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#16
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Hydrangea colours
In article , Jason Pope
writes Victoria Clare wrote: I piled it all in a heap under the hydrangea, meaning to do something about it later. This produced a strange effect: the side of the hydrangea next to the little pile of rusty things is now a vibrant blue, but scales through purple to pink on the other side! I've now distributed the items more evenly around the plant, and hope it will all be blue soon. They are hidden under a layer of mulch. Victoria The rust from the nails alters the soil pH which causes the effect you mention, it is grounded in good science! Can you elaborate on that? I thought rust was iron oxide, which I thought was alkaline, but hydrangeas go pink, not blue, in alkaline soils. Are you sure it's a change of pH that's having the effect, rather than greater availability of iron? -- Kay Easton Edward's earthworm page: http://www.scarboro.demon.co.uk/edward/index.htm |
#17
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Hydrangea colours
Kay Easton wrote:
In article , Jason Pope writes Victoria Clare wrote: I piled it all in a heap under the hydrangea, meaning to do something about it later. This produced a strange effect: the side of the hydrangea next to the little pile of rusty things is now a vibrant blue, but scales through purple to pink on the other side! I've now distributed the items more evenly around the plant, and hope it will all be blue soon. They are hidden under a layer of mulch. Victoria The rust from the nails alters the soil pH which causes the effect you mention, it is grounded in good science! Can you elaborate on that? I thought rust was iron oxide, which I thought was alkaline, but hydrangeas go pink, not blue, in alkaline soils. Are you sure it's a change of pH that's having the effect, rather than greater availability of iron? From a website: http://www.nobleplants.com/articles/...20culture.html Blue or pink colors are predicated on the amount of aluminum in the soil solution that can be absorbed by the roots. Although pH is often listed as the agent of color change, it is actually an instigator of (a precursor to) the process. If soils are acid, aluminum is available; if more alkaline then aluminum is tied up in insoluble forms and not readily available for uptake. So the true story is that high acidity, i.e. low pH, solubilizes (or makes available) aluminum; the reverse at low acidity (high alkalinity), high pH. Excess phosphorous in the soil will also tie up the aluminum in insoluble precipitates, even in acid soils. Hydrangea macrophylla grown in pine bark medium, pH 5 to 6, are typically pink. Why? The acidity is high, but almost no aluminum is present in the substrate (bark). Soil is composed of minerals, typically aluminum, silicon, iron, etc., and therein resides the difference. So how do growers produce blue hydrangeas in pine bark? Aluminum sulfate is added to the surface of the container at a prescribed rate, usually 0.75 to 1.5 ounces evenly distributed on the surface of the 3-gallon container medium. Greenhouse growers also apply it as a drench at the rate of 2.4 ounces per gallon solution with 8 ounces applied as a drench per 6 inch container. Greenhouse treatments start at budbreak and continue every 2 weeks for 3 additional applications. Growers have variable timetables for application but in our work as soon as flower buds are visible, a single application is made. Water thoroughly after application to insure solubilization of the aluminum and movement into the root zone. Too much is worse than too little and I have dwarfed and killed plants with excessive applications. The crux of the color change is that aluminum ions complex with the pigment, delphinidin-3-monoglucoside, in the sepals to produce the blue coloration. A positive correlation between intensity of blue and aluminum foliar concentration has been demonstrated. Growers try to develop antique shades, somewhere between the rich blues and pinks by combining lime in the medium and aluminum applications (see photos below). From my experiences, any pink-sepaled form, perhaps not ‘Preziosa’, can be blued and vice-versa. Although various cultivars are often listed as pink or blue, I don’t totally believe it. Lacecaps and mopheads respond in a similar fashion. The white cultivars typically are not affected and maintain their color. |
#18
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Hydrangea colours
In article , Jason Pope
writes Kay Easton wrote: In article , Jason Pope writes Victoria Clare wrote: I piled it all in a heap under the hydrangea, meaning to do something about it later. This produced a strange effect: the side of the hydrangea next to the little pile of rusty things is now a vibrant blue, but scales through purple to pink on the other side! I've now distributed the items more evenly around the plant, and hope it will all be blue soon. They are hidden under a layer of mulch. Victoria The rust from the nails alters the soil pH which causes the effect you mention, it is grounded in good science! Can you elaborate on that? I thought rust was iron oxide, which I thought was alkaline, but hydrangeas go pink, not blue, in alkaline soils. Are you sure it's a change of pH that's having the effect, rather than greater availability of iron? From a website: http://www.nobleplants.com/articles/...ory%20&%20cult ure/care%20&%20culture.html snip explanation of availability of aluminium depending on pH OK - that's fair enough ... but where does the iron come in? Or did I miss something? -- Kay Easton Edward's earthworm page: http://www.scarboro.demon.co.uk/edward/index.htm |
#19
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Hydrangea colours
"Kay Easton" wrote in message ... In article , Jason Pope writes Kay Easton wrote: In article , Jason Pope writes Victoria Clare wrote: I piled it all in a heap under the hydrangea, meaning to do something about it later. This produced a strange effect: the side of the hydrangea next to the little pile of rusty things is now a vibrant blue, but scales through purple to pink on the other side! I've now distributed the items more evenly around the plant, and hope it will all be blue soon. They are hidden under a layer of mulch. Victoria The rust from the nails alters the soil pH which causes the effect you mention, it is grounded in good science! Can you elaborate on that? I thought rust was iron oxide, which I thought was alkaline, but hydrangeas go pink, not blue, in alkaline soils. Are you sure it's a change of pH that's having the effect, rather than greater availability of iron? From a website: http://www.nobleplants.com/articles/...0history%20&%2 0cult ure/care%20&%20culture.html snip explanation of availability of aluminium depending on pH OK - that's fair enough ... but where does the iron come in? Or did I miss something? I have not yet read the URL referred to up above here, but I would be most surprised if it said that bluing of Hydrangeas is very seriously connected with Aluminium. My understanding is that it is primarily the availability of the correct ion of Iron which determines the bluing. Iron exists in two ionic forms, one of which is involved in the blue dye of Hydrangeas. In the wrong kind of soil, the desirable ion is rapidly converted into the wrong one, thus preventing the blue dye from be synthesised in the plant. Franz |
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