How to


Molasses and Cannabis

Cultivators looking for a versatile secret weapon to elevate their crop should consider molasses. Cost-effective and organic, this supplement can be applied to cannabis plants to improve soil fertility and promote growth. Growers can ensure a healthy and fruitful cannabis crop by properly using molasses to substantially strengthen their grows without breaking the bank.

Organic growers are not only cultivating plants, they are also managing a host of beneficial soil bacteria and microorganisms living in close concert with their upstairs neighbours. These microorganisms (also known as microbes) promote plant growth and soil health in a variety of ways, such as processing nutrient compounds into a format usable by plants and improving water retention. The microbes need to eat just like the plants and growers do, and regularly applying molasses to the soil can ensure they keep firing on all cylinders and continue to make life easier for cannabis plants.

Read on to find out more about this multifaceted organic product and how cannabis plants and soil can enjoy the many benefits of molasses.

More Than a Food Sweetener

Molasses is a byproduct of the process of sugar production. Sugar cane or sugar beet juice is boiled down into a thick syrup, and sugar crystals are extracted, leaving the syrup, or molasses product, behind. Growers may be familiar with molasses as a syrup that can be used in cooking as a food sweetener, but it contains plenty of carbohydrates needed to feed microorganisms in the soil as well as usable nutrients for the plants.

Cannabis growers looking for molasses to supplement their plants should make sure to use organic molasses appropriate for gardening. The quality of molasses can vary, with lower quality grades containing preservatives and additives that would be detrimental to plant health. One prominent antimicrobial preservative to keep an eye out for is sulphur dioxide which will kill the microorganisms the grower is trying to feed.

Molasses is sold either as sulphured or unsulphured. While both varieties will contain sulphur – an essential nutrient that is needed for chlorophyll production – “sulphured” actually refers to the presence of beneficial microbe-eradicating sulphur dioxide. Growers should buy organic unsulphured molasses and feed their microorganisms correctly to increase their population and activity.

There are also different types of molasses depending on the number of times it has been refined. Light coloured molasses is generally produced after the first extraction when the syrup mixture is boiled down once to extract raw sugar. Any subsequent extractions will darken the mixture and further concentrate sugars and minerals.

“Blackstrap” molasses is denser and thicker than other types, having been refined the most times. As such, it also contains essential nutrients in the highest concentrations. Growers should look at medium-dark or blackstrap molasses for treating their soil with higher amounts of iron, magnesium, and calcium. These micronutrients can be quickly depleted during plant growth and replenished safely using liquid molasses.

Molasses also contains potassium (K) which helps promote plant vigour and productive growth. Potassium eases the transport of water, nutrients, and carbohydrates within plants. Cannabis plants with good levels of potassium express thick, strong stalks and stems, significantly developed root growth, and full, heavy flowers.

Beneficial root microorganisms such as mycorrhizae feed off of sugar released by plants at the root tips. This diet can be supplemented by molasses, and the grower should expect more active mycorrhizal activity (expressed as fine, white hairs on plant roots) after feeding with molasses. Mycorrhizal webs living on plant roots allow for the absorption of nutrients the roots would not otherwise reach, increasing nutrient uptake and thus plant growth.

Cost-effective and Versatile

In addition to being a relatively cheap, organic method of feeding beneficial microbes and a source of nutrients and vitamins, molasses can act as a soil conditioner. By improving the structure and water retention of soil, molasses helps it stay moist. This will reduce the need for watering and prevent nutrients from leaching away, stabilising plants against many nutrient deficiencies that would stunt growth or weaken their immune responses against diseases.

Growers worried about nutrient lock-out caused by the salt buildup from feeding plants non-organic mineral nutrients can bypass that risk entirely with the use of molasses. Molasses is safe to use with other nutrient feeds as a substitute for certain compounds but may affect the ph of the soil. It can also be used together with compost teas, kelp, and other organic fertiliser mixes (be sure to ph any solutions between 5.8 and 6.2 before application).

Regularly feeding beneficial soil microbes molasses will cause their populations to rise, which can, in turn, deter pests that spend part of their life cycle in the soil, such as fungus gnats and thrips. When used as a foliar spray, molasses can act as a caterpillar deterrent. Vigorous plants in rich, well-fed soil will also have better resistance to pest infestations, making molasses a low-impact and non-toxic method of combating pests without the use of harmful pesticides.

The versatility, cost-effectiveness, and low-risk application of molasses make it a triple-threat secret weapon for growers looking to supplement their plants’ nutritional programme. It can be cheaper than most branded nutritional products and safely combined with other methods in a feeding schedule. After all, healthy plants do not need to spend valuable resources fighting infections or deficiencies and instead can focus their energies towards the high yields all growers desire.

Spoon spooning molasses from glass jar to be used for cannabis nutrients

How to Apply Molasses

Since molasses enriches both plants and soil, it can be applied throughout the growing cycle – even before the crop is planted. Soak planting soil in a solution of unsulphured molasses one week before planting to feed soil microbes. Growers can work it into their watering schedule as simply as dissolving one or two tablespoons of molasses in five litres of water. Starting with a small amount will minimise the risk of nutrient burn and avoid needlessly stressing the plant out.

Since cannabis plants will require different amounts of nutrients for each stage in their development, growers may need to alter the amount of molasses applied. Plants require potassium in molasses the most when they are flowering, as dense, resinous buds, shiny trichomes, and “loud” terpenes are the products of the water transport facilitated by potassium. It is recommended that the grower uses a higher concentration of molasses as their plants enter the flowering stage.

Molasses mixed into compost teas can be added at a ratio of 60ml for every five gallons of solution. To apply it as a foliar spray, use 5ml per gallon. It is recommended that growers use lukewarm water to help molasses dissolve completely before adding to any water or liquid fertilisers. For best results, the grower should apply it to one plant in small doses and observe the plant’s reactions before watering the rest of their crop.

There is some evidence to support that over-application of molasses may affect the taste and smoke of cannabis flowers. To avoid this, stop applications and start flushing the plants as they finish flowering (two or three weeks before harvest, depending on the strain) with water to ensure that any residual molasses is washed away.

Growers who want to bring out the best in their soils by adding molasses should also make sure the genetics they are growing are of the highest quality to take full advantage of all the love their soils receive. The genetics offered by Marijuana Grow Shop are sourced from premier seed banks and passionate commercial cultivators from around the world who have decades of experience between them.

Post author
Martin is a production horticulturist with experience in commercial cannabis cultivation and sustainable farming from his time with Emerald Cup Award-winning farmers Esensia Gardens in northern California's Emerald Triangle.
See more from Martin

More articles you would like