Organic Fertilizers for the Garden

Categories|Soil and compost
Organic Fertilizers for the Garden

Yearly applications of compost will provide most of the nutrients that your plants need. But you may occasionally want to give your plants a boost with an organic fertilizer.

Organic Fertilizers

Understanding the numbers

Fertilizers have three numbers on the bag. Those three numbers represent the amount by volume of the nutrients your plants need the most:  nitrogen, phosphorus, and potassium.

NPK = Nitrogen – Phosphorus – Potassium.

For example, a bag that says 5-4-3 has 5% nitrogen, 4% phosphorus, and 3% potassium.

Each nutrient serves a different function for your plants. The easiest way to remember what each nutrient does is “up, down, all around.”

Nitrogen is “Up.” It encourages leafy, green growth.

Phosphorus is “Down.” It encourages healthy root systems, and also fruiting and flowering.

Potassium is “All Around.” It’s valuable for the overall health of the plant, including fruit formation and hardiness.

Common organic fertilizers


Organic fertilizers make plants AND pollinators happy!

Organic fertilizers are those that contain carbon, plus one or more nutrients other than hydrogen and oxygen required for plant growth. We’ve listed some common organic fertilizers here, along with their estimated N-P-K. Always check the bag for the specific nutrients by volume, and use according to directions.

Bloodmeal (12-0-0). Derived from blood, bloodmeal is a quick-acting source of nitrogen that encourages leafy growth. You can also add it to your compost heap to help speed decomposition.

Bonemeal (4-12-0) Made from ground bones, bonemeal is a slow-release source of phosphorus and calcium. Throw some into the planting hole when planting bulbs.

Cottonseed meal (6-2-1) A good fertilizer for acid-loving plants like blueberries, cottonseed meal also acts as a soil acidifier. Be sure to get one that is certified pesticide free.

Egg shells (1.2-0.4-.01) A good source of calcium and trace minerals, you can use egg shells from home. Save yours from the kitchen, dry them out in the oven, then grind them into a powder. Ideal around roses, they’re also a good slug deterrent when place in a ring around the plant.

Fish emulsion (4-4-1) This liquid fertilizer is derived from fish and sometimes smells like it. It can be applied to soil as a fertilizer or used as a foliar feed.

Kelp meal (1-0-2) A source of trace minerals, iron, and potassium, kelp meal also contains plant growth hormones, so use it sparingly.

Worm castings (0.5-0.5-0.3) Worm castings are essentially worm poop. They’re a great soil conditioner and add organic matter and trace minerals to soil. Organic liquid fertilizers often incorporate worm castings.

Sources for organic fertilizer

Espoma carries an excellent line of organic supplements and plant foods. The Tone line offers organic plant foods created for specific kinds of plants.

FoxFarm’s Happy Frog line is organic. We’re also fans of Organic Big Bloom liquid fertilizer, ideal for containers.

Ask at your local garden center for additional lines that they may carry.