The 9 Best Organic Fertilizers of 2021

An array of organic fertilizer options for your plants

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You baby your plants like you treat yourself: No synthetic chemicals and only good-for-you ingredients. Organic fertilizers depend on soil microbes to release macronutrients such as nitrogen (N), phosphorus (P) and potassium (K) gradually over time. Eventually, they improve soil structure, too. You'll see the percent of these nutrients represented in three numbers, called the NPK ratio. When it comes to fertilizers to make your plants greener, there is a dizzying array of choices with different ratios.

It’s worth noting that organic fertilizer is, well, rather stinky because it’s derived from plant and animal sources. The odor fades in a few days, but it can attract pets, who may ingest both granular or liquid forms. In fact, organic fertilizers regularly make ASPCA’s list of top 10 pet toxins because they cause vomiting, tummy upset, and seizures. Keep your four-legged family members safe by fencing your garden, not leaving product out where pets have access, and keeping container plants out of reach.

Here are our tops picks for the best organic fertilizers for targeted uses:

The Rundown
If you only want to keep one fertilizer on hand, this one has your flowers, veggies, shrubs, and trees covered.
Dr. Earth composts food grade waste instead of letting it end up in landfills.
Worm castings contain micronutrients and beneficial microbes with minimal smell.
This fertilizer has a NPK ratio of 2-3-1, so it’s a good all-purpose product that many gardeners prefer for its ease of use.
With a NPK ratio of 5-7-10, this product is specifically designed to promote heavy blooms and overall plant health.
Heavy feeders such as tomatoes use nitrogen quickly, and this product is formulated to supply plenty.
These pre-measured spikes make it easy to fertilize potted plants properly without having to mix anything.
The applicator bottle doses out just what you need to use when watering your succulent.
With a balanced 4-4-4 ratio of NPK, this granular food is pelletized for easy application and can be used on all types of grass.

Best All Purpose: Jobe's Organics All-Purpose Granular

Jobe's Organics All-Purpose Granular

This balanced fertilizer containing NPK at a ratio of 4-4-4 can be worked into the soil at planting or applied to existing plants at the drip line. It includes beneficial bacteria, fungi, and other microorganisms to boost the long-term health of your soil.

It’s ideal if you only want to keep one type of fertilizer on hand, because it’s recommended for use on vegetables, flowers, shrubs and trees. The smell can linger indoors for more than a week, so it may be best for outdoor use only.

Best Starter: Dr. Earth Root Zone Starter Fertilizer

Dr. Earth Root Zone Organic Fertilizer

If you’re planting seeds or moving transplants into the garden or containers, consider using a starter fertilizer. With a NPK of 2-4-2, the slightly higher ratio of phosphorus contributes to root establishment.

Dr. Earth, which has been creating organic products since its founding in 1991, composts food grade waste instead of letting it end up in landfills. The company is also a sponsor of the Sustainable Food Trade Association, which promotes socially responsible business practices for the organic food trade.

Best Soil Builder: Wiggle Worm Soil Builder

Wiggle Worm Organic Fertilizer

Worm castings are the digested “soil” produced by worm farming. They provide some macronutrients for leaf growth; in this case, its NPK ratio is 1-0-0. But they also contain micronutrients and beneficial microbes, and improve drainage and soil structure.

Best of all, if you’re sensitive to odors (or have pets who like to nibble!), earthworm castings don’t have a strong aroma like other organic fertilizers. They smell like rich, black garden soil. You can use these castings by adding them to the bottom and sides of the holes you dig for planting seeds or transplants, and as side dressing throughout the season.

Best Liquid: Neptune Harvest Fish & Seaweed Fertilizer

Neptune’s Harvest Organic Hydrolized Fish and Seaweed Fertilizer

This fertilizer has a NPK ratio of 2-3-1, so it’s a good all-purpose product that many gardeners prefer for its ease of use (you mix it up in a watering can). The company, which started as a wholesale fish distributor in 1965, worked with the state of Massachusetts and local universities to devise a way to utilize fish by-products from the fillet process, rather than allowing the remains to be dumped back into the ocean.

As you probably guessed, the product smells strongly of fish, but it dissipates within a day—faster than many other organic products. There’s also nothing for pets to dig up and eat, though they still may nose around the application area.

Best for Flowers: Miracle-Gro Performance Organics Blooms Plant Nutrition Granules

Miracle-Gro Performance Organics

With a NPK ratio of 5-7-10, this product is specifically designed to promote heavy blooms and overall plant health. The bottle is made from 25 percent recycled plastic, and the company launched the Parks for Pollinators program in 2017 to expand pollinator habitats in parks across the country.

Work the granules into the soil when planting, or shake on to existing plants. The shaker canister delivers an even amount over the soil surface.

Best for Tomatoes and Vegetables: FoxFarm Happy Frog Tomato & Vegetable Fertilizer

Fox Farm Happy Frog Tomato and Vegetable Fertilizer

Heavy feeders such as tomatoes use nitrogen quickly, and this product is formulated to supply plenty, with NPK at a 5-7-3 ratio, as well as calcium to fend off blossom end rot. Blossom end rot is a nutrient deficiency which causes your tomatoes look perfect on top, but then turn ugly black on the bottom.

Beneficial fungi also is included to help build healthy soil. Use the granules in containers or in-ground plantings.

Best for Houseplants: Jobe's Organics Fertilizer Spike All Purpose

Jobe’s Organics All Purpose Fertilizer Spikes

Overfeeding houseplants can cause them to develop spindly growth or become more vulnerable to pests and diseases. These pre-measured spikes, with a balanced 4-4-4 formula, make it easy to fertilize properly without having to mix anything.

Stick one in the pot (or several for larger pots) for no-mess feeding. The odor is almost non-existent, which makes them a better choice for indoor feeding. You’ll use them every eight weeks during the active growing season, which is spring to fall for most houseplants.

Best for Succulents: Espoma Cactus! Succulent Plant Food

Espoma Cactus! Organic Succulent Plant Food

Although succulents typically don’t need coddled, which is why so many people love them, they can benefit from feeding during their active growth period in the spring or summer. This applicator bottle doses out just what you need to use when watering.

While the 1-2-2 NPK formula is on the stinky side, the odor doesn’t linger long. The company’s products are approved for organic use by the California Department of Food and Agriculture (CDFA), and their factory is 100 percent solar powered with an emphasis on zero waste manufacturing.

Best for Lawns: Kellogg Garden Organics Lawn Food

Kellogg Garden Organic Plus Lawn Food

Here at Treehugger, we're big fans of lawn alternatives, but if you do have grass to feed this organic fertilizer will do the trick. With a balanced 4-4-4 ratio of NPK, this granular food is pelletized for easy application and can be used on all types of grass. It’s safe to walk on immediately after applying, and it greens up lawn without burning grass.

The company, founded in 1925, is the first and only company that has all its branded soils and fertilizers registered with both OMRI and the California Department of Agriculture’s Organic Input Review.

Final Verdict

Our top pick for an all-around good organic fertilizer is Jobe’s Organics All-Purpose Granular Plant Food (available at Lowe's). If you’re looking to build your soil, consider picking up a bag of Wiggle Worm Soil Builder Earthworm Castings (available at Amazon).

What to Look for in Organic Fertilizer 

Organic Certification: The term “organic” is not regulated for fertilizers, so essentially anyone can put it on the label. Look for products with the Organic Materials Review Institute (OMRI) seal, an independent, nonprofit organization that certifies which products are compliant with USDA organic farming standards.

Liquid vs. Granular Fertilizer: Granular types take longer to break down, while liquid gives a quick nutrient boost. Many gardeners use both types, but make sure you’re not overdoing it. Applying excess fertilizer–even one that’s organic–can pollute water supplies. Get a soil test every three years to monitor what your garden actually needs; your university county coop extension can perform one, typically for about $20 (find yours here).

NPK Ratio: Different plants have different nutritional needs, but the main ones to pay attention to are nitrogen (N), phosphorus (P) and potassium (K). It’s a good practice to look up the recommended NPK ratio for the plants you want to fertilize, and shop accordingly. 

Good to Know

Composting is another great way to make your own fertilizer. It does take some time and effort, but composting offers huge environmental benefits in terms of building soil, reducing landfill and even preventing planet-heating greenhouse gas pollution. Learn more about how to get started composting here.  

There are also many things in your kitchen that can serve double-duty as plant fertilizer, from eggshells to banana peels. But before you start dumping coffee grounds onto the closest plant, but you’ll need to learn about the kinds of nutrients the plant species in your garden need and what different kitchen cast-offs offer. Check out our guide to making homemade plant food. 

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Author Arricca SanSone has many years of experience writing about homes and gardens.