The Secret Ingredient That Will Keep Hydrangeas Flourishing

Hydrangeas not only smell amazing but also look gorgeous in a vase on the dining room table. Because of this, many people have had the experience of carefully cutting a group of hydrangeas from the garden and bringing them inside only to find out one important fact about these colorful flower balls — they are quite hard to keep alive. Hydrangeas are very thirsty flowers and can wilt extremely quickly (even overnight) if not given enough water or if they are unable to drink the water they are in. Luckily, there's a fast and easy way to prevent this from happening and all you need is an ingredient easily found in the store: alum powder.


Alum powder, scientifically known as potassium aluminum sulfate, is a common ingredient in homemade pickles and helps to keep the pickled vegetables tasting crunchy and fresh. Because it is used in food preparation, this powder can easily be found in the spice aisle of your grocery store or online. It is also often sold by bouquet design companies because it is so good at keeping flowers fresh — especially those from perennial shrubs like lilacs, roses, and hydrangeas. Alum does this by allowing the flowers to soak up more water than they normally would, keeping them strong and colorful instead of sad and floppy.

How to use alum to make your hydrangeas last

How you use alum powder to help your hydrangeas flourish may be slightly surprising because you can't just simply add the powder to the water like you would with flower food. Instead, as outlined by a florist on Reddit, you should cut the stems at an angle to provide more surface area for the flower to drink from and then you can dip the cut side of the stems in the alum powder before placing the flowers in a water-filled vase. 


The same Redditor also recommended soaking the entire flower — stem and all — in water before cutting and dipping it in alum. This works especially well to freshen up store-bought hydrangeas because hydrangeas can also drink water through their flowers and petals as well as through their cut stems. So, soaking the whole flowers in a bath of cool water once you get inside from the garden or back from the store is a great way to liven them up before cutting them, dipping them in alum, and arranging them in a vase.

Other ways to keep hydrangeas fresh

There are also other ways you can help your hydrangeas stay fresher for longer that work well in combination with alum powder. First, because these flowers can drink through their petals and leaves, you can mist the flowers with a spray bottle filled with water a few times a day to help them stay hydrated. You can also cover your bouquet with a plastic bag at night to prevent too much water from evaporating from the petals.


Furthermore, it is important to change the water in your vase and replace it with fresh water. This is because cloudy water that is filled with microbes and bacteria can start damaging the plants and cause them to wilt. It is recommended that you change the water in a hydrangea vase every three to four days. When you do, you can also recut the stems of your hydrangeas and dip them in alum powder again to keep them going even longer. Using this method, you should be able to get your hydrangeas to last two to three weeks in the vase instead of just a few days.