When planting roses one of the most common instructions is always to “toss a cup of bone meal in the bottom of the hole”. The reasoning behind this is that bone meal is phosphate, roses really need it and since it doesn’t travel through the soil quickly it’s best to put it in the hole.
I used to do this very early in my rose days, but then stopped doing so when I started the nursery. I did a soil analysis and the results didn’t call for it. I’ve not done it since and quite frankly never noticed any difference. So I never thought about it again, and when people asked me if they should use it I simply replied by saying you can if you want to but I don’t.
I figured after all, what harm can it do?
At least that is what I thought until someone posted a link on our Discussion Forum to a short paper by Linda Chalker-Scott, Ph.D., Extension Horticulturist and Associate Professor, Puyallup Research and Extension Center, Washington State University. She entitled the paper
“The Myth of Phosphate, Part II. Roses need phosphate fertilizer for root and flower growth”
She began by noting that she could not find any scientific research saying that roses needed more phosphate than other plants. And in fact the phosphate levels of most soils are perfectly adequate for roses and all plants – something my soil analysis and observations noted all those years ago.
But then the next part really made me stand up and take notice. I quote.
“Numerous studies have demonstrated that roses, like most terrestrial plants, maintain symbiotic relationships with beneficial fungi. If you add phosphate to your rose plants, you will decrease the ability of mycorrhizal fungi to colonize the rose roots.”
That was an eye opener. I’ve always preached against those systemic all in one fertilizers, fungicides and insecticides because studies show the have an impact on vital soil life but this was new. Professor Chalker goes on to add.
“Without these fungal partners, rose roots must work harder to extract water and nutrients from the soil. Moreover, this excess phosphate is injurious to other soil organisms. With increased fertilizer additions, soil salinity increases. You have now created an artificial system in which soil health is so impacted that you must continue to add fertilizer for your plants to survive.”
Now that last statement is great news if you own stock in a chemical fertilizer company but not good news for your roses. Those living soil organisms supply the natural nutrients that work in harmony with your roses to boost their own natural immune system. Professor Chalker is suggesting that by adding artificial fertilizers we are actually getting in the way of that process.
Professor Chalker-Scott goes on to say this.
“I believe this is what has happened in many landscapes that feature roses. Well-intentioned, yet misguided, homeowners over apply phosphate and other fertilizers, insecticides, and fungicides until the soil system is so impacted that it becomes non-functional. Without the beneficial soil organisms, roses become more susceptible to nutrient deficiencies and opportunistic diseases, causing rose aficionados to add even more of these chemicals.”
One more reason to just treat roses like any other plant. After all Roses Are Plants, Too.
If you wish to read the paper click here for a link.
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