molasses for Weed – More Than Meets The Eye

Throughout history, cannabis has been cultivated since nearly 500 BC, with cultivators adapting techniques or methods over time to grow more successfully. In the modern world of weed, there are a plethora of products to peruse for nutrients or feed for your plants. But what about kicking it back old school? Molasses for marijuana has a long-standing history among growers as a sufficient supplement for soil, bud weight and the overall health of the plant. So, is molasses good for pot plants and if so, when should you add molasses to your plants? Let’s answer those questions and more with our in-depth guide to molasses for weed.

Molasses for Marijuana: The Basics

Molasses is a thick syrupy liquid that’s a by-product of refining sugar. To refine sugar, sugarcane or sugar beet juice is boiled repeatedly. The sugar is then stripped from the mixture and what’s left is a viscous substance known as molasses. The number of times this process is repeated will determine the grade or quality of a molasses product. It also determines the exact nutrient and mineral content, so it’s important in terms of using molasses for marijuana.

When feeding marijuana plants molasses, using an organic product that’s chemical, preservative and additive-free is ideal. Therefore, we’ll next cover the types of molasses you’ll need to know more about – blackstrap molasses and unsulfured vs. sulfured molasses.

Choose Wisely: The Types of Molasses

There are two distinct differences in molasses types that you’ll want to be aware of when using it for weed, as one type can be highly beneficial for your crops while the other can be quite a detriment.

These two types of molasses are sulfured and unsulfured. The titles are often found to be confusing since both actually do contain sulfur, a nutrient that cannabis plants require. The difference is that sulfured molasses contains sulfur dioxide. Sulphur dioxide acts as a preservative and antimicrobial agent, meaning it will kill beneficial microorganisms in the soil if applied. Unsulfured molasses, however, contains only sulfur, meaning an organic unsulfured molasses will feed your plants without killing the microbes that help promote growth.

When choosing a type of molasses, you’ll also have to consider varying grades of quality. You can typically tell the grade integrity by looking at the color of the molasses itself. Lighter colored molasses is normally pure sugar syrup, while darker colored molasses, like blackstrap molasses, has been additionally refined and is chock-full of beneficial nutrients. Blackstrap molasses is the most common among growing circles, as it offers the highest levels of vitamin B, calcium, magnesium, iron and potassium.

High Yielding Strains

Plant Health Matters: How Molasses Can Help

Much of the health of your crop depends on soil composition, as this is the direct foundation for growing plants. The soil is where the benefits of molasses for plants therefore makes its biggest impression.

Cannabis plants thrive on having healthy and beneficial microorganisms present in the soil. When adding molasses to soil, you’re essentially feeding these helpful microbes and helping them to thrive too. Consequently, your soil will improve in overall structure and water retention while being enriched with additional nutrients from the molasses.

The improved health also helps to build strength against harmful conditions or other factors. For example, feeding marijuana plants molasses helps protect against pathogens and salt build-up in the soil. If you weren’t aware, salt build-up in the soil causes nutrient intake issues – a problem you can avoid thanks to molasses.

High THC Strains

Perfect Timing: When Should I Add Molasses To My Plants?

As with many growing techniques, there’s frequent disagreement among growers on when and how to add molasses to cannabis plants – during their vegetative state or during flowering. The common consensus is you can use molasses on plants throughout their entire life cycle. However, the amount should be increased during the flowering stage, and is found to be more beneficial then as well.

Although the risk of overfeeding with molasses is lower than other nutrients, be sure to monitor your molasses use at all stages of plant growth and to check for signs of stress or burn. It’s also recommended to halt use completely for flushing 2 weeks prior to harvesting. A final benefit of using molasses for weed is that it’s a natural insecticide and deterrent of pests common to cannabis such as aphids, lace bugs and white flies.

Easy-To-Grow Cannabis Strains

Using Molasses Effectively & Easily

This brings us to the most important question – how exactly do you go about adding molasses to soil? Luckily, there are a number of ways you can incorporate molasses into your nutrient regimen or routine. Let’s go over the easiest and most effective of these methods now.

Using Liquid Molasses

If you’re using a molasses product made specifically for cannabis, follow the specific instructions on the container. If not, use 2 tablespoons of molasses per 1 gallon (3.7 l) of water as a guide. Keep in mind that you can increase this as your plants grow. As a tip, keep your water semi-warm so the molasses dissolves easier.

Using Dry Molasses

Dry molasses is organic grain bits that have been soaked in molasses, which adds a level of convenience to a molasses regimen by avoiding the normally syrupy liquid. If using dry molasses, you can follow the recommendation of using 500g (17.6 oz) to approximately 4.5-6m 2 (5.3-7.18yd 2 ) of soil.

Using Molasses As A Nutrient

Another method is to use molasses when you feed with other nutrients. When doing this, make sure you monitor your soil’s pH levels, as it can cause them to change. You can also add 4 tablespoons of molasses per 1 gallon (3.7 l) of water and add it to your soil prior to planting or transplanting.

Using Molasses As A Pesticide

Many growers have found that molasses is an effective natural pesticide, as it’s been shown to help decrease populations of detrimental pests like aphids, lace bugs and white flies. To make a foliar spray, mix quarter of a teaspoon of molasses into 0.25 gallon (1 l) of semi-warm water for easy dissolving. After stirring, you can use a garden sprayer to generously apply the solution to your plants.

Using Molasses Through Compost Tea

Compost Tea is widely used to feed cannabis plants because of its high concentration of microorganisms, enzymes and nutrients. It just so happens that molasses is a key ingredient in the special feed – so rest assured, if you’re using compost tea, you’re already implementing the benefits of molasses.

Molasses On The Market

Many organically-labeled nutrient products found on the shelves today have molasses as an ingredient. You may even find that the most premium nutrient products are strictly just molasses themselves. These products are typically infused with multiple nutrients that supplement growth as much as possible. However, due to the concoction of multiple ingredients, they can end up being quite pricey. If you’re looking to save on cost while still organically protecting and supplementing your plants, pure molasses may be your best bet. Even better, organic options like blackstrap molasses are also readily available at many retail stores, including grocers.

Molasses: A Natural Syrupy Supplement

With the information you’ve acquired, you now know that molasses is more than just a syrupy food-grade liquid. The benefits of molasses for plants are overwhelming, while still remaining a natural and organic supplement option. It’s the reason why many store-bought nutrients contain the ingredient, as feeding marijuana plants molasses can be highly beneficial overall. Ensure that you follow our guidelines for choosing the right type of molasses and properly applying it to your crops for optimal growth and plant health.

Is molasses good for cannabis plants and if so, when should you add molasses to your plants? Find it out with our in-depth guide to molasses for weed

Molasses: An Excellent Supplement For Cannabis Plants

If you want to grow cannabis the natural way, there is nothing better than molasses. Learn why molasses is excellent for growing cannabis. Find out about the many advantages of molasses for strong and healthy plants.

Molasses is often overlooked among the many nutrients and additives available to cannabis growers, yet it is one of the best supplements. Molasses isn’t just rich in valuable nutrients, but it also has the ability to improve the soil, the very foundation of your grow. In addition to that, it provides many other benefits for healthy plant growth. It helps prevent common problems when growing cannabis, for example by minimising the risk for salt build up. It even doubles as an insect repellent. Let’s have a detailed look at molasses and its benefits for cannabis cultivation.


Molasses or black treacle, as it is called in the UK, is a highly viscous, dark substance that is made during refining of sugar. It is made by boiling down sugar cane or sugar beet juice into a thick syrup. Once sugar crystals are extracted, a syrup that remains is called molasses. Different types of molasses are available, they vary in sweetness and in the way they are extracted. Molasses made from sugar cane is often made into sweeteners or used as a flavouring for foods. Sugar beet molasses, on the other hand, has an unpleasant smell and is unpalatable, so it is normally used as an animal feed additive. Not all types of molasses are suitable for growing. Some molasses of low quality can contain undesired additives, such as preservatives and chemicals that you definitely don’t want in your garden. Make sure you look for organic molasses that is suitable for gardening.


Although any type of molasses will normally contain some sulphur, some molasses made from sugar cane can have sulphur dioxide added, which is why it’s called sulphured. The sulphur dioxide acts as a preservative and an anti-microbial agent to keep the raw cane fresh until it is processed. Sulphur dioxide, however, has a side-effect that makes it unsuitable for our purpose, it also kills the beneficial microorganisms in the soil. So if you’re getting molasses for growing cannabis, make sure that it is both organic and unsulphured.

There are also different types, or “grades”, of molasses, from lighter coloured molasses that is pure sugarcane syrup, to darker molasses and then blackstrap molasses which is denser and thicker than the other types. Blackstrap molasses has undergone multiple boiling and extraction processes, so that it has the highest concentration of vitamins, micro and macro elements. It is very rich in calcium, iron, magnesium, potassium and other valuable elements.


The soil that you are using to grow your cannabis is arguably one of the most important factors for strong and healthy growth of your plants. Good soil contains nutrients such as nitrogen and phosphorus, along with minerals such as potassium, iron and calcium, as well as many other compounds and nutrients. Each of these compounds is essential for healthy growth of your cannabis plants.

But the nutritional compounds in your soil, the chemicals, minerals and other inorganic substances are not all there is to make a good environment for your plants. Soil also contains beneficial microorganisms which live in it. These microorganisms are also playing a vital role in healthy growth of your plants.

Molasses is the perfect food for these microorganisms, as it gives them the ideal environment to thrive. When you supplement soil with molasses, what you’re doing is, therefore, not so much feeding your plants, but feeding the soil and the microorganisms in it. Along with providing the microorganisms with the carbohydrates and sugars that they love to feed on, molasses also has other benefits for the soil.


  • Feeds the beneficial microorganisms in the soil
  • Improves structure and water retention of the soil
  • Enriches the soil with various essential minerals and vitamins
  • Helps to prevent the build-up of pathogens that could harm your plants
  • Helps minimise the risk for salt build-up in the soil, which could cause nutrient problems
  • Acts as a natural insecticide against common cannabis pests


What makes molasses invaluable for growing cannabis isn’t just its benefits for healthy plant growth, but also the versatility in usage. You can use it like a regular nutrient that you add to your feeding schedule, you can make composts and compost teas, use it to prepare a particularly rich soil, or apply it as a foliar spray.

How much molasses you should use, normally depends on the particular strain that you’re growing and its nutrient requirements. The right dosage can also depend on your plant’s age and may be different depending on environmental factors, such as temperatures and light intensity.

When you’re starting out feeding molasses, it is recommended that you start with lower dosages at first. A good starting point can be 4–5ml of molasses per litre of water. Later, when your plants are flowering, you can increase the dosage a bit, since your cannabis plant will need more potassium. Although you can use molasses during all stages of growth, including the vegetative phase, you will likely notice the most benefits during flowering.

The risk for overfeeding with molasses is considerably lower than with mineral nutrients, but it is smart to observe your plants for any signs of stress or nutrient burn, in particular if you add molasses to an existing feeding regimen. If things look good, you can gradually increase your dosage if needed. You can add it to organic liquid fertilizers, such as compost teas. If you’re adding molasses to your existing feeding regimen, you should also keep an eye on your soil’s pH level, since any additional substance can affect it. Make sure you check your runoff pH frequently.

If you’re growing outdoors, you should know that molasses can attract wildlife, which is something you want to keep in mind.


You can use liquid molasses as we described above, but you can also use dry molasses to enrich your soil before you start growing. Despite the name, dry molasses is actually not dried molasses, it’s made with organic bits (usually grain) that have been drenched with molasses. Dry molasses makes an excellent supplement that you can mix into your soil. You need about 500g of dry molasses to enrich about 4.5–6m² of soil.


Although there are no scientific studies about using molasses as an insecticide, it has been shown effective against sucking insects, such as aphids, white flies and lace bugs, which are among the most common cannabis pests.

You can make an effective insecticidal foliar spray by mixing approximately 1.3ml of molasses (quarter of a teaspoon) into one litre of lukewarm water. Stir well, so that the molasses dissolves. Use a garden sprayer, and liberally sprinkle your plants with the mix.


A common problem with growing cannabis can be when salt from feeding mineral, non-organic nutrients builds up in the soil over time. The accumulated salt can at some point throw off the pH level in the soil, preventing the plants from taking in nutrients any longer—the dreaded nutrient lockout. Molasses works more indirectly, as compared to mineral nutrients where you simply add nutrients every time you feed your plants. This is why using molasses doesn’t come with the same risk of salt build-up.


If you buy commercial cannabis supplements and nutrients, in particular those which are labelled organic, you will find that most of them do, in fact, contain molasses. Some “special” growth supplements may indeed be nothing more than molasses, just packed in a nice bottle.

This is not to say that these supplements wouldn’t get the job done. The advantage here is simply that molasses will cost a lot less than some fancy-brand cannabis supplements, yet will provide your plants with the same benefits. What’s more, it’s easy to buy molasses: you can get organic blackstrap molasses at most grocers and in many general stores. Also, some gardening stores stock molasses.


If you want to grow good cannabis organically, you don’t need a host of expensive nutrients and supplements. All you need is some good quality soil and molasses. Turn your soil into a rich environment with the help of molasses and your plants will thrive and reward you with aromatic buds at harvest time!

Learn about the benefits of using molasses for growing cannabis the natural way.