You’ve probably heard of bone meal for plants but how does bone meal affect orchids? At first, I was skeptical, thinking bone meal was a Halloween trick or some haunted ghost story. It’s not something I’d naturally think of—adding bones to plants.
What exactly is bone meal and how does it affect orchid care?
Bone meal raises the pH of your orchid potting media, while it neutralizes high levels of iron, nitrogen, and mercury. Being high in calcium and phosphorus, bone meal helps your orchid blooms last longer. The downside of bone meal is that it can attract more problems than add benefits.
What is Bone Meal Made of?
Bone meal is made from animal bones (hopefully animal) that have been either boiled or steamed to separate the fat and muscle from the bone.
The boiling also kills any bacteria and diseases that may linger around from the carcass. Without boiling, the nutrients aren’t dissolved, therefore, they can’t be absorbed by the orchid.
Once the bones have been boiled, they are pulverized into a fine powder that can be sprinkled on top of your orchids or flower beds.
I honestly had no idea that this was a true “thing” and I keep wondering to myself who was the first person who tried this? Did they have leftover bones just lying around?
I tried to find this answer (curiosity got to me) and the method was first suggested by slaughterhouses. They discovered that adding the pulverized bone meal into the soil made the flowers and nearby crops healthier.
NKP in Bone Meal
The nutrients that resulted from this powder were calcium and phosphorous. That was the surprising discovery about bone meal. Calcium was to be expected because our bones are made strictly from calcium, but phosphorous?
I searched for various companies that sold bone meal and the NPK values of their products. They all said it was strictly bone meal in the bags, but the numbers still varied. My guess is that depended on the type of animal and the process it went through to grind the bones, but the NPK ratios were:
That translates into a sustainable amount of nitrogen (3, 4, 2) and a very high amount of phosphorous (15, 12, 22). No potassium was found in any examples that I looked for.
If you are wondering what NPK is, I suggest this article where I explain each of those. But don’t forget to come back here and finish reading this article. 😊
How Much Bone Meal To Apply to Orchids
Bone Meal products are sold mainly to farms and crop plantations. Smaller bags can be found for outdoor lawns and gardens, but nothing was small enough for orchid pots (unless you have thousands of orchids).
To me, the measurements were a bit hard to interpret: you need to use 10 lbs (4.5 kg) of bone meal to spread over 100 square feet (9 square meters) of land.
My orchid pots are a maximum of 6 inches each. From my limited math, that means if I use the size of a quarter and mix it in with the potting media each time I repot, I’ll be okay.
There are 2 ways to apply bone meal to your orchid pots: 1) by adding bone meal to the top of the orchid pot, sprinkling it around the top layer of potting media, or 2) by mixing it in with the potting media at the time of repot, spreading it evenly throughout all layers of the pot.
The initial use of bone meal in soil was that the farmers (and flower gardeners) would dig up the top layer of soil, bury the bone meal, and add a top covering of soil.
This would enhance the soil nutrients quicker since the bone meal would interact quicker with the soil around it. The roots would grow down into the nutrient-rich soil and have access to calcium and phosphorus. (Source)
Which method was better for orchids? I still don’t know. I’m testing it out and seeing which orchid reacts better to it. So far, tiny benefits have been visible in both pots. I’ll keep you updated on how it goes later.
What to Expect from Orchids After Bone Meal Is Applied
At first, don’t expect visible results. This is because bone meal will react slowly to its outside conditions. That is one of the cons of using bone meal. It’s considered a slow-release fertilizer, so don’t expect to see anything visible for at least four to six months.
Once the bone meal starts to degrade into a form that the orchid roots can absorb it, you should expect the leaves to be greener and sturdier. The blooms will stay open longer due to the more nutrients it has to keep the blossoms open.
This happens for various reasons. Firstly, bone meal balances out the high nitrogen in the potting media. Sometimes the media is so saturated with fertilizers since nitrogen appears in all of them. Too much nitrogen can be harmful to your orchid, causing other nutrients to not be absorbed. (Source)
Bone meal also balances out the mercury and lead that can be too high in your orchid pot. Inorganic mercury can be found in tap water. Even though it is safe for human consumption, it is not for orchids.
Lead isn’t added to the tap water at its initial source, but the lead from the pipes, faucets, and plumbing fixtures can raise those levels. It’s best if you use distilled water or another form of water. If you’re not sure what kind of water to use, this article I wrote might help (link).
Another consequence of bone meal is that the soil will raise a few points in pH. If your potting media is frequently lowering, going to acidic, then bone meal can be a great addition to raise that acidic level. It won’t jump from 3 to 8, but it will raise the pH from 5.0 to 5.5 in a period of four months.
If you don’t want to use bone meal, you can use dolomite lime to do the same thing. I wrote an article about dolomitic lime that you can read here (link). At least for me, I’m more comfortable using that than bone meal. It’s a psychological thing…
One important thing you need to know is that bone meal will not be absorbed by any soil or potting media if the pH is above 7. The pH becomes more alkaline than the bone meal can stand, and it isn’t absorbed by the plants. (Source)
This is very important when using bone meal in orchid pots because if you have an orchid that prefers more alkaline environments (usually lithophytes—orchids attach to rocks and cliffs) and your media is above 7, then scratch bone meal from your list.
It won’t work.
What Orchid Genera Can Benefit from Bone Meal
When you think back to the garden use of bone meal, the soil played a big part in the breaking down of the bone meal. This means that the soil’s microbes are necessary (but not essential) in how well this product works.
By adding bone meal to terrestrial orchid media, they will raise the pH (which most terrestrial orchids prefer anyway) all while providing important sources of calcium and phosphorous. It’s a fine line though, because raising the pH above 7 will inactivate the bone meal.
Cypripediums (all lady slipper orchids for that matter) and Calanthe are among the most common. Cymbidiums can also benefit from bone meal. You can read an article about Lady Slippers and their categories here (link).
Cons of Bone Meal for Orchids
After reading the wonderful benefits of bone meal, I just want to say why I don’t use it… I still have my orchids under observation, but even if they do produce a good, positive reaction to bone meal, I’d prefer to stay away from its use.
1) Bone Meals attracts Dogs and Raccoons
Just as using bone meal to enhance growth for your orchids that prefer to be outside, bone meal can attract a list of several negative effects. The first—dogs.
If you have a dog, avoid using bone meal. They will dig up everything in your lawn and overturn your pots after that “doggone-good” smell of bones. It’s not their fault… After all, they have a great sense of smell.
If you don’t have outdoor dogs and live near wooded areas, beware of raccoons. They are the 2nd runner up in digging up bone meal.
2) Bone Meal Attracts Fungus Gnats
Let’s say you grow your orchids indoors like I do. This means that the orchid with bone meal will still attract critters, but on a smaller scale—fungus gnats. These pesky little dudes are almost near impossible to get rid of, but I found a few suggestions, which you can read about in this article (link).
3) Bone Meal takes a Long Time to Decompose
Another con of using bone meal in orchids is that it is slow release—as in really sloooow release. Since we repot every 2 years, the effects of it in your orchid pot won’t be very showy.
If you use it for lawn purposes, then that’s different.
4) EXACT NPK OF BONE MEAL IS UNKNOWN OR VARIES
Another reason to not use bone meal as an orchid fertilizer supplement is that the exact NPK and other elements ratios is not exactly clear. You have no idea what the exact concentrations are. Too much can cause plant toxicity and too little can cause nutrient deficiency.
5) Bone Meal Breaks Down the Orchid Potting Media
Bone meal has another disadvantage. If you are using sphagnum moss and orchid bark, bone meal will break down and decompose those faster than your pots will arrive from Amazon. Bone meal is a bit aggressive on organic potting media.
If your potting media is not organic, and you have lava rock, perlite, pebbles, or any other inorganic material, then I’d say that bone meal is safe to use.
Conclusion about Bone Meal for Orchids
In all, bone meal is a subject I don’t have a strong opinion about. As I said before, there are several benefits in using bone meal for orchid care, but I really don’t know if they are that superior to the cons.
Even if in the long run my experiment orchid with bone meal does provide healthier results, I just can’t get over the fact that this is an animal I’m spreading over my plants. It’s my elephant in the room.
I doubt I’ll be using bone meal for my orchids again, but if you want to purchase some and test it on your plants, here’s the link to the one I bought (Affiliate Link).
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In all, I hope this article clarified a few things about bone meal. If you have any questions or if there is something I forgot to mention, please comment below.