Top 7 Best Fertilizer for Watermelon: Reviews and Complete Guide

The best fertilizer for watermelon proves to immensely help your watermelon growing process. But, not all fertilizers are created equally.

The differences between the best and average fertilizers are drastic. It means whether your fruits are juicy, sweet, bland, or pale, depending on the product.

Our watermelon fertilizer recommendation is the Miracle-Gro Continuous Release Plant Food. This product can feed microbes that will break down natural ingredients, making your fruits stronger and increasing water efficiency.

Miracle-Gro Shake 'N Feed Tomato, Fruit & Vegetable Plant...
9,331 Reviews
Miracle-Gro Shake 'N Feed Tomato, Fruit & Vegetable Plant...
  • Contains natural ingredients to feed microbes in the soil
  • Specially formulated with micronutrients to help plants grow...
  • Feeds up to 3 months

Besides, the producer only uses natural ingredients. Thus, the fertilizer is incredibly safe for your health.

Particularly, it is best regarding the Calcium content. This feature makes watermelons have a strong cell wall, protecting them from many diseases, such as Calcium deficiency.

The Top 7 Best Fertilizer For Watermelon

Miracle-Gro Continuous Release Plant Food: Best Overall

Miracle-Gro Shake 'N Feed Tomato, Fruit & Vegetable Plant...
9,331 Reviews
Miracle-Gro Shake 'N Feed Tomato, Fruit & Vegetable Plant...
  • Contains natural ingredients to feed microbes in the soil
  • Specially formulated with micronutrients to help plants grow...
  • Feeds up to 3 months

This product does not have any adverse effect on human health as it contains 100% natural ingredients. These components can feed microbes in the soil, improving both watermelon plant fitness and production.

Microbes will break down natural ingredients, helping your watermelon plants to grow stronger. Besides, they can also help increase the water efficiency.

The cell walls are important to watermelon fruits since once it is broken, your fruits will become inedible. The product has Calcium that helps form stronger walls and long-lasting fruits.

Besides, many edible crops are likely to suffer disorders commonly associated with Calcium deficiency. This fertilizer with an added amount of Calcium can be conducive to the prevention of these diseases.

What we like

  • Increases water efficiency
  • Prevents disorders
  • Boost stronger cell walls

What can be improved

  • Poor packaging

Osmocote Smart-Release Plant: Best For Smart Crops

Osmocote Smart-Release Plant Food Flower & Vegetable, 1 lb.
19,737 Reviews
Osmocote Smart-Release Plant Food Flower & Vegetable, 1 lb.
  • OSMOCOTE’S DIRECTIONS FOR USE: 1 lb. covers 40 sq. ft....
  • OSMOCOTE QUALITY: Osmocote is the original slow-release...

Osmocote consists of a nutrient granule coated with semi-permeable resin. Once you apply them, water will penetrate the granule and dissolve the nutrients.

The unique resin coating can react at relatively low soil temperature.

This product’s nutrient content is 14-14-14. Thus, it is suitable for early season start. The product will promote vigorous top-growth and strong root development.

The fertilizers’ formulation is particularly for growing flavorful vegetables and colorful blooms. It is unfortunately not too helpful when you want your plants to produce more fruits.

You don’t have to use the fertilizer constantly because it can last up to four months; you won’t need to worry about spending your budget for a long time.

What we like

  • Smart and convenient packaging
  • Beautiful flowers and bountiful vegetables
  • Strong root development
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What can be improved

  • Not help the fruit production

Jobe’s Organics Fruit & Citrus: Best For Being Eco-friendly

Jobe’s Organics, 09226NA, Granular Plant Food, Fruit &...
14,024 Reviews
Jobe’s Organics, 09226NA, Granular Plant Food, Fruit &...
  • Package contains 4 Pounds organic fruit and citrus...
  • Plant fertilizer is formulated with a 3-5-5 NPK to provide...
  • Jobe's organic fertilizer contains no synthetic chemicals...

If you are environment-conscious, you can opt for the Jobe’s Organics. These fertilizers are renewable, biodegradable, sustainable, and friendly for the environment.

The manufacturer combines healthy bacteria, Mycorrhizal fungi, and Archaea in this product, helping produce long-term benefits without synthetic chemicals and creating a healthy ecosystem.

The Archaea can clean the soil, returning it to a more natural state, while Mycorrhizal fungi expand the surface-absorbing area of the watermelon roots by 100 to 1000 times.

This feature increases root mass and promotes plant growth.

Besides, the Jobe’s Biozome are extremely aggressive microorganism Archaea that will produce nutrients quickly, allowing you to enjoy a faster result.

However, because the product utilizes fungus, there will be an unpleasant odor. Some people cannot stand this smell.

What we like

  • Environmentally-friendly
  • Increases root mass
  • Fast result

What can be improved

  • Unpleasant smell

Dr. Earth Organic Tomato, Vegetable & Herb Fertilizer: Best For Safety

Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer Poly...
7,807 Reviews
Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer Poly...
  • For more nutritious and tasty vegetables
  • Optimum levels of primary plant nutrients
  • Contains no GMOs, chicken manure or sewage sludge

The product does not use synthetic chemicals, chicken manure, or toxic ingredients. It means that Dr. Earth is safe for pets and humans.

This fertilizer contains proteins, multi-minerals, humic acids, carbohydrates, and trace elements, all of which promote the healthiest vegetables for your family.

More interestingly, the product is verified by the OMRI, OIM, CCOF, and Non-GMO Project. Therefore, you can put your mind at rest about its safety.

It contains probiotic, 7 champion strains of beneficial soil microbes plus ectomycorrhizae and endomycorrhizae, enhancing nutrient availability and plant performance. So, this vegetable plant food is good for the initial planting of seeds, transplanting, top dressing or compost tea.

However, the fertilizer can encourage the growth of small fungus gnats, resulting in your plants suffering from powdery mildew.

What we like

  • Pet and human-friendly
  • Non-GMO Project verified
  • Nutrient enhancement

What can be improved

  • Potential small fungus growth

Fox Farm Instant Concentrate Grow Big Liquid Fertilizer: Best For Plant Size

Fox Farm FX14092 Grow Big Liquid Concentrate Fertilizer,...
3,652 Reviews
Fox Farm FX14092 Grow Big Liquid Concentrate Fertilizer,...
  • Get your garden going with grow big, Foxfarm's liquid...
  • Grow big contains earthworm castings, Norwegian kelp and...
  • Garden tip: allow new plantings a few days to settle in,...

The product has earthworm castings, Norwegian kelp, and essential micronutrients. This feature is beneficial for plant size and structure enhancement, giving more abundant fruit, flower, and bud developments.

Because this pick is a liquid concentrate fertilizer, you can use it for foliar feeding, applying to both sides of the leaves without causing any damages.

This product requires you to use it at the rate of 2 teaspoons per gallon of water every other time you water, preferably in the early morning.

One drawback is the sediment on the bottom, misleading you to use improper doses. Thus, it is advisable to shake the bottle vigorously before every use.

What we like

  • Increases plant size
  • Used for both sides of leaves without damages
  • Low usage rate

What can be improved

  • Misleading sediment on the bottom

Earthworm EarthPods Premium Fruit & Citrus Plant Food: Best For In- and Outdoors

EarthPods Premium Fruit & Citrus Plant Food – Easy Organic...
1,761 Reviews
EarthPods Premium Fruit & Citrus Plant Food – Easy Organic...
  • FAST & EASY TO APPLY — Push 1 EarthPod all the way into...

This fertilizer can boost watermelon flower production and leaf growth, thanks to its premium break-through formulation.

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The Earthworm plant food provides minerals, natural nutrients, growth hormones, and beneficial microbes to replicate forest earth composition. It, therefore, can enhance melon leaf color and blossoms.

This intricate system can also help reduce transplant shock, build resistance to fungal disease, pests, or drought and enhance seed germination.

Another plus point is that it can be used both indoor and outdoor because of its eco-friendly and compact features.

You can push one EarthPod into the potting soil mix near the center of the fruit plant, then water. The capsule will break down and slowly release nutrients directly to the root zone.

What we like

  • Compact
  • Easy application
  • Flower and leaf booster
  • Both indoor and outdoor uses

What can be improved

  • Slow result

Burpee Organic Tomato and Vegetable Granular Plant Food: Best For Easy-to-use

Burpee Organic Tomato & Vegetable Granular Plant Food, 4 lb
16,506 Reviews
Burpee Organic Tomato & Vegetable Granular Plant Food, 4 lb
  • Burpee Organic All Purpose Granular Plant Food is formulated...
  • The easy-to-apply granules release essential nutrients...
  • Contains nutrients, plants will produce superior results...

When you want something more easy and effortless, you can rely on this Burpee product. You can simply release the granules, which will then immediately provide nutrients to the plants.

Furthermore, the product can continuously offer a stream of plant food for up to 3 months, allowing green foliage all season long and succulent fruit at harvest time.

This vegetable plant food also contains beneficial microbes and nutrients to improve the soil quality and promote robust roots.

However, the customer service is poor. Some customers say that they receive expired products, whereas some claim they receive opened bags.

What we like

  • Easy-to-use
  • Long-lasting effect
  • Robust root improvement

What can be improved

  • Poor customer service

Fertilizer Buying Guides

Watermelon Fertilizer Schedule

To know what is the best fertilizer for watermelons, you may need to have a basic understanding of how to fertilize watermelon and when to fertilize watermelon.

Initially, you should place the seeds indoors for up to 20 days before planting them in the garden. The soil condition should be at warm temperatures between 80 and 85 degrees Fahrenheit, moist, and full of bright light.

Then, watermelon seeds need to be located outdoors in the spring. For the best germination, the environment should be warm soil at around 70 degrees Fahrenheit.

To prevent Nitrogen burn, you should blend the fertilizer with the top six inches of the soil. Compost helps improve the soil structure and allows micronutrients in the mix and soil moisture.

You can deliver mulch around the watermelon plants for water retention, preventing weed growth and giving Nitrogen-rich organic matter to the soil.

It is advisable to wait until the vines begin to spread out. If you’re using a granular fertilizer, you can choose a balanced one like a 10-10-10 or 5-5-5.

Then read the label and follow the manufacturers’ instructions for the exact dosage. You can use it at the rate of 1/2 pounds per 100 square feet.

You should scatter the fertilizer around the watermelon plants and water evenly. It’s crucial to ensure that the fertilizing product is not exposed to the plant because it may cause burns.

If you use a water-soluble type fertilizer, you can use a 1-gallon jug to mix the fertilizer, then leave it at the main stem’s base.

After the blossoms appear and the fruit begins to set, you can apply the second fertilizer. This process will help ensure the fruit has enough energy to produce fruits.

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For the plants to absorb the most nutrients and water to their roots, you can apply fertilizer with a higher amount of Phosphorus and Potassium when the fruits are maturing.

In some regions, people also add fertilizer to the soil a few days before they plant. People scatter a balanced granular fertilizer in the watermelon patch, along with some lime for preferable conditions.

After that, they switch to a water-soluble fertilizer for the rest of the season.

Reading Fertilizer Numbers

There are three numbers on a fertilizer package. They will inform users about the percentage of available primary macronutrients by weight in the package.

  • Nitrogen (N) content.
  • Phosphorous (P) content.
  • Potassium (K) content.

The pack with 15-5-10 means 15% nitrogen, 5% phosphorous, and 10% potassium. To determine each bag’s amount, you will multiply the percentage by the bag’s weight.

For example: when the bag weighs 50 pounds, the amount of each component is:

  • 0.15 x 50 = 7.5
  • 0.05 x 50 = 2.5
  • 0.1 x 50 = 5

Thus, the bag contains 8 pounds of nitrogen, 2 pounds of phosphorus, and 4 pounds of potassium.

The rest is inert material, which helps fertilize the watermelon evenly and prevents chemical burn.

Best Fertilizer N-P-K Ratio for Watermelon

An application of nitrogen can lead to excessive foliage growth rather than the melon development. This food plant type will nourish the vine rather than the fruits.

Fertilizers that have more potassium and phosphorus are ideal for melon production. When the watermelons are in the early stage of growth, it is more beneficial for them to use the high nitrogen fertilizers.

Once you are ready to transplant or the seedlings are set, it would be more conducive to top dress with an NPK formulation ratio of around 1-1-1. You can also apply 5-5-5 or 10-10-10 general all-purpose fertilizer.

When fertilizing watermelons, it’s necessary to ensure that the fertilizer does not touch the leaves. The leaves are sensitive and can be damaged upon exposure to fertilizer.

You can use fertilizer one time before planting the seed or when transplanting a watermelon seedling. Fertilize one more time when the vines start to ramble and another time when the watermelons are set.

Types of Watermelon

Black Diamond Watermelon:

  • The fruits can exceed 50 pounds in weight. Thus, they require a lot of garden space.
  • The Black Diamond Watermelons’ rinds are tough and hard.
  • These plants require a minimum of six hours of sun each day.
  • The soil must be well-drained.

Charleston Gray Watermelon:

  • It is considered one of the best American watermelons ever produced.
  • This type of watermelon has a bright red flesh with a juicy and sweet taste.
  • The weights are between 20 and 40 pounds.
  • Charleston Gray Watermelon requires plenty of sunlight.

Crimson Sweet Watermelon:

  • The disease-resistant features make growing this watermelon breed much easier. Thus, if you are a starter, you may have an easier time planting them.
  • The Crimson Sweet watermelon fruits are commercially popular. It is because of their firm and sweet flesh.

What is the Best Environment for Watermelon?

To plant the seeds, you may need fertile and well-tilled soil. You can use compost or manure to create soil amendments. This homemade garden fertilizer helps to raise the nutrient level in the ground.

There should be sharp sand for proper drainage. People usually add a continuous boost of nutrients by applying a slow-release fertilizer into the soil.

The slow-release fertilizer can help reduce your maintenance and labor during the growing season.

You can place your fruits in a site with full-sun exposure. The environment should be warm and humid microclimate


In conclusion, the best fertilizer for watermelon plants is the Miracle-Gro Continuous Release Plant Food. It helps increase water efficiency, avoid potential diseases, and offer stronger cell walls.

To sum up, to find the best fertilizer for watermelon, you may need to read the label, track different fruit growth stages, and choose the product that fits your melon types. All necessary information can be found in the concise buying guide above.

Last update on 2024-05-09 / Affiliate links / Images from Amazon Product Advertising API

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Jill Sandy

I am a sustainable focus gardener. I love decorating my home backyard with beautiful landscape design and creative garden care techniques I develop myself.