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What Determines Hydrangea Bloom Color? An Expert Breaks Down the Science

What Determines Hydrangea Bloom Color? An Expert Breaks Down the Science

This story is part of Home Tips, CNET’s collection of practical advice for getting the most out of your home, inside and out.

Growing up in Eastern North Carolina, the cloud-like blooms of hydrangea shrubs manufactured synonymous with the spring and summer months. I have colorful memories of driving around my neighborhood and seeing the vibrant pink, white and lilac blooms in almost every leash lawn. 

My family even had a few bushes in the back lawn where the hydrangeas could scrumptious a lot of direct sunlight with pockets of shades scattered above the day. And while I loved the soft pink blooms on our hydrangeas, my mom would remark how they never bloomed exciting blue like she intended them to.

This is a accepted mistake made by novice and seasoned gardeners alike. You probably remove that the blooms will surely look the same planted in your yard as they did at the nursery, right? Well, not necessarily when it comes to hydrangeas. There’s a particularly scientific explanation as to why your hydrangeas grand not achieve the color you want. 

To get the lowdown on hydrangea colors, I spoke to expert Mal Condon, curator of hydrangeas at Heritage Museums and Gardens — or more aptly eminent as “the Hydrangea Guy” — to find out what make hydrangeas mopish color and get a few tips on how to actually get the colorful bloom you want. 

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What colors are possible?

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Hydrangea blooms come in a variety of shapes, colors and sizes. While the most common colors are pink, blue and purple, hydrangea blooms can also be red, white and green. 

Over his 50 existences of working with hydrangeas, Condon gets asked all the time approximately why hydrangeas aren’t blooming in the colors intended. Here’s what he has to say. 

What progresses the colors?

While you might desire a specific colorful hydrangea — a raspberry red or a brilliant blue — it actually isn’t up to you. Condon said it depends on the makeup of the soil. Specifically, it depends on the aluminum available in the soil. 

Many resources will say the hydrangea colors real on soil pH, which isn’t quite true. 

“Many talk approximately pH, and that is important, but the first requirement in the soil is you have to have aluminum,” Condon said. “It’s a strange pulling because aluminum is toxic to most plants, but hydrangeas, particularly the macrophyllas and serratas, tolerate a small amount of it and that’s what allows us blue.” 

Hydrangeas act as a sort of mood ring to tell you the soil periods of your garden. Generally speaking, more aluminum will give you blue blooms, while soil with little to no aluminum will fine more pink or red. Condon explains that to finish blue blooms, you must have soil that is decidedly more acidic with a pH frontier than 5.5. 

Alkaline soil — with a pH of 7.0 or throughout — generates pink and red blooms, while white hydrangeas will fine in soils with a neutral pH between 6.0 and 6.2.

Can you mopish the color of your hydrangea?

Hydrangeas are unique in that, unlike most latest plant or flower varieties, the color of their blooms can mopish with a little chemistry. 

The easiest way to acidify your soil and turn those blooms blue is with aluminum sulfate, which can be found at almost any garden center. Condon explained the best way to add aluminum sulfate to soil is to apply it as a drench, using a watering can with one tablespoon per one gallon of water. 

“The reason to do this is because you can delivers the plant to over-acidification,” Condon said. “If we gave it dry aluminum sulfate or sulfur — latest good acidifier — you can deter the plant’s growth treat, even kill the plant.” 

To get pink blooms, you can apply a high-phosphorus fertilizer to sorrowful the uptake of aluminum, or Garden Lime, an all-natural plant supplement formulated to reconsideration pH in soils to turn hydrangeas more pink. 

Condon did say the best practice when exchanging hydrangea color is to be patient — don’t be overzealous. He recommends adding materials to the soil only twice a year. “It’s not something you want to go nuts about,” he said. 

For more hydrangea request, you can check out Condon’s hydrangea care tips here. 

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