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WikiProject Plants (Rated Start-class, Mid-importance)
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I'm thinking of purchasing some Hydrangea Macrophylias of different colours.

Do these flowers start off at a height of 4 foot or are they much smaller?

Nick —Preceding unsigned comment added by (talk) 19:28, 28 July 2009 (UTC)

Nick--this talk page is reserved for discussions about the content of Wikipedia's Hydrangea page. There is a forum web site that would better meet your needs: [1].Pinethicket (talk) 21:55, 28 July 2009 (UTC)

Clarification of pruning and subsequent flowering timing[edit]

I am "reporting" a confusion to the reader (me). I do not know the correct information, but my point is that my desire for the information was not addressed by the currently present text.

Under "Cultivation and uses"

..... Some are best pruned on an annual basis when the new leaf buds begin to appear. .... Other species only flower on 'old wood'. Thus new wood resulting from pruning will not produce flowers until the following season. ....

It is very important to know which "some" are and which "other" are. It would be great if someone who knows this information and/or can provide links to the information could contribute it.

JaySmithWiki (talk) 14:15, 5 May 2011 (UTC)

JaySmithWiki, I think this USDA page found in the references could provide you enough information to make some edits, if you were inclined, or at least give you some additional info. -- (talk) 17:21, 8 July 2011 (UTC)

Colors and Acidity Section[edit]

The article references this USDA page, which says the following about color and acidity:

Flower color in H. macrophylla is dependent on cultivar and aluminum availability. Aluminum is necessary to produce the blue pigment for which bigleaf hydrangea is noted. Most garden soils have adequate aluminum, but the aluminum will not be available to the plant if the soil pH is high. For most bigleaf hydrangea cultivars, blue flowers will be produced in acidic soil (pH 5.5 and lower), whereas neutral to alkaline soils (pH 6.5 and higher) will usually produce pink flowers. Between pH 5.5 and pH 6.5, the flowers will be purple (see image at left) or a mixture of blue and pink flowers will be found on the same plant.

Looking at the other citation, from U of Georgia:

Research has determined that the actual mechanism of color variation is due to the presence or absence of aluminum compounds in the flowers. If aluminum is present within the plant, the color is blue. If it is present in small quantities, the color is "in between," and if it is absent, the flowers are pink.

Soil pH indirectly affects flower color by affecting the availability of aluminum in the soil. When the soil is acid (pH 5.5 or lower), aluminum is generally more available to the roots. When the soil is neutral or alkaline (pH 7.0 or higher), the availability of aluminum is decreased and flowers are more pink.

Both resource seems to contradict the claim of "very pale cream petals" for neutral pHs (in H. macrophylla), yet are used as citations. I wanted to note this before making changes, in case there's something I'm missing (I'm not exactly a flower biochemistry buff). -- (talk) 17:21, 8 July 2011 (UTC)

I'm also not an expert, but it clearly depends on what other colors are produced by the plant. If it's not making any red pigment, then without blue it will be cream; if it does, it will come out pink. So they're not entirely contradictory, it's just that red is controlled independently of the pH. KarlM (talk) 19:05, 10 July 2011 (UTC)