One of the single most popular fertilizing amendments used around the world is bone meal. Chock full of phosphorus and calcium, bone meal has been used by farmers for hundreds of years to improve flowering and stimulate root development of their most important crops. Slow-release, easy to apply, and generally safe to use, bone meal makes it appealing for many backyard gardeners. And no doubt, you’ve seen bone meal for sale anywhere that sells fertilizer. But did you know that you can make your own bone meal right at home? And it’s actually pretty easy. Let me show you how.
What is bone meal?
As its name implies, bone meal is basically ground-up animal bones that have been cooked, boiled, or steamed, and then pulverized. Most commercial bone meals come from cow bones, but any bones will do. Bone meal is often mixed with other amendments, so nailing down a universal nutrient profile is nearly impossible. However, you can be sure that pretty much all bone meals are going to have some nitrogen and some calcium in them. At the heart of bone meal and why we use it in our gardens is phosphorus. As you’ll remember, phosphorus is the “P” in our NPK macronutrient system. As a member of the big three, phosphorus is integral to a plant’s energy system and its structure. And not only that, it’s central to photosynthesis itself. So, plants and soils low in phosphorus can definitely benefit from a bone meal amendment.
All right, now that we know what bone meal is, where it comes from, what it’s made of, and what it’s good for, let’s go ahead and make some of our own.
How to make bone meal:
Making your own bone meal is a four-step process that’s quite simple, really, only complicated by the fact that there are so many ways to do it.
The first two steps are to clean the bones of any meat or cartilage and to cook them if they aren’t already. Fortunately, these two steps are usually done simultaneously. One way you can do it is to boil the bones in a large pot for up to six hours or more. It works great for the thinner bones like chicken or turkey, but thicker cow bones simply take way too long. So, what I prefer to use instead is a pressure cooker or Instapot. Fill up the pot with all your bones and completely submerge them with tap water. Then cook on the highest setting for two or more hours. The thinner bird bones will literally fall apart in your hands while the larger cow bones will readily break apart with little effort.
Steps 3 and 4, while separate, can be done in any order. You can choose to first pulverize and then dehydrate, or you can choose to remove the moisture and then make the bone meal powder. Either method is perfectly fine; just choose the easiest one for you.
To pulverize first, you’re gonna need some sort of a blender to really grind up these cooked bones. After that, place them in a thin layer on a flat tray ready for the dehydrator. Now, to dehydrate first, simply place your bone pieces in your dehydrator set to the highest setting, space them evenly apart, and try to keep the bone fragments to around 3 inches in size or less. Both the pre-pulverized bone and the chunks are gonna take roughly the same amount of time to dehydrate, about 12 hours. Fortunately, by this stage, the smell of those bones is gone, unlike the cooking stage.
After running the dehydrator, you can really start to see these bones disintegrating on their own, turning these guys into dust shouldn’t be a problem. So, we’re almost done. The pre-crushed bone meal will still likely be a bit chunky. That’s okay. To really grind it up, simply place it into a mortar. Then, using a pestle, grind it up to that fine powder that you would expect bone meal to be like. Easy stuff. Similarly, for the larger bone pieces, a mortar and pestle should also work great to really grind them up to that powder that we’re after. You can use a blender at this point as well, but I find that it can really be murder on the blades, especially for the thicker bone pieces. But it’s up to you.
Application of bone meal is really simple. It can be added to compost, pots, containers, top-dressed right into beds and mulches, or even dug into holes as you transplant your seedlings. However, my favorite way of getting bone meal into my garden is to add it directly to my potting mixes as an amendment.
Bone meal will never burn or harm your plants at any concentration, so you can be very generous with it. But I find one tablespoon per gallon of soil to be plenty. And if you want to get really crazy and really take your amendments and potting soils to the next level, add in some seaweed fertilizer and rock dust in addition to that bone meal. Oh man, talk about supercharging your soil. Bone meal is a universally praised slow-release fertilizer that’s synonymous with healthy plants. While it’s not a complete fertilizing solution, nobody’s suggesting that. Making your own bone meal is free. It’s also easy to apply, and there’s no arguing its nutritional value. Plus, it’s one of those things that’s just fun to make.
