Turns out, alum powder may be the secret to keeping your hydrangeas perky.
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blue hydrangeas in vase
Credit: Getty / Patti Chronert

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Have you ever snipped some fresh flowers from your yard, only to have them look sad and wilted hours later? (Guilty!) My hydrangea bush just started blooming, and while I was searching for the best way to keep my flowers fresh after cutting them, I saw that several websites recommended using alum powder. 

But first, what is alum? According to McCormick Spices, alum (or potassium aluminum sulfate) is a food additive used in pickling and canning to help keep vegetables and fruits crisp. It’s pretty common—you can find it in the spice aisle at your local grocery store or pick up specialty versions on Amazon.

J Schwanke, flower designer, award-winning author and the host of J Schwanke's Life in Bloom on PBS, says you can make hydrangeas last longer by cutting the stem and dipping the end in alum powder  before placing in water. Schwanke said, "I'm a fourth-generation florist, and it's [a trick] my grandfather told me about." He explained, “The coating of alum makes the hydrangea draw more water." 

I also called Dorothy McDaniel from Dorothy McDaniel’s Flower Market in Birmingham, Ala. to get the scoop. She said, “I’ve heard people say that before [about alum and hydrangeas], but I’d want to know a little more about it.”

While McDaniel says she can’t recommend alum powder because she’s never tried it, there are a few things she says that can keep your cut flowers fresh. First, she says, “Make a sharp, angular cut [at the base of your flower] with clippers that are used only for cutting flowers. Then, re-cut them every 3-4 days and place them in fresh water.”

She also recommends using flower food—which you can buy from any florist—to help reduce the bacteria in the water. McDaniel says if you’re looking for a DIY solution, you can also use a drop—and she emphasizes a literal drop, not more—of Clorox in a gallon of water to reduce bacteria buildup. Her last bit of advice? Don’t ever have your greenery submerged in the water, because the leaves can get soggy and fill the water with unwanted bacteria. You can keep leaves above the water’s surface level, but snip any greenery on stems that falls below the water line.

Since the pros have mixed feelings on alum powder, I decided to try it out for myself. I went into my backyard, snipped a hydrangea, cut it at a 45-degree angle, removed the extra greenery and dipped the end into alum powder. Then, I placed it in water and waited a couple hours. Here are the before and after photos. (The pic on the left is the flower straight from the bush; the one on the right is the same flower after about two hours with alum and water.)

hydrangeas and alum before and after
Credit: Jaime Milan

What do you guys think? I personally can tell a difference. The blooms and leaves look perkier and more hydrated after dipping the stem in alum! While the jury is still out, I’m calling this hack a win.

If you do want to try alum on your flowers, don’t use alum powder for cooking after dipping your stems in it. Fertilizers and/or bacteria from your plant could cause cross-contamination if used in food. Happy clipping!

Jaime Milan is EatingWell’s digital editor for all things newsy and trending. She’s always on the hunt for the latest and greatest things to share with EatingWell’s readers. In her spare time, you can find her experimenting in the kitchen, tackling home projects with her husband or taking pics of her very photogenic American Eskimo Dog, Grits. Follow her on Instagram at @jaimemmilan