Bone Meal Fertilizer for Plants: The Complete Guide

Blood meal, bone meal, feather meal, fish meal, kelp meal, soybean meal … The fertilizer at your local garden center is full of choices—often too many choices!  Let’s talk about bone meal, which provides phosphorus, one of the essential macro-nutrients (along with nitrogen and potassium) necessary for healthy plant growth. 

A popular organic fertilizer, bone meal has long been popular in the fall when planting spring-flowering bulbs.

It can also be an excellent amendment before seeding plants in early spring to support healthy root growth as well as enhance flowering and fruiting during the growing season.

What is Bone Meal?

Bone meal is an organic fertilizer made from dried animal bones that have been dried and ground into a fine powder. These bones are waste products from animals used for meat, so it goes back to the age-old ways of reusing and repurposing. 

Containing about 20% phosphorus, bone meal is one of the best, most readily available sources of phosphorus for your plants. It also contains about 24% calcium, many trace minerals, and a bit of nitrogen. N-P-K analyses can vary but average around 3-20-0 meaning it is low in nitrogen, high in phosphorus, and has no potassium.

Sometimes, it is sold in a raw form, but that has a strong odor and attracts animals, so now it is usually steamed before drying. This removes any fats and residue and kills any pathogens that might be lurking. Animals have strong noses, though, and even if you can’t smell it, steamed bone meal may still draw them to your garden.  

Bone meal is considered sustainable because it recycles the nutrients found in a waste product. As long as animals are being slaughtered, there will be a supply of bonemeal.

How to Use Bonemeal

Before you dump bone meal on your garden, make sure you actually need the phosphorus it contains by getting a soil test done. Also, know your soil pH before amending it. Let those results be your guide for how much to use. 

Soil is either neutral, leaning towards acidity, or leaning towards alkalinity. If your soil leads towards alkalinity, you do not need bonemeal, as it’s only available to plants in acidic soil with a pH level of 7 or lower. 

The point of bonemeal is to boost phosphorus and calcium for root growth and prevent soil deficiencies. Over-fertilizing with bone meal is not just expensive and wasteful but can actually harm your plants. The phosphorus may get tied up if soil acidity is too low or too high. Here is how do a soil test. 

Follow the directions on the bag for application rates.

When to Use Bonemeal

Spring

Bonemeal is a useful amendment when preparing the garden soil for planting. Plant uptake of phosphorus is slow in cold soil. 

• When planting early, add a thin band of bone meal 2 inches below the seed bed. 
• Give new vegetable and flower transplants a supplemental dose of phosphorus by sprinkling a pinch of bone meal in the planting hole around the root zone. 
• When planting thick-rooted perennials such as roses and peonies in their forever homes, apply bone meal mixed with soil in the planting hole to get them off to a good start. 

Summer

• Use it as a one-time side dressing for individual crops during the growing season. In places with longer growing seasons, you may use it every 8 weeks; bonemeal is an organic slow-release fertilizer. 
• Work it into the soil and water well. Since much of its phosphorus is immediately available, bone meal feeds plants for 1 to 4 months.

Fall

To promote healthy root growth in fall-planted bulbs, a small amount—under a teaspoon—is added to the hole and mixed with the soil below, where the bulbs will be placed to feed the new roots. Bulbs also appreciate the extra calcium it provides.

Benefits of Bonemeal

1. Phosphorus is a key element enabling plants to access the soil nutrients needed for early root formation and development of fruit and seeds. 
2. It also promotes the efficient use of water, aiding stress tolerance, making your plants more drought-resistant and winter-hardy. 
3. With bonemeal, plants also benefit from healthy cell growth in stalks, stems, and blossoms.

Along with stunted growth and weak stems, purple-colored leaves are an obvious sign of a lack of phosphorus. The phosphorus in bone meal aids in photosynthesis and the creation of chlorophyll, which gives plants their green color.

Alternatives

It goes without saying that many vegetarians and all vegans shun not only bone meal but all animal-based products. Thankfully, there are other sources of phosphorus for your garden. 

• Rock phosphate (0-33-0) is cheaper than bone meal and higher in phosphorus. It is a slow-release source of phosphorus, taking 5 years to break down.
• Colloidal phosphate (0-18-0) is a form of soft rock phosphate that is 18% phosphorus and 21% calcium.
• Brown phosphate has the consistency of rich soil. It analyzes at 0-3-0, but 6% of its phosphorus is readily available. It is low in heavy metals.
• Cottonseed meal (5-2-1) offers a slow-release phosphorus along with a good amount of nitrogen.
• Comfrey can supply not only phosphorus but also nitrogen, potassium, calcium, and trace minerals.

If you are not averse to using animal-based products, try these alternative sources of phosphorus.

• Fish Meal (7-13-3) contains a lot of phosphorus and nitrogen, along with many trace minerals and vitamins, but it is also smelly and expensive!
• Bat guano (3-10-1) can be used as a powder or made into a liquid foliar spray.
• Bone char (0-16-0) is simply a burned bone meal. 

Learn more about using organic soil amendments.

A word of caution: Many people sprinkle bone meal around their gardens to discourage rodents and rabbits from eating their plants. Bone meal should be incorporated into the soil rather than left on top where animals can access it, and any leftovers should be properly stored in a critter-proof container. Otherwise, you will attract wildlife. If large quantities of it are eaten, it can cause intestinal blockages that require surgery. This is rare, but it’s important to use fertilizers wisely.