Blood meal is a natural, organic fertilizer derived from dried animal blood, typically a by-product of the meat processing industry. It is processed into a fine, dark powder or granular form. It is primarily used to address nitrogen deficiencies in the soil and promote vigorous vegetative growth in plants, supporting the development of lush, green foliage.
Blood Meal’s Role in Plant Development
The primary function of blood meal stems from its remarkably high nitrogen content, often carrying an NPK ratio around 12-0-0 or 13-0-0. This composition means it is packed with nitrogen but contains virtually no phosphorus or potassium. Nitrogen is a fundamental component of chlorophyll, the pigment responsible for capturing light energy during photosynthesis.
A healthy supply of nitrogen promotes the rapid production of proteins and enzymes within the plant, supporting fast growth and the development of strong, thick stems. When applied to the soil, microbes convert the organic nitrogen into plant-available forms. This conversion process makes it a relatively fast-acting organic fertilizer compared to other natural amendments. The quick availability of nitrogen helps correct deficiencies, which often manifest as yellowing or pale green leaves.
Heavy Feeders and Leafy Greens
Blood meal is particularly beneficial for plants that require a substantial and constant supply of nitrogen to fuel their rapid growth, often called “heavy feeders.” This category includes many annual vegetables grown for their substantial leaf production or quick maturity. Specific examples include the brassica family, such as cabbage, broccoli, and kale.
Leafy greens like spinach, lettuce, and collard greens thrive on the nitrogen boost, supporting the lush, vibrant leaf growth gardeners desire. Corn is another well-known heavy feeder that benefits significantly, especially during its early vegetative stages when establishing a large stalk. Applying blood meal early provides the necessary fuel for maximum vegetative development before plants shift energy toward flowering or fruiting.
Application Techniques and Safety
Due to its concentrated nature, blood meal must be applied carefully to prevent damage to plants. For dry application, it should be mixed thoroughly into the top few inches of soil before planting or lightly side-dressed around existing plants. A common application rate is about one cup for every twenty square feet of garden space, or approximately one teaspoon worked into the soil around the base of a single plant.
For a liquid feed, the meal can be diluted with water, but gardeners should always follow the specific instructions on the product label for the correct ratio. Immediately after application, it is recommended to water the area thoroughly to help distribute the nutrients and prevent root burn. Reapplication should typically occur every four to six weeks during the peak growing season to maintain nutrient levels.
The most significant safety consideration is the risk of “nitrogen burn,” where excessive nitrogen concentration damages plant roots and foliage. Applying too much blood meal or letting it sit in clumps can create a toxic environment for roots, leading to browning or wilting. The strong scent of blood meal can also act as a mild deterrent, discouraging common garden pests like deer, rabbits, and voles when lightly sprinkled around vulnerable plants.
When Blood Meal Should Not Be Used
While nitrogen is necessary for all plant life, a high dose from blood meal is inappropriate for several types of plants and specific stages of growth. Root vegetables, such as carrots, potatoes, radishes, and beets, are negatively affected by excess nitrogen. The fertilizer encourages abundant leaf growth above ground at the expense of the edible root or tuber below, resulting in small harvests.
Legumes, including beans and peas, generally do not require supplemental nitrogen because they have a symbiotic relationship with soil bacteria that fix atmospheric nitrogen directly into the soil. Adding blood meal can reduce their natural nitrogen-fixing activity, making it an unnecessary application. Furthermore, for flowering and fruiting plants like tomatoes, peppers, and squash, using blood meal past the early vegetative stage is discouraged. High nitrogen levels can delay or inhibit flowering and fruiting, causing the plant to remain in a leafy growth phase and reducing the final yield.