Blood meal is a dry, powdered fertilizer made from animal blood, typically collected from cattle or hogs during meat processing. With a nutrient ratio of 12-0-0, it delivers 12 percent nitrogen and nothing else, making it one of the most concentrated organic nitrogen sources available to gardeners. It’s used primarily to fuel leafy growth, correct nitrogen-deficient soil, and repel certain garden pests.
How Blood Meal Is Made
Blood meal starts as liquid blood collected at slaughterhouses and rendering plants. The manufacturing process reduces its moisture content from roughly 88 percent down to under 10 percent through three main stages: coagulation, decanting, and drying. First, steam is injected into the liquid blood (about 150 kilograms of steam per ton of blood), which causes the blood to solidify. A centrifuge then separates the solids from the liquid, dropping moisture to around 68 percent. Finally, a flash dryer blasts hot air through the material, pulling the remaining water out quickly and producing the fine, dark powder sold in bags at garden centers.
The result is a shelf-stable product that’s easy to store and spread. Most commercial blood meal comes from bovine or porcine sources, though the label doesn’t always specify.
Why Gardeners Use It
Nitrogen is the nutrient most responsible for green, leafy growth. Blood meal delivers it in a form that soil microbes can break down relatively quickly, releasing nitrogen over a period of several weeks to a few months depending on soil temperature and moisture. That makes it especially useful for heavy-feeding crops like corn, broccoli, spinach, and other leafy greens that pull large amounts of nitrogen from the soil throughout their growing season.
Blood meal also lowers soil pH slightly as it decomposes, which benefits acid-loving plants like blueberries, azaleas, and rhododendrons. If a soil test shows your pH is already low, this is worth keeping in mind before applying.
The strong smell of blood meal serves a secondary purpose: it repels deer, rabbits, squirrels, raccoons, and moles. The scent mimics a predator presence, discouraging animals from browsing in treated areas. The effect fades as the blood meal breaks down, so reapplication after rain or every few weeks helps maintain the deterrent.
How to Apply Blood Meal
Because blood meal is so nitrogen-dense, a little goes a long way. A general starting point for garden beds is roughly 1 to 2 pounds per 100 square feet, mixed into the top few inches of soil. For individual plants, a tablespoon or two worked into the soil around the base is typically sufficient. The key is to avoid dumping it in concentrated piles. Spread it evenly, scratch it into the surface, and water the area to help it begin breaking down.
You can apply blood meal at planting time and again midseason if your plants show signs of nitrogen hunger, like yellowing lower leaves or slow, stunted growth. A soil test beforehand removes the guesswork and tells you whether nitrogen is actually what your soil needs.
Risks of Using Too Much
The most common problem with blood meal is nitrogen burn. Because it’s such a concentrated source, it’s easy to create a nitrogen spike that plants can’t absorb fast enough. The classic symptom is leaf tip burn, where the tips of leaves turn brown and crispy and the edges curl inward. Plants may also become unusually dark green with soft, watery stems that bend easily and attract pests.
Excess nitrogen can also interfere with a plant’s ability to take up other nutrients like potassium, calcium, and magnesium. When that happens, you may see odd leaf symptoms that don’t look like a nitrogen problem at all, because the real issue is a nutrient imbalance rather than a deficiency. One tricky scenario occurs when blood meal is applied during cool or dry conditions, when microbial activity is slow. The nitrogen sits in the soil unused, then once temperatures rise or moisture returns, everything releases at once and plants suddenly look burned or overly lush.
The fix for over-application is heavy watering to flush excess nitrogen below the root zone, and then waiting. There’s no quick way to remove nitrogen that’s already in the soil.
Blood Meal vs. Bone Meal
These two are often sold side by side and sometimes confused, but they do very different things. Blood meal is a nitrogen fertilizer (12-0-0), promoting leafy, vegetative growth. Bone meal is a phosphorus source, typically around 3-15-0, which supports root development and flowering. Blood meal feeds the tops of your plants; bone meal feeds the roots and blooms.
They can be used together when a soil test shows deficiencies in both nitrogen and phosphorus. Mixing them doesn’t create any harmful interaction. But applying either one without knowing what your soil actually lacks is a common way to waste money or create nutrient imbalances.
Blood Meal as Animal Feed
Beyond the garden, blood meal is widely used as a protein supplement in livestock and aquaculture feed. Its crude protein content is exceptionally high, averaging around 94 percent on a dry-matter basis, making it one of the most protein-dense feed ingredients available. It’s used in poultry, swine, and fish diets to boost overall protein intake.
In the United States, the FDA regulates which animal-derived proteins can be fed to which species. Blood and blood products are specifically exempt from the rules that prohibit feeding mammalian proteins to ruminant animals (cattle, sheep, goats). Those rules exist to prevent the spread of BSE, commonly known as mad cow disease. The exemption for blood meal reflects that blood is considered a lower-risk tissue compared to brain or spinal cord material, which are the primary carriers of BSE.