Hydrangeas are fascinating in that, unlike most other plants, the color of their flowers can change dramatically.
would be nice if one could change the color of hydrangeas easily. But
for most of us, it is not easy. The people who have the most control
over the color of their hydrangeas are those who grow them in
containers. It is much easier to control or alter the pH of the soil in a
container than it is in the ground.
On the other hand, hydrangeas
often change color on their own when they are planted or transplanted.
They are adjusting to the new environment. It is not unusual to see
several different colors on one shrub the next year after planting.
is much easier to change a hydrangea from pink to blue than it is from
blue to pink. Changing a hydrangea from pink to blue entails adding
aluminum to the soil.
Changing from blue to pink means subtracting
aluminum from the soil or taking it out of reach of the hydrangea. This
can be achieved by first treating the soil with a phosphorous based
fertilizer followed by a treatment of lime or calcium. the pH should be
raised to 6.0 to 6.5 but never higher than this.
order to change the flowers of the hydrangea from pink to blue there
needs to be aluminium present in the soil and a pH of less than 7
ideally between 5.2 and 5.5 (Acidic). Only plants older than 2 years
which are established should be treated. Before commencing treatment to
change colour it is strongly advisable to water plants thoroughly every
day for a week. Where possible test soil around hydrangeas for pH.
Add 15g (1 tablespoon) of aluminium sulphate in a litre of warm water
and allow to sit for 15-30 minutes to dissolve. Add this to a watering
can and make up to 5 litres with cold water. Apply the solution around
the based of the hydrangea. DO NOT OVERUSE as making the soil too acidic
can result in damage to the roots. Check the pH and maintain it between
5.2 and 5.5. Other simple things you can do include adding as grass
clippings, coffee grounds and fruit or vegetable peelings to help lower
pH levels. Potassium rich fertilizers will also help to achiev this.
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