Does Molasses Really Help Tomato Plants? (And What Works Even Better)

What molasses really does for tomato plants—and smarter ways to improve flavor and growth.

A wooden spoon pouring molasses into a white bowl on a wooden surface — Credit:
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Whether you’re growing juicy beefsteaks, medium romas, or small cherry tomatoes, your grandmother may suggest adding molasses to the soil. The goal? This syrup is supposed to help produce a stronger, sweeter tomato crop.

However, like many old wives’ tales, this one might be overrated. Here, our gardening experts explain how molasses benefits tomato plants, whether they recommend using it, and a few other natural additives to try.

How Molasses Affects Growth

A Southern supplier once sent Siobhan Shaw, co-founder of Growing to Give, a donation of tomato fertilizer containing molasses. “We were growing food for food banks,” she recalls. “The plants we were growing in containers with this fertilizer looked strong, the leaves were vibrant, and the tomatoes developed well.”

What molasses actually does is feed soil microbes. “For home gardeners, a little splash of molasses dissolved in water near the roots once in a while can give those microbes a bit of a kick,” she says.

However, you’d save a lot of money by buying an organic fertilizer instead, says Frank Hyman, an award-winning garden designer and author of Ripe Tomato Revolution.

Molasses costs about six times as much as organic fertilizer—and has fewer types of nutrients. “So technically, molasses will help them grow, but the high cost simply doesn’t justify it,” he says. “Think about it: molasses is just made from other plants, and organic fertilizers are often made from plants and animals. Molasses isn’t a silver bullet. And there isn’t anything magical about it.”

Does Molasses Improve Taste?

As a master gardener who started out growing vegetables on a small patio, Victoria Fields has experimented with just about every old-school garden trick—including molasses. “I’d say it's a small supporting tool for soil biology,” she says. “But compost and good soil management are what really produce strong plants and great-tasting tomatoes.”

The sweetness of a tomato is mostly determined by the variety, sunlight, and balanced nutrition—especially potassium. “What molasses can do is improve overall soil health over time, which may lead to healthier plants and better fruit development,” she says. “But it’s not a shortcut for sweeter tomatoes.”

After growing thousands of pounds of tomatoes both in the ground and in containers, Shaw says the real key to stronger plants and better tomatoes is feeding the soil life, rather than just the plant itself.

“When the microbes are thriving, the plants can access nutrients more efficiently, and the fruit tends to be stronger and more flavorful,” she says. “We've grown both in the typical growing zones and in the desert, and the health of the soil plays a huge role in the flavor of tomatoes.”

How to Add Molasses to Tomato Plants

If you’re set on using molasses or have some you want to use up, Fields recommends following these steps:

Use unsulfured blackstrap molasses, as it contains more minerals—like potassium, calcium, and iron.
Mix a single tablespoon of molasses per gallon of water.
Water the soil around the base of the tomato plant. Do not spray the leaves.
Apply once every three to four weeks during the growing season.
Always apply to moist soil—not dry soil—so microbes can use it immediately.

“The key is moderation,” Fields says. “Too much sugar in soil can actually disrupt microbial balance.”

Special Considerations

Plants rely on two primary sources of energy and nutrition. The first comes from minerals, ideally supplied through a well-balanced application of organic fertilizers. These fertilizers should provide essential nutrients, such as nitrogen, phosphorus, potassium, and trace elements.

“The second source comes from soil biology," says Bob Jones, co-owner of The Chef's Garden, a family-owned regenerative farm that grows vegetables, herbs, and microgreens for culinary professionals. "This includes microorganisms such as bacteria, fungi, protozoa, and earthworms that break down organic matter and make nutrients available to plants in usable forms.”

When gardeners add molasses to soil, they’re essentially feeding these microorganisms. "However, if there isn’t already a healthy population of soil biology present, the molasses won’t have much effect," Jones says, "because there’s little life there to consume it.”

Other Natural Additives

While molasses might not be the most beneficial natural additive, there are others that will give your tomatoes a little extra boost.

Compost

A good aged compost is probably the most reliable thing a gardener can add. “It improves soil structure and gives microbes a steady food source,” Shaw says.

Lime or Wood Ash

Tomatoes evolved in a low rainfall, high pH climate. “And pH determines if a tomato plant’s preferred nutrients are available,” Hyman says. “So the right amount of lime or wood ash will act as the key to unlock nutrients in the soil.”

Kelp Meal

Kelp meal provides micronutrients and growth hormones that support fruit development, says Fields.

Eggshells or Oyster Shells

Eggshells and oyster shells are something people often overlook. “Ground finely and added to the planting hole, they provide calcium,” Shaw says, “which tomatoes appreciate, and can help prevent blossom end rot.”