Getting the best blues in your hydrangeas

April 4, 2022
  • Whastsapp

Every season, we’re surprised by the number of hydrangea introductions from breeders. As Dr. Fred Hulme, our Director of Technical Services, remarks, “There’s this continuing stream of genetics coming in.” From lime green or strawberry pink to cool creamy white or multi-colored purple hues, hydrangeas are in demand. But despite the diversity of color, brilliant blue blooms still win sales. In the past, getting peak blues ready for retailers wasn’t easy. But ICL’s Osmocote Blue-Max changes that.

The key to blue hydrangea blooms

Many popular hydrangea cultivars have the capacity for dramatic changes in flower color. Fred recalls, not so long ago, when many growers thought acidic soil was enough to make pink blooms blue. It’s true that low soil pH plays a role in enhanced blue color. But that desirable shift depends on sufficient soluble aluminum (Al) in the growing media. Timing is also key to the blue blooms consumers crave.

Fred breaks it down this way: “The biology there is you have to have enough soluble aluminum at the point when the flower buds have formed. Before they even break dormancy and develop, you need to get enough aluminum in the tissue.” Then blue pigment forms in the flower buds of hydrangeas capable of the change.

While acidic growing promotes blue flowers, high growing media pH makes aluminum less available—even when it’s present in sufficient quantity. And, if you have excess phosphorus in the soil solution, it can tie up aluminum and prevent its uptake. In both cases, that means purple to pink blooms instead of blue. That’s where our Blue-Max coated aluminum sulfate can help.

Blue-Max to the rescue

ICL developed Blue-Max to make it safer, easier, and more profitable for your growing operation to produce beautiful blue hydrangeas. With a single application of Blue-Max coated aluminum sulfate, you can deliver a sustained aluminum (Al) supply to your hydrangea production. And with Blue-Max, the benefits persist long after the plant leaves your dock.

Blue-Max is designed to deliver a slow and steady supply of aluminum to the hydrangea root system over the course of two to three months. This gives you much greater flexibility on when to apply the product, ensuring your plants get what they need to trigger bluing—when they need it. Plus, because Blue-Max is coated, it’s safer and less wasteful compared to traditional, time-consuming, labor-intensive approaches to blue blooms.

Many growers know traditional bluing methods can be ineffective and fail to deliver blue blooms. But, as Fred notes, some methods can also leach aluminum into the environment or even injure plants and burn roots and leaves due to high soluble salts and aluminum toxicity. With Blue-Max’s polymer-coated E-Max Release Technology, aluminum sulfate and essential micronutrients are safely and steadily delivered to plants, without excessive soluble salts. Blue-Max can also lower media pH to help soluble aluminum remain available to plants and bring the blue you need.

Best management practices for Blue-Max

With Blue-Max coated aluminum sulfate, the key objective is to supply critical aluminum concentrations to developing blooms at the right time. For nursery crops, optimal application times are during any period of flower development or during late winter/early spring just as buds break dormancy. Fred notes that some growers have had success intensifying blue color with split applications: one application in fall as plants approach overwintering, plus a follow-up application in late winter/early spring.

As a general rule, we recommend using higher rates of Blue-Max for older established plants, high-bark media, root zone pH above 6.0, and high-phosphorus fertilizer programs. You’ll typically want to use lower rates with freshly potted plants, high peat-based media, root zone pH below 6.0, low-phosphorus fertilizer programs, sub-irrigation, and other aluminum treatments.

Before full adoption of a Blue-Max bluing program, we recommend trialing different rates to determine the optimal rate for your specific growing operation. Your ICL Territory Manager is ready to help with that. As with all new products and practices, effective rates for your program will depend on many factors—from crop condition and growing environment to cultivar type, fertilizer program, growing media, and more. We’re here to help sort that out.

At ICL, we strive to help you grow the best possible plants and grow your business as you do. Our products are designed to make that road safer, easier, more sustainable, and more profitable for you. If you’d like to learn more about Osmocote Blue-Max or other ways that ICL’s people, products, and services can help you succeed, give us a call. We’d love to hear about your business and your needs.