Given that the hydrangea is an acidophilic plant, it can be said that a pH of 4.5-5 will favor the coloring in blue, purple or white, while with a pH 6-6.5 we will get pink or red hydrangeas.
It is possible, in soils with neutral reaction, to administer aluminum sulphate to obtain a coloring in shades of blue or, in acid ones, to add calcium carbonate to obtain pink or red. In addition to the components of the soil itself, what affects the pH is also the hardness or otherwise of the waters: fresh water lowers them.
However, the best principle remains to favor the coloration naturally determined by the composition of the soil in which we find ourselves: to cultivate then pink hydrangeas red or white in calcareous and alkaline soils in the presence of hard water; blue, purple or purple hydrangeas in acid soils or in the presence of fresh water. By doing so, the shades will remain unaltered and intense, without the need to administer any additional products.
Even with regard to fertilization, hydrangeas are not demanding plants and it would be enough to carry them out in spring.
However, since they require a lot of water and the washing is therefore considerable, further fertilizations are recommended (monthly) in the summer period. The alternative is to use, in spring, a slow-release fertilizer (six months).
A good universal will be more than sufficient, obviously respecting the color of the plant: therefore low phosphorus and high potassium content for blue hydrangeas, normal balanced fertilizer for red or pink. Mulching, which will allow to keep around moisture and the necessary fresh, is to be carried out in spring with leaves, peat, compost, manure or bark of trees. Hydrangeas are sturdy plants, have few enemies and are ill. More than from actual diseases or harmful insects, the greatest risks are caused by the cold winds in late spring, by incorrect plantations, excessive pruning and by scarce care by man.
Hydrangeas coloring: White hydrangea
The varieties of hydrangea are different and each of them is characterized by particular flowers, which take on different colors. Some varieties, then, are distinguished by the white color of the flowers, such as the hydrangea quercifolia, a shrub species with plants that reach a meter in height, or the hydrangea paniculata, which, on the other hand, can reach up to 6 meters in height .
The white hydrangea, unlike other varieties, maintains its color over time, without changing, even when the soil has different characteristics as regards the composition.
The cultivation of white hydrangea does not present greater difficulties than plants that have other colors, except that the flowers can be more delicate and can stain more easily.
Hydrangeas are hardy and resistant plants, which however need to be placed in partially shaded places, so that they can be protected during the hottest hours of the day, especially during the summer season, when the sun's rays are very intense. Another very important aspect for the health of these plants is proper watering, as these plants tend to suffer in the event of drought.