The easiest way to get ants off peonies is a quick dunk in cold water. Hold the bloom upside down, swirl it in a bucket or sink of cool water, and the ants wash right off. But before you go to war with the ants on your outdoor plants, it’s worth knowing that they’re not hurting your peonies at all, and trying to eliminate them from the garden is unnecessary.
Why Ants Are on Your Peonies
Peony buds produce a sweet, sticky nectar on the outside of their flower buds through small glands called extrafloral nectaries. Ants feed on this nectar, and in exchange, they act as a kind of security patrol. They aggressively chase off caterpillars, aphids, and other insects that would actually damage the plant. This is a textbook example of biological mutualism: the ants get food, the peony gets protection.
One persistent myth claims that peonies need ants to open their buds. They don’t. Peonies bloom perfectly fine without a single ant present. The ants are there for the sugar, not to pry petals apart.
Leave Outdoor Peonies Alone
If the ants are on peonies growing in your garden and you’re not planning to cut them, there’s genuinely no reason to intervene. The ants aren’t damaging the flowers, the leaves, or the roots. Spraying pesticides or setting ant traps around your peonies removes a free pest-control service the plant is actively paying for with nectar. Illinois Extension specifically advises against treating ants on outdoor peonies, noting that the impulse to control them comes from our discomfort with ants in human spaces, not from any threat they pose in the garden.
Once the buds open fully and the nectar dries up, the ants leave on their own. The relationship is temporary and self-limiting.
Removing Ants From Cut Peonies
When you want peonies in a vase indoors, the ants obviously need to go. The method depends on when you cut them.
Cut at the Marshmallow Stage
The cleanest approach is to cut your peony stems when the buds are at what growers call the “marshmallow stage.” At this point, the buds are still closed but showing some color, and they feel soft and squishy when you gently squeeze them between your finger and thumb, like a marshmallow. Fewer ants have gathered at this stage compared to a fully open bloom, and the tight bud shape makes rinsing them off simple. Just dip the buds in cool water, swirl gently, and any ants wash away. The flowers will continue opening beautifully in your vase.
For Fully Opened Blooms
If you’re cutting peonies that have already opened, hold the flower upside down and give it a few gentle shakes. This knocks off most of the ants. For any that cling on between the petals, fill a sink or bucket with cold water, submerge the bloom upside down, and swirl it around for 15 to 20 minutes. The cold water drives the ants out of the layered petals where they like to hide. Lift the flowers out, let them air dry on the counter for a bit, then arrange them in your vase.
Some people add ice to the water to make it extra cold, which seems to speed up the process. Either way, this is purely mechanical removal. No soap, no insecticide, no vinegar needed.
What If Something Is Actually Damaging Your Peonies?
If your peony buds aren’t opening, or your leaves look twisted and deformed, the problem isn’t ants. It’s worth checking for actual pests that do cause damage.
- Aphids are small, soft-bodied insects that cluster on new growth and the undersides of leaves. They suck plant sap, causing leaves to curl and twist. A telltale sign is sooty mold, a black dusty-looking fungus that grows on the sticky waste aphids leave behind.
- Thrips are tiny, elongated insects (less than an eighth of an inch long) that can be yellow, brown, or black. They feed on buds and flowers, causing buds to fail to open or producing streaked, discolored blooms. Infested leaves look dried out with a silvery, scarred appearance. You can check for thrips by shaking a suspect flower over a white piece of paper and watching for tiny moving specks.
A healthy plant covered in ants is a plant that’s working as designed. Before reaching for any spray, look for actual damage first. If the leaves are green, the stems are strong, and the buds are developing normally, the insects on your peonies are the helpful kind.