Passionate About Plants

Paul lets us into the secret of getting a blue hydrangea

Getting the Blues!

By the time you are reading this we will have been once again to the Royal Norfolk Show having a stand in the Horticultural Marquee, where we display our wide range of Hydrangeas. If previous years are anything to go by our blue Hydrangeas will be a big talking point. Questions range from how do you get blue Hydrangeas? To why did my blue one turn pink? Really it's all one question why do Hydrangeas turn blue?

So you want a blue Hydrangea! I will now let you into the secret.

Forget about sticking rusty nails in the ground although a soil with iron is good, a soil with aluminium sulphate is more important. For most cultivars the natural flower colour is pink even on slightly acid soil, the key factor in flower colour is not just the acidity of the soil but the plants accessibility to aluminium ions within the soil. This is usually in the form of aluminium sulphate. A Hydrangea growing in acid soil without aluminium sulphate will not bear blue flowers neither will a Hydrangea turn blue if the soil it is growing in has aluminium sulphate but is basic or alkaline, the higher the pH the more the calcium in the soil will bind with the aluminium sulphate so as to 'lock it up' thus making it is unavailable to the plant.

Having said that it is possible to grow Hydrangea hortensia cultivars with blue flowers, even in non acidic soils (a natural pH above 4.5,) by adding aluminium sulphate to the soil, it is equally important to choose a cultivar that turns blue easily, such as Queen Elizabeth. As general rule; red cultivars remain red or purple red never turning a good blue, white flowers usually retain their colour on any soil type. Pink will turn varying degrees of blue when treated. There are always exceptions to any rule so I would rely on the knowledge of a good nurseryman when choosing a plant to turn blue.

A few Hydrangeas for the plantsman and keen gardener.

arborescens 'Annabelle'

The flowerheads of this variety are extremely large and pure white resembling a mop head. Although this shrub can grow a little untidy it can easily reach 1.25m high it is worth staking when growing it and you will be rewarded by some of the biggest blooms I have seen on a Hydrangea a real must for the garden.

macrophylla (hortensia group - Mop heads) 'Jofloma'

A medium sized new variety with a lovely yellow foliage and large white flowerheads. I originally had my doubts as to whether it would look good yellow and white together but when grown well it is very impressive (looks better than it sounds).

macrophylla (lacecap group) 'Geoffery Chadbund'

A compact shrub up to 1.5m high, the flowerheads are rounded and the ray flowers are arranged in a single ring, florets are a dark rosy red the sepals are entire. This is my favourite lacecap, which I first came across at Barcock's Nursery in Suffolk in the early 70's.

paniculata 'Burgundy Lace'

This slow growing shrub bears pyramidal white flowers common with all paniculata's. Paniculata's can form large shrubs or even small trees but this is a good garden variety, the small white flower panicles turn to wine red in the autumn.

quercifolia

There are many cultivars of this American species most of which originate from the United States, but the species form is a very good garden plant. The common name Oakleaf Hydrangea describes the leaf shape and in common with its namesake the American Red Oak it also has fantastic autumn tints of red.

There are many more species and hundreds of cultivars of which we have a selection of over 50 types that we aim to propagate at the nursery. Hydrangeas are one of my favourite garden plants so I am on the constant look out for new and interesting types be they species or cultivars. We have many of them for sale at the nursery and we will also be selling them at the Sandringham Flower Show on Wednesday 30th July, I look forward to seeing you there.

Happy gardening.

Paul Markwell,

Quaymount Nursery,

01366 500691.

Paul Markwell,