Improving the modern cut Hydrangea

Industry veteran, and former FCI publisher, Jaap Kras provides valuable insights into the genus of Hydrangea, its origins, and the breeding work in cut Hydrangeas, including many goals, particularly shelf life.

Jaap Kras

“Hydrangea, aka Hortensia, is a genus of nearly 100 species of flowering plants. Hydrangeas are native to East Asia (China, Korea, and Japan) and America, thriving in mostly mild to cold areas.

Most species are tall shrubs standing 1-3m (3 ft-3 in). Some are small trees, and others are lianas reaching up to 30m by climbing up trees. There are deciduous and evergreen Hydrangeas.

The widely cultivated temperate species are deciduous. The genus includes many cultivars that are commercially grown. I counted 42. The most important varieties are from Hydrangea macrophylla.

The word Hydrangea is derived from the Greek translation of ‘water vessel’. For gossip lovers: some say ‘Hortensia’ is a Latinised version of the French name Hortense honouring the French astronomer and mathematician Nicole Reine Hortense Lepaute. Others sustain that the plant is named after Hortense de Beauharnais, daughter of the French Empress Joséphine de Beauharnais. (By the way, this cannot be true because the plant was named before she was born.) Others argue the plant is named after Hortense van Nassau, daughter of Karel Hendrik Nicolaus Otto Prince of Nassau-Siegen, an explorer who travelled the globe. (The attentive reader will understand that I prefer the last explanation as a born and bred Dutchman.)

Hydrangeas produce flowers from early spring to late autumn, growing in flowerheads on a stem. Two types of flowers are small non-showy fertile flowers in the centre of the flowerhead and large sterile showy flowers with large colourful sepals. Plants in wild populations have few to no showy flowers.

Cut Hydrangeas dehydrate easily and wilt very quickly due to the large surface area of the petals. A wilted Hydrangea may have its hydration restored by first having its stem immersed in boiling water as the petals can absorb moisture; the petals may then be immersed in room temperature water to restore the flower’s hydration.

Breeders are well aware of the vase life issue of cut Hydrangeas and breed varieties with a longer vase life using interspecific breeding, crossing Hydrangea macrophylla with H. serrata, H. arborescens and H. paniculata cultivars.

Soil pH affects a Hydrangea’s colour. Blooms come in deeper shades of blue when the soil is more acidic. A more basic alkaline soil will result in pink-hued flowers, and a neutral soil will give way to purple/pinkish blooms.

In most species, the flowers are white. Hydrangea macrophylla is mainly used as a cut flower featuring blue, red, or purple, with colour saturation levels ranging from pale pink, lavender, powder blue, purples, Bordeaux, and deep blue.

Most Hydrangeas flower on one-year-old branches, but newer varieties from Hydrangea macrophylla also flower on older and new branches.

Hydrangeas are a very popular cut flower worldwide. The most important production countries are Colombia, with a production area bigger than 1,000 ha. (1 acres is 0,40 ha), China has more than 500ha; the Netherlands has over 100ha. Italy, Japan, Ecuador, Kenya, and the USA are also important cut Hydrangea producers.

I had the pleasure of receiving help for this column from Andrea Mansuino, former president of CIOPORA. He is also an internationally well-known fourth-generation breeder of ornamentals. He owns Mansuino srl, which began breeding Hydrangeas in Italy 12 years ago. He developed a project cooperating with a research institute in Tuscany, Pescia-based CREA-OF.

The main targets of this programme, run by conventional breeding in San Remo and through biotech support in the labs in Pescia, are to improve the modern cut Hydrangea. Productivity, stem length, quality, flower size, shape, colour, and vase life are standard goals. Mansuino and his researchers are also looking at targets such as low requirements of cold for flower induction, drought tolerance and recurrent blooming.

The idea is to obtain new varieties that can be commercially grown in warmer climates, targeting a ‘Mediterranean Hydrangea’- a tropical Hydrangea for countries such as Kenya, Colombia, and Ecuador. This breeding work is reminiscent of the ‘Mediterranean carnation’ that the Mansuino family developed in the last century.

Interspecific breeding is part of the programme. Trials are happening at partner farms in Kenya, Ecuador, Colombia, and China. A positive side effect is the development of Mediterranean and tropical cultivars of pot production. Due to global warming, the vision is timely, and the first varieties will be introduced under the brand name Azzura.H.”

This article first appeared in the June 2023 edition of FloraCulture International.