Letter to the editor 2, Oct. 16, 2014
James Parry’s latest horticultural chronicle (The English Gardener, Your Local Journal, October 9) about turning Pink Hydrangea to blue could include the gender or species and cultivar as well as soil Ph. Hydrangea Annabelle ‘Invincible Spirit’ from the ‘Proven Winners’ series will always be pink, will not turn blue no matter how many pennies are turned into the soil.
This cultivar was developed in recent years. http://www.hydrangeashydrangeas.com/inv_spirit.html
However, cultivars such as Hydrangea Macrophylla pink (pH6,5) need an acidy soil to become blue, something like pH 5,. Therefor a soil amendment with mulch, and/or peat moss containing potassium and phosphorus elements will create the necessary environment for blue flowers. Some add a sulfate but it’s not always needed. In Portugal Island, agricultural farmlands are edged with blue Hydrangeas.