Hydrangeas

Hydrangeas are a classic old fashioned plant. The most common type is the mophead (H. macrophylla), which huge ball like clusters of pink or blue (or somewhere in between). The coloured parts are actually bracts, or modified leaves and the flower is the teeny tiny little bit at the centre.

See the tiny bud in the centre? That’s the unopened flower. The white and purple surrounds are termed ‘bracts’.

Hydrangeas are also magical plants that change their colour based on the level of aluminium in the soil. The amount of aluminium available for uptake by a plant is affected by the soil pH - the lower the pH (or the more acidic), the more aluminium can be absorbed by the plant and the more blue in colour it becomes. In alkaline soils, the aluminium is chemically bound tighter to the soil particles and not as available for the plant to absorb, and the flowers turn pink. So for blue hydrangeas you need two things: aluminium and acidity. You can lower the pH of your soil by adding ammonium sulfate, and you can increase the aluminium content using a ‘blueing agent’ (aluminium sulfate). Conversely, you can raise the pH (for pink hydrangeas) by adding garden lime. But don’t try this on a white hydrangea! White hydrangeas have no pigments and won’t change.

My original plant.

A few years ago I bought a bicolour hydrangea that was white around the edges of each bract and purple in the centre. It died while we we were away and I didn’t get to water it and I have been on the hunt for another one ever since. I finally found one online and it arrived in the mail this week! Plant mail is the best mail. I’ll put it in the ground soon and we’ll see what happens to the flower colour.

Plant mail is the best mail. And I’ve never had such a lush plant delivered by mail before! The flowers will colour up as they develop.

One more thing - despite always seeing huge hydrangea bushes planted at the foot of old weatherboard houses, they have a bad reputation for attracting termites. So play it safe and plant them up the back. They’ll thrive in a fertile, well drained soil (like the volcanic soils of the Azores!), with a little bit of shade from the hot afternoon sun.