We’ve got a bone to pick with phosphorus – there aren’t a lot of natural & organic options out there. But bone meal is an awesome one. It is made of steamed animal bones (ours comes from pork bones) that are ground into a meal texture, and is high in both phosphorus and calcium. Bone meal is considered a slow-release phosphorus source, but compared to rock phosphate, it’s super speedy. Rock phosphate has to weather over several months, even years, while bone meal breaks down completely in four months or less. The phosphorus from bone meal is also more bioavailable, increasing the uptake by plants.

Phosphorus is not very mobile in soil because it bonds so tightly to soil molecules. So one of the secrets of getting the most out of your bone meal is to simply prevent erosion that carries phosphorus-rich soil particles away. But that immobility also means that for bulbs and tubers, it is important to mix bone meal into the soil where it is needed, and not just in the top couple inches of soil. Be sure to incorporate bone meal throughout the planting hole for flower bulbs and potatoes or other tubers.

Another key to using bone meal or any other phosphorus source is to test your soil’s pH. When pH gets more alkaline, above 7, phosphorus from any source becomes less available to plants. Managing your soil pH before fertilizing will also help improve your plants’ phosphorus uptake from bone meal.

You’ll find bone meal in most of our signature blends, because of phosphorus’s important role in plant reproduction, especially for flowering or fruiting plants. It is especially beneficial for bulbs, tubers, root crops, shrubs and fruit trees. Our NaturalPhos™ bone meal is also OMRI certified for use in organic farming.