Feed your plants and build great garden soil with these high-quality organic fertilizers.
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All plants need nourishment. In nature, plants cooperate with microorganisms like fungi and bacteria to scavenge nutrients from a variety of sources, including the organic and mineral content of the soil and gases in the atmosphere. Under cultivation, these systems are not as robust. Domestic plants, from lawn grass to houseplants, need a little help to grow their best. That’s where fertilizer comes in.
Organic fertilizers stimulate and support the natural processes plants use to feed themselves. The fertilizer feeds soil-dwelling microorganisms that then deliver the nutrients to plants. Over time, they increase soil organic matter which leads to improved soil aeration and water-holding capacity, as well as a better physical growing environment. The best organic fertilizer options have an optimal NPK ratio (percentage by volume of nitrogen, phosphorus, and potassium) for the plants to thrive.
Organic fertilizers come from natural ingredients like plant scraps, animal waste, and minerals. Some are liquids, and others are dry. They have minimal processing, are easy to apply, and have a consistent texture throughout the package. The best organic fertilizers can make your edible or ornamental plants healthier by having a balance of nutrients, quality ingredients, and the most appropriate application or use for your plants’ needs.
Our Top Picks
Several big brands offer excellent organic fertilizers, so it can be tough to choose. These recommendations consider the products’ nitrogen-phosphorus-potassium (NPK) analysis, ingredients, application method, and effectiveness in each category.
Jobe’s Organics 09524 All Purpose Granular Fertilizer is a fast-acting and balanced (4-4-4 NPK) fertilizer made from feather meal, bone meal, processed poultry manure, and sulfate of potash. It also includes multiple strains of beneficial archaea, bacteria, and fungi that quickly facilitate the transfer of nutrients to plants. Over time, these microbes work with the plant to improve the surrounding soil structure. This is a great regular maintenance fertilizer for annuals, perennials, edibles, trees, and shrubs, and almost all outdoor gardens.
Be aware that excessive odor can be detected with this product. You can minimize the odor by mixing this fertilizer with soil, not applying it on the surface. Other possible side effects of using organic fertilizers include superficial fungal growth on the soil surface and attraction to worms and insects, neither of which are bad for plants.
Espoma Plant Tone is a slow-release 5-3-3 fertilizer derived from feather meal, poultry manure, cocoa meal, bone meal, cottonseed meal, greensand, humates, sulfate of potash, and sulfate of potash magnesia. Added beneficial microbes activate in the soil to increase the fertilizer’s efficiency and improve soil structure. This fertilizer is an excellent general-purpose choice for season-long use on flowers, vegetables, trees, and shrubs.
This Espoma product is not meant for houseplants unless they will spend several weeks outdoors. The fertilizer is high quality but can have a bit of a smell. Mixing it into the soil minimizes the odor. Store any unused portion in a sealed container to avoid attracting animals with the scent.
Milorganite 0636 Organic Nitrogen Fertilizer is a slow-release 6-4-0 NPK fertilizer composed of heat-dried microbes that have digested the organic matter in wastewater. Milorganite has been used to maintain golf courses for nearly a century. Their slow-release formula, including 4 percent iron, stimulates strong root development and deep green growth for up to 10 weeks. The product won’t burn grass and it is factory tested daily for compliance with EPA standards.
This slow-release product requires a little patience. It takes 8 to 10 weeks to see the full effect when using this fertilizer to rejuvenate a lawn. Other factors like soil pH, water, diseases, and insects also affect how green a lawn looks and if a fertilizer like this doesn’t result in a greener lawn, have the soil tested by your county’s Cooperative Extension Service. Also, bear in mind that fertilizer alone does not cause grass to grow into bare patches. You might have to sow seed or lay sod in addition to fertilizing.
Neptune’s Harvest Organic Fish & Seaweed Fertilizer is a 2-3-1 NPK fertilizer made from North Atlantic fish and seaweed. This convenient liquid concentrate can nourish most types of plants, indoors and out. Simply mix the concentrate with water according to the label directions and apply it to the root zone. A little goes a long way—houseplants use 1 tablespoon per gallon of water. Outdoor plants use 1/8 cup per gallon of water. The high phosphorus ratio stimulates deep root growth while boosting flower and fruit quality.
This is a concentrated fish-based fertilizer, so the undiluted concentrate has an odor, but the smell fades quickly, even when used on indoor plants. Check the package for damage or leaks upon arrival and handle the product with gloves while diluting the concentrate.
Jobe’s Organics All Purpose Fertilizer Spikes deliver 4-4-4 NPK plant food directly to the plant’s root zone. They eliminate the mess of handling fertilizer with no required measuring or mixing. Use the 50 included spikes for indoor or outdoor containers, or in planting beds. In spring or early summer, insert the required number of spikes (based on container size or square feet of bed space) around each plant, and that’s it. The fertilizer gradually breaks down to feed the plant throughout the growing season. Beneficial microbes in the formula help to break down the fertilizer for plants, increase soil organic content, and boost plant disease resistance.
Be sure to fully insert the spikes into the soil and cover them after installation. The beneficial microbes include several species of mycorrhizal fungi that can appear as fuzzy white growth if not completely buried.
Espoma Organic Bio-Tone Starter is a 4-3-3 NPK fertilizer derived from feather meal, poultry manure, bone meal, alfalfa meal, greensand, humates, sulfate of potash, and sulfate of potash magnesia, plus 13 species of beneficial microbes.
Bio-Tone is unique in its incorporation of humates, complex organic molecules formed within the earth during the decomposition of ancient plants and animals. They neutralize the soil and improve nutrient uptake of plants. The beneficial microbe mix in Bio-Tone includes 10 species of fungi that work in conjunction with plants to increase root mass by up to 30 percent, and healthy roots give plants the best start.
The nutrient mix includes 2.4-percent slow-release nitrogen for an extended feed time. Use this fertilizer at planting time for all outdoor plants and when repotting houseplants. Be sure to mix thoroughly with the soil to eliminate the smell. Some superficial fungal growth might appear on the soil surface after planting but is not of concern.
Dr. Earth 707P Organic Bud & Bloom Fertilizer is a 3-9-4 NPK fertilizer made from fish bone meal, alfalfa meal, feather meal, soft rock phosphate, and mined potassium phosphate. The high phosphorus content provides ideal conditions for flowering and fruiting plants, including bulbs and rhizomes. No chicken manure or wastewater sludge means no bad smell.
This fertilizer has excellent microbe content, with more than 20 strains of beneficial bacteria and fungi to boost plant immunity and increase nutrient efficiency. Mix this fertilizer into the soil before planting for quick root establishment and heavy yields of flowers and fruit. The Dr. Earth fertilizer is primarily manufactured for dry application, to be incorporated into the soil ahead of planting or as a maintenance fertilizer for established plants. The label includes directions for making a fertilizer tea as well, which might be beneficial for fruit growers.
Wiggle Worm Organic Soil Builder is made of 100-percent screened worm castings, with no wood chips or other filler. Earthworms are high-level soil builders that consume large quantities of rich organic material. The raw materials in the Wiggle Worm soil builder contain a variety of minerals and trace elements. The worms digest the materials to chemically and physically convert them into a fertile soil amendment. The end product improves soil’s water-holding capacity and aeration. It also includes a diversity of beneficial microbes that contribute to root development and boost overall plant health and vigor.
This product contains 1 percent nitrogen, 0.9 percent of which is delivered slowly, plus 1 percent calcium and 0.2 percent iron. Use it in combination with local soil for planting trees, shrubs, and flowers. Sprinkle it into seed furrows before planting vegetable seeds. It can also be added to the soil surface of houseplant containers.