I shall make no attempt to make this page look attractive - it ought to be a note-book, frequently corrected.
The first thing to do is to say that I have not measured pH in pots or shrub-beds, and the blueing of colours in both may be limited by phosphate from general fertilisers, which were certainly used in both situations. The shrub beds were generously fed with humus and “growmore” and acidified with ferrous sulphate. The treatment was done as uniformly as possible, and I am so eager to avoid any bush with a mixture of colours that I have not done any top-dressing for fear of doing it unevenly - apart, that is, from an annual scattering of chicken-manure pellets.
Although all the suppliers of the plants had used peat-based composts, those were probably general-purpose neutralised mixtures. Certainly the first flowers of each sort were the reddest that that sort has since produced, either in pots or in shrub-beds.
Most of the 1998 arrivals were slipped, and the resulting rooted cuttings had been repotted more than once before flowers appeared, the plants being clearly older at that stage than the originals were when they were supplied. In general the flowers were red or pink at first, and each year they showed a bluer colour than in the preceding year.
Shape is generally a poor guide to identity. As the flower heads age their conformation can alter significantly - see the Hatfield Rose page. More minutely, sepals themselves change shape as the season advances: in Hatfield Rose they can shift from oval to rhomboid, in Hamburg they can develop pointed tips. The most unexpected observation has been that young plants often, usually, produce smooth-edged (‘entire’) sepals: most grow up to produce more or less serrated sepals: perhaps those that have not done so (see Parzifal) are just not old enough yet?
Any and all comments on the hydrangeas will be gratefully received and acknowledged - please do email me at email@example.com