You may have heard that adding bone meal when planting bulbs will stimulate root growth and support big flower blooms. Unfortunately, this is a gardening myth. At best, adding bone meal does nothing for the plant and at worst can cause significant problems.
The post Add Bone Meal for Root Growth and Bigger Blooms: Busting the Garden Myth appeared first on Big Blog Of Gardening.You may have heard that adding bone meal when planting bulbs will stimulate root growth and support big flower blooms. Unfortunately, this is a gardening myth. At best, adding bone meal does nothing for the plant and at worst can cause significant problems.
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Hyacinths bloom reliably in my spring garden each year without adding bone meal.

You may have heard that adding bone meal (bonemeal) when planting bulbs each fall will stimulate root growth and support big flower blooms come spring. Unfortunately, this is a gardening myth. At best, adding bone meal does nothing for the plant and at worst can cause significant problems, depending on your soil.

If you search the topic online, you’ll find tons of results from fertilizer companies promoting their products. And blog posts from gardeners amplifying the same claims as the fertilizer companies. The claim is that phosphorous, the main ingredient in bone meal, stimulates root growth and supercharges flower blooms. But if you dig into the science, you’ll discover that in most soils, bone meal is completely unnecessary. Most garden soils in North America have sufficient amounts of phosphorous and calcium. What’s worse, an overabundance of soil phosphorous can actually harm your plants.

We should note that there are numerous studies which endorse the use of bone meal on farms. These studies typically examine specific crops with specific amounts of bone meal or meat bone meal (MBM) added to farm soil. These studies do not apply to the home garden, as gardeners grow plants under very different circumstances than farmers do. A farmer’s crops draw a higher percentage of nutrients from the soil than a patch of hyacinths, roses, radishes or peppers in a home garden. What’s good for the farm is not necessarily good for the home garden.

What is bone meal fertilizer made from?

As the name suggests, bone meal is made from crushed bones. It is an organic fertilizer with high percentages of phosphorous and calcium. Phosphorous supports root growth, flower blooms, and other plant functions and is one of the 3 primary nutrients required for plant growth, along with nitrogen and potassium (indicated as N-P-K percentages on fertilizer packaging).

In the mid-19th century, farm soils were becoming less productive. For many years, farm fields were mainly fertilized with livestock manure, which is primarily nitrogen and potassium. As the crops used up the phosphorous in the soil, not enough was replaced, making the farm soils less fertile. It was suggested by soil scientists at the time that grinding the bones of expired animals into a “meal” and then adding it to the soil would improve fertility, which it did (they actually added meat bone meal, not the same as the bone meal available today for gardeners). When synthetic phosphate fertilizer became available in the 20th century, bone meal use declined.

Why add bone meal to your garden?

We can rephrase the headline: why add fertilizer to your garden? The answer is, and always will be, to increase nutrients that are lacking in the soil. If a nutrient is not missing from the soil, then no additional fertilizer will make a lick of difference to the plant in the growing season. And fertilizers cannot “supercharge” or “stimulate” growth, they can only support it. The only way to know with certainty what is or isn’t lacking is to get your garden soil tested by a lab.

If some fertilizer is good, more is better, right? No, exceeding recommendations for fertilizers will not help plants at all. Recommendations are made based on your soil conditions and will provide nutrients in optimum ranges for plant use. Exceeding this amount will not provide benefits and can even lead to nutrient deficiencies because excesses of some nutrients can lead to poor uptake of others. Additionally, excess nutrients can be lost to the environment and degrade streams and rivers.

Getting The Most Out Of Your Home Vegetable Garden Soil Test Report, Natalie Bumgarner, Assistant Professor and University of Tennessee Extension Specialist, Department of Plant Sciences.(pdf download)

Buy on Amazon: Soil Test Kit.

How bone meal can harm plants.

Soluble phosphorous – the only form plants use – takes years to form as soil microbes break down fertilizers and organic matter. Plants on their own have difficulty taking up soluble phosphorous in the soil. To get what they need, they form symbiotic relationships with mycorrhizal fungi, which you can read more about here. These fungi attach to a plant’s roots and are very efficient at extracting phosphorous from the soil. The fungi send the soluble phosphorous to the plant through the roots, in exchange for sugars from the plant.

So in most soils in North America with a neutral or alkaline pH, when you add bone meal at planting time around that tulip bulb, it won’t help the tulip very much. The newly added phosphorous remains unavailable to the plant for years. However, if you have acidic soil (low pH) and low phosphorous, the phosphorous in bone meal becomes quickly soluble and is easily available to the plant (chemistry at work!). As the plant no longer needs the mycorrhizal fungi relationship, it stops connecting with them and the fungi die without the plant sugars. But without the fungi, the plant has to devote extra resources to root growth at the expense of other plant functions.

When plant roots are in low phosphorus environments, they exude organic acids from their root tips. These acids allow mycorrhizal fungi to penetrate the roots and form the networks that assist plant roots in taking up water and nutrients. Mycorrhizae are particularly adept at extracting phosphorus from the soil.If phosphorus levels are too high, however, the roots do not exude the organic acids and mycorrhizal connections do not form. This forces the plant to put more resources into root growth to compensate for the lack of mycorrhizae. So in a sense, phosphorus will increase root growth – but at an added cost to the plant. The resources expended by the plant in growing additional roots to take the place of mycorrhizae are not available for other plant needs.

The Myth of Beneficial Bone Meal, Linda Chalker-Scott, Ph.D., Extension Horticulturist and Associate Professor, Puyallup Research and Extension Center, Washington State University. (pdf download)

Adding bone meal will not grow bigger roots and bigger blooms.

All of the elements in fertilizer work in balance in plants – too little or too much of one nutrient affects every plant function. Therefore, your plants can’t grow bigger roots and blooms unless you also have sufficient quantities of nitrogen and potassium to support top growth and other functions. And if there’s more phosphorous in the soil than the plant needs, the plant simply won’t use it. Additionally, phosphorous is rarely leached from the soil by weather and barely moves through it. So if there’s enough phosphorous in your garden soil today, there will probably be enough years from now.

Resources: Some Garden Myths and What Research Has to Say, Oregon State University Extension Service; Is Bone Meal Good For The Garden?, Garden Myths; Should I Use Bone Meal When Planting My Spring Flowering Bulbs?, University Of New Hampshire; Fertilizing Flower Gardens and Avoid Too Much Phosphorus, University of Massachusetts Amherst; Bonemeal, Wikipedia.

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