Benefits of Adding Molasses to Your Fertilizer Regimen

By Harley Smith
Published: November 29, 2022
Key Takeaways

Adding a little cane molasses to your fertilizer regimen could result in a myriad of benefits for your plants. Here’s why.

Many gardeners are discovering the benefits of adding a little cane molasses to their fertilizer regimen.

Some people think that the cane molasses is food for the plant, but that isn’t really true. Plants cannot take up large organic molecules. Complex organic molecules must first be digested by micro-organisms in the soil before they can be taken up by the plant. That’s why certified organic fertilizers are not usually recommended as the sole source of nutrients for hydroponics. More often than not it would just make a muddy mess! But in soil, there are plenty of spaces for micro-organisms to colonize and make their homes, and plant roots are teaming with microbes.


How Plants Make and Use Sugars

illustration of the photosynthesis processPlants make most of their own sugars in a process called photosynthesis.

Think of it this way: organic fertilizers feed the micro-organisms in the soil, and micro-organisms feed the plant. It’s the same way with the complex carbohydrates in molasses.

Plants can’t take up large sugar molecules directly. If and when they do take up complex sugars, plants actually have to expend energy in the process. Instead, plants make most of their own sugars in a process called photosynthesis. When bathed in the energy of full-spectrum light, plants are able to knit molecules of water and carbon dioxide together to make sugars.

Some of the sugars are used as carbon skeletons for building plant tissues, and some of the carbohydrates are burned to produce quick, available energy for growth, reproduction and cellular repair. Excess carbohydrates are stored for later use, or leaked from the roots to feed beneficial bacteria and fungi in the root zone. In some cases, as much as 30 to 50% of the energy of photosynthesis is leaked by the plants to feed the soil-borne microbes.


Benefits of Molasses in Gardening

bacteria or microbes in soilHealthy microbial populations in the soil stimulate root growth.

Molasses not only provides a good carbon source for rapid microbial growth, it’s also a good source of iron for plants. Iron is easily locked up in the soil, and it is often the limiting factor for plant growth. But some plant growth-promoting bacteria make special organic molecules called siderophores. The word siderophore literally means iron carrier. It is one of the best chelators of iron found in nature.

As the soil bacteria eat the molasses, the iron in the molasses remains soluble and available to the plants. The results? Better color, increased photosynthesis, greater stress tolerance and sweeter fruit. Many scientists attribute most of the benefits of molasses supplements directly to the greater availability of iron to the plant. Another indirect benefit of molasses is speeding up the availability of organic nutrients.

Although micronized molasses has practically no nitrogen, phosphorus, or potassium, the micro-organisms it feeds can dramatically improve nutrient availability. Some micro-organisms fix nitrogen directly from the air and process it into plant-available form.


Other bacteria and fungi make the phosphorus that is locked up in the soil soluble and feed it to the plant. Some microbial byproducts improve the uptake of calcium, and other micro-organisms mobilize potassium.

Best of all, during carbohydrate metabolism, microbial cells make organic acids that chelate many essential trace elements such as iron, copper, manganese, and zinc, making them readily available for plant uptake. Trace elements activate many powerful enzymes, energizing the chemistry of life. Micronized molasses definitely has its place in the organic garden. As beneficial micro-organisms feed on the sugars, they multiply and divide, and in the process they exude many enzymes and co-enzymes.

Soup Up Your Soil with Kelp, Molasses, and Guano
How Living Soil Benefits Cannabis: The Microbes Behind Healthy Plants
The Importance of Brix in Cannabis Health


How and When to Use Molasses in the Garden

compost teaUse molasses to sweeten your irrigation water or compost tea.

Micro-organisms may be thought of as living biostimulant factories, producing growth hormones, amino acids, B-vitamins, organic acids and other powerful growth factors that benefit plants. As more is discovered about the benefits of plant growth-promoting rhizobacteria, there is new interest in making compost teas and other microbial inoculants.

For example, during their establishment phase, plants are sometimes limited in their carbohydrate production and may not be able to exude enough carbohydrates to support a strong microbial base. Composts supply both carbon and nitrogen, but sometimes they are released too slowly, or they don’t remain in balance with the needs of the plants.

Water soluble carbohydrates such as micronized cane molasses are an excellent carbon source when making compost teas. Spoon-feeding your plants with water-soluble molasses or drenching the roots with molasses-infused compost tea can help adjust the carbon-to-nitrogen ratio and boost the microbial populations in the soil that stimulate root growth when plants need it the most.

During the later stages of fruiting and flowering, molasses supplements may show their greatest benefits. Plants tend to get stingy with their carbohydrates during heavy fruit and flower production, preferring to store them in their fruits and seeds instead of leaking them from their roots. So in nature, micro-organisms in the root zone begin to go dormant towards the end of the growing season. A boost of carbohydrates can revive the dwindling microbial populations.

Carbohydrate supplements are also beneficial when flushing excess mineral salts from the root zone. Simply add a little cane molasses to water and use it in your soil drench, preferably with a little yucca extract.

Microbial populations can also suffer after times of stress. For example, over-fertilizing or poor water management not only affects plants, it can seriously harm beneficial micro-organisms in the soil. A spoonful of molasses can go a long way to help the colonies of beneficial micro-organisms re-establish themselves, and may even help the plants recover more quickly. Remember, though, moderation is the key. Too much molasses can cause a bloom of micro-organisms that can actually compete with the nutritional needs of the plant.

If you don’t want the sticky mess of pouring and measuring thick liquid molasses, then powdered molasses is for you. Soluble-grade, micronized molasses is a powdered product that maintains the quality and consistency of liquid molasses, but adds the handling and storage characteristics of a dry product. During the manufacturing process, 10 lbs. of cane molasses is reduced to 1 lb. of soluble concentrate, making it much easier to handle and store. It’s so concentrated that it only takes about 1/8 to ¼ tsp. per gal. to sweeten your irrigation water or compost teas.

So there you have it, the basics of feeding your garden cane molasses. A boost of this plant supplement will energize the life in the soil and help your plants stay productive until the day of harvest.


Share This Article

  • Facebook
  • LinkedIn
  • Twitter

Written by Harley Smith

Profile Picture of Harley Smith
Harley Smith is the director of research for NPK Industries. A veteran in the hydroponics industry, Harley has more than 18 years of consulting and educating experience. He is regarded as an expert on plant nutrition and organic bio-stimulants, performing research and new product development in the US and Europe.

Related Articles

Go back to top
Maximum Yield Logo

You must be 19 years of age or older to enter this site.

Please confirm your date of birth:

This feature requires cookies to be enabled