Art Drysdale - April 2001

Spring is coming, bone meal advocates will be out in full force--but don’t be fooled!

"Although I have heard and read otherwise, azaleas and rhododendrons are one of the types of plants (Ericaceous) for which bone meal is not a good idea due to their liking of acid soil. For decades I've advised against bone meal for any type of plant and want to outline again why!"

My first job when I graduated from The Niagara Parks Commission Botanical Garden and School of Horticulture, was with the Shur-Gain Division of Canada Packers, where I was in charge of, among other things, writing directions for use of new consumer fertilizer products, formulating and conducting tests on experimental products (such as the first weed and feed product in Canada), and generally informing the trade and the public of advances in plant nutrition. I had just come from a school where we were taught in great detail about fertilizers--particularly those that were “natural”. I well recall the late ‘Bert’ Henning, our endeared school superintendent, preaching the use of some of the oddest concoctions as plant foods. These included seaweed (still available) cottonseed mash, and of course blood meal and bone meal.

So I arrived in Toronto’s packinghouse district with all this knowledge, only to find that the country’s leading producer of bone meal--Swift Canadian--itself admitted that virtually all of the bone meal from all of the packinghouses was even then (1961) going into the production of the much higher-priced feeding bone meal. (Some time earlier the major packinghouses had agreed that on certain not-large-volume-not-very-profitable products, one packinghouse in an area would process the entire amount of that product, and Swift Canadian was the designated processor of bone meal.)

An additional problem was that any bone left over from feeding bone meal production (basically the very poor quality bone; all the best quality went for the feeding bone meal) was being subjected to greatly increased steaming techniques to extract gelatine and other saleable by-products. In a sentence, the bone meal being offered for sale, even 40 years ago, was definitely inferior to using the ever-so-much cheaper super phosphate 0-20-0 for the application of phosphorus to encourage root growth as well as flower and seed production.

For almost two decades from that point on I had been preaching the exclusion of bone meal from gardens, not just because it was overly expensive, but also because it in some cases, could be a negative in garden soils.

Then an old friend came to the rescue--Dr. R. Milton Carleton, horticultural scientist with the Vaughan Seed Company in Chicago (see info on “Milt” in my September, 2000 Commentary), wrote a piece in News and Views, published by the American Horticultural Society. It was reprinted in the prestigious Brooklyn Botanic Garden Record, Vol. 37 No. 4, published in the winter of 1981-82. In his piece Milt reiterated much of what I had been telling my audiences through the 60s and 70s, as garnered first-hand from my involvement with the packinghouse industry in this country. Here are excerpts from Milt’s item, still valuable comments today.

“Question the value of bone meal as a fertilizer and someone is certain to rise and say, ‘If you’re so smart, why is it that our grandfathers have used bone meal for years and have been satisfied with the results?’

“The accusation has a very simple answer. Comparing the bone meal of grandfather’s day and the commercial product sold today is like comparing a dish of old-fashioned oatmeal with a serving of devitalized, dehydrated corn flakes. They are not identical.

“In the potting shed on big estates in England, or perhaps the hen house on humbler properties, there stood a bone grinding mill operated by a huge wheel. It was used to crush bones from the kitchen and was used either as a poultry feed or a garden fertilizer. Into this mill went fresh bone, perhaps from a rare roast with bits of meat still clinging to it. The marrow contained blood and also some phosphorus still in transit in the animal when slaughtered and not deposited as insoluble tricalcium phosphate, the basic building block of skeletal matter. The ground bone contained as much as six percent nitrogen.

“How does this compare with the dry, white bone meal of commerce? Today, bones are a valuable source of packinghouse by-products; elements needed by plants but worth far more in other forms. The bones are steamed to extract gelatine and other by-products. This removes most of the amino acids, a valuable source of nitrogen. Further processing removes all but about one-half percent of the nitrogen. What is left is a substance considerably less desirable as fertilizer material.

“Recently I had an occasion to examine a lawn on which the owner had faithfully applied fifty pounds of bone meal every spring for 20 years. It was pale in colour and growing poorly. A divot removed from the turf showed a distinct white line, nearly half an inch deep, just below the surface. Among other adverse effects, this layer of bone meal had locked up practically every trace of iron, robbing the grass plants of a basic nutrient needed for chlorophyll formation. It is obvious that today’s bone meal is not what it used to be. In fact, it may sometimes do more harm than good when added to the soil.”

One final comment about blood meal: I also remember the guys at Canada Packers working in blood meal processing at the plant. They could only work in ten-minute shifts or they would pass out from the strong stench. Now, blood meal has been considerably deodorized and it is still the best fertilizer for the likes of arborvitae and cedars. But do keep in mind it can create a smell not all that desirable!