Two centuries ago, the earliest soil scientists discovered that ground-up bones contributed something important to fertile soil. That prompted impoverished Western farmers to gather buffalo bones from the prairies as bone meal fertilizer. Since then, it’s become commonplace to use bone meal every time flowers, particularly bulbs, are planted.

Read on to find out what bone meal is, when to apply it and how to make your own.

What Is Bone Meal?

Bone meal is the powdered skeletons of animals. It contains phosphorus, which helps plants transform the sun’s rays into blossoms via photosynthesis, as well as calcium. Both mineral elements are essential to healthy soil and plants. Bone meal also promotes root growth and benefits microbes in the soil.

You’ll find bone meal at garden centers among the fertilizers; it’s also an ingredient in all-purpose organic fertilizers. Natural bone meal releases its nutrients to plants slower than synthetic fertilizers, which usually must be reapplied during the growing season.

Do All Flowers Need Bone Meal?

No. To find out if your flowers need bone meal, determine the pH (acidity/alkalinity) of your soil. It should be balanced at pH 6 to 7.5 before applying bone meal or the phosphorus will not help your plants.

What Are the Downsides of Bone Meal?

Adding some bone meal to the soil will produce colorful blossoms and fruit, but too much can do just the opposite. Texas A&M Agrilife Extension warns excessive phosphorus may keep plants from absorbing other necessary nutrients, which can hamper plant growth. Plus, over time phosphorus can build up in the soil, eventually killing plants.

Also, phosphorus is frequently overused. When it washes into lakes and rivers, it creates a toxic environment. That’s why Michigan and 10 other states passed laws banning its application on lawns.

And bone meal can contain toxic substances like mercury and lead, making careful application and storage key. Fertilizers containing bone meal can irritate skin and airways through contact or inhaling, or cause serious illness if accidentally ingested in large amounts. It’s important to be careful around bone meal.

When to Apply Bone Meal to Flowers

Once you determine the soil pH level is balanced, apply a multipurpose fertilizer that contains bone meal close to, but not directly on, the plants. Organic, natural bone meal takes a long time to work, so don’t apply it multiple times throughout the growing season. Some fertilizers containing bone meal are meant to be applied in the fall to enhance the soil before spring planting.

How to Apply Bone Meal

When planting bulbs or potted plants, dig a hole a little deeper than necessary, put a small amount of bone meal in the hole and cover with about a quarter-inch of soil before adding the plant or bulb. University of Illinois Extension offers specific information for different types of flower bulbs and growing seasons.

For an established bed, work the bone meal into the soil around plants after determining the soil’s pH. The deeper, the better. Bone meal is taken up through roots and flows into the soil slowly, making a topical application less effective.

Note: Cornell Cooperative Extension says a cup of organic multipurpose flower fertilizer with four percent phosphorus (bone meal) is good for a five-by-10-foot flower bed.

How to Make Bone Meal

Make your own bone meal in four easy steps:

1. Collect any kind of bones. If you don’t eat meat with bones, ask for them at butcher shops or supermarkets. Store them in your freezer until you have a sufficient amount.
2. Boil off all tissues, meat and fat.
3. Bake in the oven until brittle.
4. Pulverize with a hammer.