Updated: Sep 15, 2020
Horticultural molasses has several uses in the garden, as we’ll explain. Since molasses is a type of sugar, it provides food for microbes and other microscopic organisms living in the soil that help break down organic matter. It’s generally considered to be the best type of sugar to use on your garden. Because it increases microbial activity, it’s often used to help rebuild soil that’s been depleted by synthetic fertilizers.
Dry Molasses Vs. Liquid
Horticultural molasses is available in either dry form or liquid. Dry Molasses is actually dried grain hulls, peanut shells, or other organic “carrier” material that has been sprayed with liquid molasses to create an easy-to-spread sugar. The hulls themselves also offer some fresh organic matter for other organisms essential to the decomposition process. It’s easy to apply with a fertilizer spreader to your lawns and beds, and you can apply it as often as once a month at a rate of 20 lbs per 1000 square feet. Dry Molasses can also be combined with your granular fertilizer and applied together.
Foliar Spraying and Soil Applications
Molasses is also available as a liquid. While the liquid product doesn’t last as long as the dry version, it makes an effective compost accelerator, foliar spray, and even as a tree stump remover. A number of popular liquid fertilizers include molasses as a key ingredient.
For compost piles, use the liquid to help accelerate the decomposition of organic matter. Spraying it on plants will increase sugar levels, which can improve resistance to chewing and sucking insects. For general foliar feeding, use 1 and 1/2 tablespoons per gallon of water. Spray every seven to 10 days during the growing season.
As a soil amendment, mix 2 to 3 tablespoons per gallon of water. Shake well before each use. Apply it with a pump sprayer or hose end sprayer about every 10 days. One gallon covers 8,000 square feet. Do not apply when outside temperature is above 90 degrees F. Clean sprayer after each application.
Stump and Root Drenching
Liquid Molasses is also a great for removing tree stumps, unwanted woody plants, tangled roots, and other tough-to-dig-out plants. The molasses causes the plant material to rot away, leaving you with healthy, fresh, well composted soil!
First dig a moat around the plant or stump to be removed. For large stumps and trunks, drill a few holes in the wood to create additional cavities to hold the molasses. Fill the entire moat and other cavities with liquid molasses, then back fill it with dirt or mulch. The sugar in the molasses will cause the roots of the plant to rot.
This method can take anywhere from a few weeks to many months depending on how thick and extensive the trunk and root system are. Check on your work every 3 months and repeat the process as necessary.
CAUTION: Applying a large amount of molasses close to your desirable trees or plants can harm their roots as well as those of the ones you are trying to eliminate.
Molasses is also an ingredient in many fire ant mound drenches and is used to control other insects as well.
Wet or dry, molasses is a useful multi-purpose product that should be in every organic gardener’s tool shed.