A little extra juice
It’s that time of year when the tulips bloom, then it snows, then it’s warm and sunny, then it freezes. All very stressful for a recently returned Colorado gardener. I was particularly sad to see my peonies slumped over after a frost last week. Luckily for them, and for me, they seem to have made a full recovery. In fact, they are flourishing and have put out more buds then I’ve ever seen on them.
While I was out examining the buds this weekend (I want flowers!), I noticed some fun entomology happening. On almost every bud there was an ant! I am new to growing peonies so I didn’t know this was thing with them. Being me, however, I am always interested in why insects are where they are and what they are doing. The ants on the buds were clearly feeding. They kept probing at the edges of the sepals on buds.
A little research on this told me that although it used to be thought that the ants were necessary for the peony flowers to open because they forced open the flowers, this is not the case. Ant-less peonies perform just as well. So what are the ants doing their anyway? Peonies produce a type of nectar (sugary water) along the edges of the sepals and flowers. In the picture below you can see the liquid pooling at the base of the bud. The ants are attracted to and eat this liquid. In this video you can see the ant checking all over for the delicious juice.
In return the ants guard the plant from herbivorous insects. This strategy is actually not that uncommon in the insect-plant world. Acacia trees and their guard ants are the classic story. The tree provides housing (in its thorns) and nectar for the ants, and the ants guard the trees from herbivorous animals and other plants. They even attack (MUCH larger) giraffes. National Geographic has an interesting story about this relationship here.
But back to my peonies. Did you notice that the ant is basically as big as the peony bud? That is partially because the buds are still relatively small but also the ants are huge!
These are carpenter ants. Carpenter ants are all in the genus Camponotus. This one might be Camponotus pennsylvanicus, but I haven’t gotten a full list of Colorado carpenter ants so I’m not sure. Carpenter ants live up to their name. They build elaborate homes in decaying and decayed wood. Unlike termites, the ants do not eat the wood. But they do excavate their houses and can cause structural problems in dead trees or untreated wood porches. Like other ants, they have a queen who founds the nest and lays all the eggs that become workers. The workers take care of the queen, the new young, and forage for food. In the spring, an established colony will produce a cohort of new queens. These fly away, mate, and found new colonies. Beside peony juice, they eat other insects they find, honey dew from aphids, other material scavenged from the forage area. People sometimes think of carpenter ants as pests because they can damage wood associated with our homes. Most of the time, however, they are manage to live without much interaction with people. I actually really like seeing them around because it means that the ants haven’t been completely overrun by Argentine ants yet. Argentine ants are another story though and will have to wait for another day.
In summary, the carpenter ants are not hurting the peonies, and there is no need to worry about them. They are just doing what the plant wants them to do.