Flower color intensity (was Soils and flower color)

Nathan Lange plantsman@comcast.net
Tue, 12 May 2015 14:13:15 PDT

I had a similar experience with the Itoh Paeonia 'Scarlet Heaven' 
which was a stunning deep red before moving the plant here where the 
flowers are now more rose-red. In this case, the most obvious 
difference between locations was the night temperature, with of the 
first location being generally cooler during flowering than here. 
Lower temperatures increase flower color intensity of most species. 
High temperatures usually have the opposite effect.

While temperature can be the most important environmental factor in 
determining the intensity of petal pigmentation, there are also many 
other important factors in play such as soil composition, 
fertilization, pH, and light. The color intensities of some cut 
flowers (both dicots and monocots) benefit greatly from being treated 
with potassium or magnesium. High iron concentrations have been 
correlated with increased pigmentation in petal tissue. In fact, 
foliar applications of iron have been used to improve the flower 
color of Chrysanthemums. There are likely many other examples of 
mineral nutrient foliar sprays benefiting flower color. The 
anthocyanin content of peony flowers can be affected by pH with lower 
soil pH conditions known to result in lighter peony flowers.

Not surprisingly, low light levels result in more faded flowers. 
Light quality is also important, although generally not controllable, 
with the higher ultraviolet light levels at higher elevations 
creating more petal pigmentation. Longer photoperiods can decrease or 
increase petal pigmentation depending on the photoperiodism of the species.

So, all other things being the same, Jane's change in iron and/or 
potassium levels could be the cause for the faded peony flowers. 
Jane, please report back if you are able to change the flower color 
intensity with supplemental iron and/or potassium. Maybe I can change 
the flowers on my 'Scarlet Heaven' peony as well.


At 08:21 AM 5/12/2015, you wrote:
>Moving many mature plants from one garden to another three and 
>one-half years ago seems to have altered the flower color in some. 
>Soil in the first garden is very well drained. rocky,  volcanic 
>"shot clay" with high iron and potassium levels. That in the new 
>garden is fairly heavy clay (also of volcanic origin but at lower 
>elevation), now well amended with organic matter, with none of the 
>red color seen in the former. Two species of Paeonia, both grown 
>from wild-collected seed in the mid-1990s, are particularly 
>different. Paeonia mlokosewitschii was cream with a pink flush, 
>mostly from pink veins; now it is clear pale yellow. Paeonia 
>officinalis was a beautiful blood-red; now I would call it rose-red, 
>a less striking color.
>Have you noticed other geophytes that vary in flower color in different soils?
>Jane McGary
>Portland, Oregon, USA

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