Best Potassium Fertilizer For Tomatoes for Different Garden Needs

#1 · Best Overall

1. Farmer's Secret Tomato Booster

• Form: Liquid
• Weight: 8 oz

Best for: Weekly tomato feeding.

Why it ranks #1: Tomato-specific liquid lists a 3:8:7 ratio and gives weekly directions of two teaspoons per gallon, with soil or foliar application.

A 3:8:7 formula fortified with humic acid, iron, and calcium gives tomato growers a liquid feed specified for use throughout the plants’ life cycle. Its concentrated format is diluted into water, making it a fit for gardeners who want a repeatable weekly routine across tomato varieties.

The directions call for two teaspoons per gallon of water each week, so feeding can be folded into a regular watering schedule rather than applied as an undiluted product. The listing supports both foliar and soil application, offering two ways to deliver the diluted feed. Its 3:8:7 nutrient ratio and added humic acid, iron, and calcium distinguish it from a potassium-only supplement; it is a broader tomato feed for growers seeking nutrients across the full growing cycle.

Skip it if you want a potassium-only 0-0-60 product; Cz Garden Supply Muriate of Potash is listed with that analysis.

Choose this liquid for a tomato-focused weekly feeding routine that can cover foliage or soil. It suits growers who value added nutrients alongside potassium, but not those seeking a potassium-only formula or a granular application.

Listed on Amazon as: Farmer's Secret Tomato Booster Fertilizer – Super Concentrated – 3:8:7 Ratio Fortified with Humic Acid, Iron and Calcium – Grow More Tomatoes (8oz)

#2 · Best Tomato Food

2. Miracle-Gro Tomato Plant Food

• Form: Liquid
• Weight: 0.7 kg

Best for: Easy watering-can tomato feed.

Why it ranks #2: Made for tomatoes and vegetables, it feeds through a watering can or feeder every 1–2 weeks; its listed ratio is not provided.

Water-soluble tomato plant food that can be applied with a watering can or Miracle-Gro Garden Feeder makes routine feeding straightforward for vegetable growers. The listed schedule of every one to two weeks gives tomato gardeners a clear cadence, while the formula is also described as suitable for all vegetables.

The product is described as feeding instantly, and its every-seven-to-fourteen-day schedule gives gardeners a repeatable routine through the growing season. Compatibility with either a watering can or the Miracle-Gro Garden Feeder offers a choice of application workflow. The listing says it is safe for all plants when used as directed and will not burn when used as directed, supporting use across a mixed vegetable garden. It is a tomato plant food, not a stated potassium-only supplement.

Skip it if you need a stated 0-0-60 potassium analysis; Cz Garden Supply Muriate of Potash lists that ratio.

This is a practical fit for tomato and vegetable growers who want a recurring feed schedule and familiar watering equipment options. Choose it for general tomato feeding, not when a specific potassium analysis is essential.

Listed on Amazon as: Miracle-Gro Water Soluble Tomato Plant Food, 1.5 lb.

#3 · Sulfate Potash

3. FOVGOTAN Sulfate of Potash

• Form: Granules

Best for: Sulfate-of-potash granules.

Why it ranks #3: The 0-0-50 granular formula specifically lists tomatoes among its uses and supplies potassium without adding listed nitrogen or phosphorus.

A 0-0-50 sulfate-of-potash formula supplies substantial potassium in granules, giving tomato growers a solid-format option for fruiting plants. The one-pound package is also listed for houseplants, fruit, and flowers, so it can suit gardeners feeding several kinds of plants with one potassium-focused product.

The 0-0-50 analysis makes this a potassium-centered fertilizer rather than a balanced NPK feed, which can help buyers identify its role in a tomato program. Its granular form offers a different handling workflow from liquid concentrates, and the one-pound package provides a defined quantity for garden use. The listing names tomatoes, houseplants, fruit, and flowers as intended plants, making it applicable across a mixed planting rather than only a vegetable bed.

Skip it if you need explicit dilution and weekly tomato-feeding directions; Farmer's Secret Tomato Booster specifies both.

This suits growers looking for granular sulfate of potash for tomatoes alongside flowers or houseplants. Since the listing provides no application rate or schedule, it is a less guided choice for gardeners who rely on detailed feeding directions.

Listed on Amazon as: 1lb Potash Fertilizer 0-0-50, Sulfate of Potash Indoor Plant Fertilizer, Potassium Fertilizer, Plant Food for Houseplants, Fruit, Flower, Tomato, Promote Large Flower Blooming & Fruit Growth

#4 · Mineral Blend

4. Down To Earth Langbeinite

• Form: Granules
• Weight: 5.3 lb

Best for: Three-nutrient mineral potash.

Why it ranks #4: This 0-0-22 granular mineral provides potassium alongside magnesium and sulfur, and its maximum chlorine content is listed as under 3 percent.

Naturally mined langbeinite supplies potassium, magnesium, and sulfur in a water-soluble sulfate form, giving tomato growers more than potassium alone. Its 0-0-22 analysis and less-than-3-percent maximum chlorine content distinguish it from higher-analysis potash products, while the neutral pH is stated not to alter soil activity.

The three listed nutrients—potassium, magnesium, and sulfur—make this crystalline mineral a broader supplement than a potassium-only product, which may suit growers seeking all three. Its sulfate form is described as water soluble, helping nutrients enter the soil with water. The listing also states a neutral pH and maximum chlorine content below 3.0 percent, relevant details for buyers weighing soil activity and fertilizer-burn potential. The granular form comes in a five-pound package.

Skip it if you need a 0-0-60 potassium analysis; Espoma Potash 0-0-60 provides a higher listed potassium ratio.

This fits tomato growers who want potassium alongside magnesium and sulfur in a mined mineral product. Its 0-0-22 analysis is a distinct choice from high-analysis potash, so match it to the nutrients your garden needs.

Listed on Amazon as: Down To Earth All Natural Fertilizers Organic Langbeinite – 0-0-22, 5 lb

#5 · Large Potash Bag

5. Espoma Potash

• Form: Granules
• Weight: 6 lb

Best for: Ready-to-apply potash granules.

Why it ranks #5: The 6-pound granular product has a 0-0-60 analysis and is listed for vegetables; directions say apply around the drip line and water.

A 0-0-60 analysis with no sludges or fillers gives Espoma Potash a focused potassium profile for tomato and vegetable gardens. The ready-to-use granules are applied around a plant’s drip line and watered in, offering a direct soil routine without first mixing a liquid solution.

The directions allow application any time during the growing season, with spring and fall identified as best, so gardeners can plan around seasonal soil care. Spreading the granules around the drip line and watering thoroughly gives a defined placement and follow-up step. Its 0-0-60 analysis targets potassium rather than supplying a balanced NPK formula. The six-pound resealable bag provides a substantial supply for vegetable beds as well as trees, shrubs, and flowers.

Skip it if you need a balanced 8-5-5 tomato blend with added calcium; Dynamite Mater Magic lists that formula.

This suits gardeners who want a straightforward granular potassium supplement for tomatoes and other plants, with seasonal timing and drip-line directions. It is best used when potassium is the target, not as a complete NPK feed.

Listed on Amazon as: Espoma Potash 0-0-60 Potassium Fertilizer. Use for All Plants requiring Potash Supplement Including Trees, Shrubs, Vegetables and Flowers. Granular for Easy Application. 6 lb. Bag

#6

6. The Grow Co Muriate of Potash

• Form: Granules

Best for: Five-pound potash supply.

Why it ranks #6: Its 5-pound crystal-form 0-0-60 product is listed for tomatoes and other crops, but the supplied facts do not give a tomato-specific feeding schedule.

A 0-0-60 analysis in crystal-form granules gives this five-pound potash fertilizer a concentrated potassium profile for tomato growers addressing potassium needs. The listing connects potassium with sugar and nutrient transfer, and also describes support against moisture loss, making it relevant to gardens facing dry conditions.

The high-potassium 0-0-60 ratio makes this a targeted supplement rather than a complete tomato feed, while its crystal-form granules suit growers who prefer a solid product. The listing says potassium helps transfer sugars and other plant nutrients, linking the formula to plant processes beyond simple feeding. It also describes reduced moisture loss and drought resistance, a potential fit for gardens managing water stress. Protective gloves and eyewear are specified for handling.

Skip it if you need nitrogen and phosphorus in the same listed formula; Dynamite Mater Magic has an 8-5-5 analysis for tomatoes and vegetables.

Consider this for tomato growers seeking a substantial supply of high-potassium granules, particularly where moisture stress is a concern. It is a targeted potash choice, not a listed source of nitrogen or phosphorus.

Listed on Amazon as: Muriate of Potash Fertilizer, 0-0-60 NPK Ratio for Plants, 5 lbs

#7

7. Cz Garden Muriate of Potash

• Form: Granules
• Weight: 0.1 milligrams

Best for: High-potassium garden supplement.

Why it ranks #7: This water-soluble 0-0-60 potassium product is described for garden vegetables, though its directions do not provide a specific tomato dose.

A water-soluble 0-0-60 analysis puts potassium at the center of this granular plant food, giving tomato growers a concentrated supplement for fruiting and flowering gardens. Its listing also describes broad indoor and outdoor use, so it can serve vegetables alongside flowers, herbs, trees, and lawns.

The 0-0-60 analysis makes this a focused potassium choice rather than a balanced tomato fertilizer, which can suit growers looking to supplement potassium specifically. The granules are described as water soluble, giving the option to dissolve the product for application. A resealable, easy-pour package supports handling between uses. The directions advise protective gloves and eyewear, an important part of the preparation routine for anyone spreading or measuring the fertilizer.

Skip it if you want a tomato-specific liquid feed with added calcium and iron; Farmer's Secret Tomato Booster lists those nutrients.

This fits gardeners seeking a concentrated potassium supplement for tomatoes and other garden plants, especially when a granular format works for their routine. Choose a different formula if you want a tomato-specific blend with additional listed nutrients.

Listed on Amazon as: Muriate of Potash 0-0-60 Fertilizer Made in USA – MOP Potassium Plant Food for Indoor/Outdoor Plants, Flower Gardens, Fruit and Vegetable Gardens, Holistic Herbs, Trees and Green Lawns!

#8

8. Dynamite Mater Magic

• Form: Granules
• Weight: 10.88 oz

Best for: Organic tomato-bed granules.

Why it ranks #8: The OMRI-listed tomato and vegetable granules offer an 8-5-5 ratio with extra calcium, but potassium is less concentrated than in standalone potash.

OMRI-listed organic granules with an 8-5-5 analysis and extra calcium give tomato growers a broader nutrient blend for vegetables, herbs, and fruit. The directions use capful measurements worked into soil, making this a fit for gardeners who prefer preparing beds and applying solid fertilizer rather than mixing liquid feed.

For each 8-to-12-inch tomato seedling, directions call for four capfuls mixed into the top three inches of soil before planting; after 30 days, another application is specified. That staged soil routine is more involved than simply watering in a liquid, but provides clear timing and placement. The 8-5-5 analysis and extra calcium distinguish it from potassium-only products, while the OMRI listing supports buyers seeking an organic option. The granules are also listed for vegetables, herbs, and fruit.

Skip it if you prefer a liquid feed mixed into watering; Miracle-Gro Water Soluble Tomato Plant Food works with a watering can.

This fits organic-minded tomato growers preparing planting soil and following a staged granular schedule. Its broader 8-5-5 blend and extra calcium suit more than potassium-only feeding, but the application involves soil incorporation.

Listed on Amazon as: Dynamite Mater Magic – Organic Tomato Fertilizer for Bigger, Juicier Tomatoes and Vegetables, OMRI Listed, Nitrogen and Calcium-Rich Plant Food – .675 Pound Container with Shaker Lid

#9

9. TPS Nutrients Bloom Booster

• Form: Liquid

Best for: Liquid bloom and fruit support.

Why it ranks #9: This liquid phosphorus-and-potassium fertilizer is intended for fruiting plants, but the supplied facts give no NPK ratio or tomato-specific directions.

Elevated phosphorus and potassium define this liquid bloom booster, giving tomato growers a formula aimed at root development, flowering, and fruit set. Its stated use across vegetables, fruits, and ornamental flowering plants makes it an option for mixed gardens where several crops enter reproductive growth.

The high-phosphorus component is described as supporting root strength and development, while the phosphorus-and-potassium blend is also positioned for flowering and fruiting. That combination connects early plant establishment with later reproductive stages, useful for gardeners managing tomatoes alongside other crops. The liquid form offers a different format from granular potash products. However, the supplied listing does not give an NPK ratio or dilution schedule, so buyers have less specific guidance for planning applications.

Skip it if you need a stated NPK ratio and reproductive-stage directions; TPS Nutrients 5-10-10 supplies both.

Choose this liquid when your garden needs a phosphorus-and-potassium product aimed at roots, blooms, and fruit set. It fits mixed fruiting and flowering plantings, but the supplied details do not specify a ratio or dilution routine.

Listed on Amazon as: Phosphorus and Potassium Fertilizer, Liquid Bloom Booster, 8 oz

#10

10. TPS Nutrients 5-10-10

• Form: Liquid

Best for: Reproductive-stage garden feeding.

Why it ranks #10: The liquid 5-10-10 formula is suitable for garden vegetables and reproductive growth, but it is less tomato-specific than higher-ranked options.

A 5-10-10 liquid formula pairs higher phosphorus and potassium with stated directions for reproductive-stage use, giving tomato growers a guided way to feed through flowering and fruiting. It is listed for vegetables, garden beds, landscapes, and backyard growing, extending beyond a single tomato crop.

The directions specify one tablespoon per gallon of water, applied during the reproductive stage, with repeat applications as needed. That measured dilution and timing give gardeners a practical framework for use with a watering can or hose-end sprayer. Its 5-10-10 analysis includes nitrogen as well as higher phosphorus and potassium, making it broader than a potassium-only supplement. The listing connects the formula with root strength and plant structure, relevant as garden vegetables develop.

Skip it if you want a potassium-only 0-0-60 supplement; The Grow Co Muriate of Potash lists that analysis.

This suits tomato growers who want a diluted liquid feed with explicit reproductive-stage directions and flexible watering equipment. Its 5-10-10 profile is broader than potash alone, so consider whether that nutrient balance matches your garden routine.

Listed on Amazon as: 5-10-10 Fertilizer – Great for Vegetables, Tomatoes & Flowers, 8oz