The Secret Ingredient Martha Stewart Uses To Keep Cut Hydrangeas Fresh For Weeks

Hydrangeas make a stunning statement in any floral arrangement, so it's a sure bet that when you clip them from the shrub in your garden, you'd like them to last as long as possible. Natural remedies and tips abound, but Martha Stewart has come up with one method that uses an ingredient found in just about any grocery store: alum powder.

Flower aficionados generally try various tips to keep cut flowers alive. The folksy methods are often met with varying degrees of success. Some people swear by adding an aspirin to the water, others add lemon-lime carbonated soda. Still others will plop a coin into the vase, though they rarely explain what denomination the flowers seem to prefer! Many people just use the floral preservative that comes with store-bought bouquets, but when you snip the blossoms from your own bushes, you often don't have those handy little packets.

But whether your hydrangeas are blooming blue or pink, keeping those big, beautiful, showy flowers (especially Hydrangea macrophylla, the big round varietal) looking fresh for days or even weeks can be as easy as opening the cabinet where you store your spices. You need only follow a few simple steps.

How alum powder keeps hydrangeas fresh

Alum powder is a soft, pure white, very finely-grained substance typically used in the pickling process. It's what keeps pickles firm, though the Penn State Extension office says that using alum isn't usually recommended any longer. They don't talk about whether or not alum powder opens up the stems of cut hydrangeas, but a TikTok user who worked for Martha Stewart claims that placing the stems into a jar of alum powder after cutting them will make them last longer because they'll be able to take up more water.

It's important for any cut flowers to be able to "drink" the water in the vase. Most flowers will exude some sap and try to heal the cut, so making a clean, fresh cut is important, as is getting the stem in water as soon as possible. Alum powder's properties help keep the stem open longer thus allowing the flower to keep absorbing water. The water should also be changed regularly, with most florists recommending a change every couple of days. Some will also counsel a fresh cut for the flower's stem, which may necessitate another dip into the alum powder.

Boosting the lifespan of cut hydrangeas

While alum powder dips can keep water flowing freely through your hydrangea stems, you can take other steps to make sure they have the best chance of lasting a long time in a vase. The big blooms are fairly hardy, but with a few tips from Martha Stewart, they can last for weeks.

If you're growing hydrangeas, you already know they won't be ready until the middle of summer. That's when the blossoms will have matured enough to be fully formed and ready to cut. As is the case with most garden activities, from cutting to planting to watering, try to lay low during the middle of the day when the sun is at its peak.

For hydrangeas, it's not just when but where and how to slice the stem. The best spot is above a node (the spot where leaves and buds pop out of a stem) being sure there are two or more sets of leaves above it. Always use sharp, clean instruments to make your cuts.

Once inside, give them another snip, this time above a node and at a steep slant, then split them vertically about an inch or two. Now is the time for a coating of alum powder, after which, trim all excess leaves, which will siphon off the water that the blooms need. Never keep any leaves below the water line; they invite contamination. Keep the water fresh by replacing it every couple of days.