The secret your florist has been keeping from you.

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If garden flowers competed in a pageant for our hearts, hydrangeas would win the crown for many Southerners. The classic, elegant blooms — whether you prefer blue, pink, purple, or white — are perfect for being cut, displayed, and shared amongst family and friends. Any green-thumbed home gardener also knows that, despite seemingly simple upkeep, hydrangeas can be a bit finicky to care for in order to get the best, plumpest blooms. (That's where our guide to The 8 Best Secrets to Caring for Hydrangeas can help.)

Alum Powder for Cut Hydrangeas
Credit: Getty Images/Sarsmis

However, some might not know that hydrangeas are also trickier than many other flowers when cut and put into a vase. To put it short, they're thirsty. Like, really thirsty. As soon as they run out of water (and they drink fast!) or stop taking it for whatever reason, you're toast. The blooms start to wilt and deflate into a sad blob of once-breathtaking color. So, if you prefer your cut hydrangeas to last more than a couple days, there is a handy little secret that florists and in-the-know hostesses use to ensure those cut blooms drink as much water as possible, and you can get it in the spice aisle at the grocery store. Ever heard of alum powder? 

Frequently used in pickling and canning recipes to maintain crispness of fruits and vegetables, alum powder (also known as potassium aluminum sulfate) happens to be great for encouraging cut flowers to take more water than when left completely alone. How? By dipping the bottom half-inch of the cut stems' ends into the fine white powder before placing into a water-filled vase. As a result, the hydrangeas will draw more water from the vase, and you're left with happy blooms for days. Oh, and did we mention it will only cost you around $4? Shop it here.

Just remember to keep refilling and never let the stems go bare, and you can expect the hydrangeas to last up to two weeks in some cases. Additionally, you can re-cut the stems at a sharp angle every three to four days, re-dip in alum powder, and place into a water-filled vase to help with freshness.

Go forth, and let those big, fat hydrangea blooms flourish for all to see.