Blood Meal: What It Is and When to Use It

closeup of blood meal texture

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"Blood meal" may not sound like something you would want in your garden, but it is actually a very useful gardening product. It is widely available at major garden centers and home improvement stores. Most gardeners use it as a fertilizer, but it can also be used to deter pests like squirrels and rabbits. On the other hand, it can attract other critters that you may not want visiting your vegetable patch.

What Is Blood Meal?

The "blood" in blood meal refers to the blood that is a by-product of the slaughtering that occurs at meat packing plants. It is most often cow blood but can be the blood of any animal slaughtered for its meat. The blood is dried into a powder before being packaged for sale as blood meal.

The origin of the "meal" in blood meal may be less apparent to most people, because it refers to a seldom-used definition of "meal": a course, unsifted powder ground from edible seeds of any grain (like cornmeal, for example). Except in blood meal, it is dried blood that is ground into a powder, not grain.

Benefits of Blood Meal

In its capacity as a fertilizer, the chief benefit of blood meal lies in its high nitrogen content. If you look at the NPK sequence on the blood meal's package, it will indicate either nitrogen and nothing else, or predominantly nitrogen with just a bit of phosphorous and potassium. This maked blood meal iparticularly good at providing a boost for plants suffering from nitrogen deficiency.

In its capacity as a pest deterrent, the chief benefit of blood meal comes from its smell, which some animals find repellent. For example, it will repel deer, rabbits, and moles. If you find your garden vegetables are being nibbled on, sprinkle blood meal lightly across the leaves and at the base of the plant.

Blood meal has other benefits, too:

  • If you want to experiment on a small scale with blood meal for amending the soil or for deterring pests, it is easy to do so, because it commonly comes in small, inexpensive packages. A 3-lb. bag costs less than $10.
  • Blood meal is organic (in the sense that it is not a chemical fertilizer).
  • It will acidify your soil, which is great if you have acid-loving plants.
  • It is a slow-release fertilizer (1 to 4 months).

Disadvantages of Using Blood Meal

Just because it is "organic," that does not mean that you can apply as much blood meal as you want around plants without thereby inviting unintended consequences. Blood meal is a concentrated form of nitrogen and excessive use can lead to other problems. Though nitrogen is great for fostering the foliage on a plant, too much of it can impede flowering. Excessive nitrogen is sometimes the culprit when plants are not producing as many flowers as you would like. Excessive amounts of nitrogen can even burn plants or, worse yet, kill them. To avoid such problems, follow the application instructions on the package of blood meal.

Blood meal has other disadvantages, too. For large gardens, it would get expensive to buy multiple small packages of blood meal from a home improvement center. In this case, it would be better to buy in bulk. A 25-lb bag costs around $32.

Additionally, not all plants like the kind of acidic soil that results from using blood meal. The distinct odor can also attract carnivores, like neighborhood dogs, to your garden.

When to Use Blood Meal

Apply blood meal in spring as soon as you see plant growth. Re-apply every 2 to 3 months thereafter until the growing season is over. Use 1 to 2 lbs. per 100 square feet. A 2-lb. application is considered a heavy feeding; until you become familiar with this product, apply just 1 lb. per 100 square feet. You can also use blood meal as a side-dress; but, again, err on the side of using less rather than more, since measurements for side-dressing are not precise.

Because using blood meal is not without its risks, it is best to use it as a fertilizer only when needed. Yellow leaves are often an indicator of nitrogen deficiency. These weak leaves cannot take up nutrients through photosynthesis which makes an application of blood meal a good solution for restoring the plant to health.

Alternatives to Blood Meal

There are other by-products from animal processing that are used as fertilizers, including:

  • Fish fertilizers: These are made from whatever is left over at fish processing plants, including bones, scales, and skin. They are high in nitrogen, phosphorus, and potassium.
  • Feather meal: This is composed of the ground-up feathers of birds at poultry processing plants. It is similar to blood meal in the sense that it provides almost exclusively nitrogen.

Bone Meal vs. Blood Meal

Blood meal and bone meal (a product composed of animal bones collected from slaughterhouses that are steamed and ground up) sound a lot alike, and they do have some similarities. Blood meal and bone meal both come from animals; are used as an organic, slow-release fertilizer; and are sold in a form that looks powdery. They both can burn plants when used in excess and can attract dogs.

However, their differences are what will affect your decision of which to buy.

Blood Meal
  • Supplies plants with nitrogen

  • Promotes healthy foliage growth

  • Applied to spring-flowering bulbs once you see growth in spring

Bone Meal
  • Supplies plants with calcium and phosphorus

  • Promotes flowering and healthy root development

  • Applied to spring-flowering bulbs when planted in the fall