{"id":105039,"date":"2026-02-11T15:10:23","date_gmt":"2026-02-11T14:10:23","guid":{"rendered":"https:\/\/klasmann-deilmann.com\/?p=105039"},"modified":"2026-02-11T15:10:23","modified_gmt":"2026-02-11T14:10:23","slug":"the-art-of-hydrangea-cultivation","status":"publish","type":"post","link":"https:\/\/klasmann-deilmann.com\/en\/the-art-of-hydrangea-cultivation\/","title":{"rendered":"The Art of Hydrangea Cultivation"},"content":{"rendered":"

\"\"<\/strong><\/p>\n

Horticulture Guido Sonneville masters the Art of Timing and Substrate<\/strong><\/p>\n

Behind the spectacular bloom of a hydrangea lies a meticulous process shaped by generations of horticultural knowledge, careful substrate choices and precise planning. At Horticulture Guido Sonneville in Destelbergen, Belgium, these plants spend up to eight months in cold storage\u2014an invisible but crucial phase in their development. This story takes you into a world where roots matter more than flowers, and success is measured in subtle variations of soil and timing.<\/p>\n

Five thousand carts of plants disappear into cold storage in November. They endure up to eight months of cold temperatures, as delivery to the forcing facility continues until June of the following year. Between those two moments lies a story of experience, precision, patience\u2014and just the right substrate.<\/p>\n

Guido Sonneville (61) walks between the rows of hydrangeas in Destelbergen. Together with his wife Rita (62) and son Thomas (30), they run a business now in its fourth generation. \u201cMy grandfather started the business after the First World War. He watered everything by hand and delivered plants in Merelbeke with a dog cart. Today, we produce one and a half million hydrangeas per year and export them across Europe and beyond.\u201d<\/p>\n

This scale-up demands precision at every level. The substrate, in particular, plays a key role when plants are stored for months without a drop of water.<\/p>\n

Different Soils, Different Roots<\/strong><\/p>\n

\u201cWe use different substrates because we grow in different ways,\u201d Guido explains during a tour. \u201cPlants in container fields with foil grow differently than those in pots on open ground. In the sandy soil around Destelbergen, hydrangeas develop a thicker root system. That sandy soil gives them a little extra. When we grow in container fields, we need to compensate for the lack of sandy soil by adapting the substrate.\u201d<\/p>\n

Bart Claessens from Klasmann-Deilmann adds: \u201cIn open ground, sandy soil draws moisture from the pot base. In container fields, fine and heavy substrates can cause oxygen deficiency at the roots. A lighter mix is better here.\u201d The Sonneville family tests new substrates actively. \u201cIn recent years, we\u2019ve run trials with peat-free substrates. Keeping all other variables constant, the differences become clear\u2014both in colour and in leaf quality.\u201d<\/p>\n

Bart agrees: \u201cYou can spot the dividing line instantly. Plants in heavier, compost-rich mixes are darker. It\u2019s a vivid example of how hydrangeas respond to substrate composition\u2014and how cultivation changes entirely with just one variation.\u201d<\/p>\n

Collaboration Since 2003<\/strong><\/p>\n

The search for the perfect substrate brought Guido to Klasmann-Deilmann in 2003. \u201cOver the years, we\u2019ve tested many combinations. Adjusting the mix with more or less white peat, more or less clay\u2014it\u2019s a continuous process of fine-tuning.\u201d Bart adds: \u201cGuido and Thomas use a rather unique mix compared to others\u2014lots of compost and loamy clay. It\u2019s quite traditional and suits hydrangeas well.\u201d<\/p>\n

Guido explains: \u201cHydrangeas grow large and tall, so we need stability in the pot. The substrate must hold moisture throughout the cooling period.\u201d Bart continues: \u201cThe last plants of a season can spend eight months in cold storage\u2014no leaves, no evaporation. If the substrate dries out, root tips will be damaged. We need a structure that holds moisture long-term. That\u2019s the challenge.\u201d<\/p>\n

From Pink to Blue<\/strong><\/p>\n

Hydrangeas are known for their striking colours, and that\u2019s no accident. Guido points to a field: \u201cWe\u2019re \u2018bluing\u2019 these plants by changing the soil\u2019s pH\u2014not through the substrate, but by adding aluminium sulphate to the water. It\u2019s how we turn pink to blue. White stays white, and red stays red.\u201d<\/p>\n

\u201cBut the plant leaves here without flowers,\u201d adds Thomas Sonneville with a smile. \u201cWhat matters most is the root system. The fewer flowers at this stage, the better.\u201d It may sound counterintuitive, but the flower buds are already visible in autumn\u2014if you know where to look.<\/p>\n

Timing is Everything<\/strong><\/p>\n

The root system is crucial because hydrangeas are incredibly timing-sensitive. It takes nearly two years to grow from a cutting in February to a blooming plant, but there’s just a one-month window to ensure optimal branching. \u201cBetween 15 June and 15 July, we top all the plants,\u201d Guido explains. \u201cThis creates a beautiful, full shape. Some varieties are topped once, others twice, but after that, there\u2019s no more structural adjustment possible.\u201d<\/p>\n

Cooling must be just as precise. \u201cHydrangeas need at least 40 days of cooling\u2014about 1,000 hours. This can occur naturally or in refrigerated storage. We prefer to control it. From October, they go into the refrigerator, where we add ethylene gas to trigger leaf fall. The result looks like a tiny Christmas tree without needles.\u201d<\/p>\n

From there, the international market takes over. \u201cScandinavia prefers compact varieties because of high energy costs. In Turkey, size matters\u2014they like mass and volume.\u201d<\/p>\n

Back to Basics<\/strong><\/p>\n

While peat-free alternatives are gaining attention, Guido reflects on the past. \u201cMy grandfather made his own substrate: azalea soil, cotton, and manure, layered and rested over winter. But those were different times. He also watered everything by hand!\u201d<\/p>\n

Today, the family continues to experiment with innovations like Growcoon. \u201cAnything that strengthens the root system is worth exploring.\u201d Thomas, representing the fourth generation, sees this blend of old and new as essential. \u201cWe have loyal customers who trust our knowledge. But that doesn\u2019t mean we can stand still. We always have to think ahead.\u201d<\/p>\n

That foresight is measured in years, not months. \u201cIt takes two years for decisions about substrate or cuttings to show up in flowers,\u201d says Guido. \u201cSo we watch market trends and plan ahead. But we\u2019ve learned one thing: healthy roots in the right substrate are always the key.\u201d<\/p>\n

\"\"<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Horticulture Guido Sonneville masters the Art of Timing and Substrate Behind the spectacular bloom of a hydrangea lies a meticulous process shaped by generations of horticultural knowledge, careful substrate choices and precise planning. At Horticulture Guido Sonneville in Destelbergen, Belgium, these plants spend up to eight months in cold storage\u2014an invisible but crucial phase in their development. This story takes you into a world where roots matter more than flowers, and success is measured in subtle variations of soil and<\/p>\n","protected":false},"author":14,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[291],"tags":[],"class_list":["post-105039","post","type-post","status-publish","format-standard","hentry","category-competencies"],"acf":[],"yoast_head":"\nThe Art of Hydrangea Cultivation - Klasmann-Deilmann<\/title>\n<meta name=\"description\" content=\"Behind the spectacular bloom of a hydrangea lies a meticulous process shaped by generations of horticultural knowledge, careful substrate choices and precise planning.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/klasmann-deilmann.com\/en\/the-art-of-hydrangea-cultivation\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The Art of Hydrangea Cultivation - 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