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Our Summer with the Yellowjackets

Updated: Feb 10

And Other Nursery News

Many people have negative associations with wasps. Understandable, considering that social, hive-building members of the wasp family, Vespidae, like Bald-faced Hornets and Yellow Jackets, pack a powerful sting and use it against anything they perceive as threatening their hive and all the helpless (and protein-packed) larvae within. So how and why did my husband and I spend a whole summer working in the greenhouse just a couple of feet from an active Yellowjacket nest?

Well... we were busy. The situation just sort of evolved. There are always hornets and wasps in the greenhouse. We are a pesticide-free native plant nursery. One of the techniques we use to harden our plants is to open the sides and ends of the greenhouse, letting in the winds to help build strong stems and teach the plants how to regulate their moisture levels. Consequently, the greenhouse teems with life all summer long. We have butterflies laying eggs on milkweed seedlings, caterpillars munching away, aphids, slugs, beetles scurrying around... and after them come a full-scale army of predators.

My favorite predators are probably the giant toads. They come out at night and stand in the open doors like great fat sentinels, waiting for bugs to wander by. The toads spend the day sleeping in some pot and make startling movements or even squeaks when I accidentally water them with cold groundwater. But, they are by no means the only predator to help us with pest control. The garter snakes are also quite startling to water, but they are mostly there to eat the mice that eat the bugs (and the plants). More directly effective against the insects are our legions of spiders: skittering wolf spiders, jumping spiders that look you in the eye like they want to discuss life, crab spiders that try hard (and often succeed) to look like flowers, fishing spiders as big as your hand, and many many others.

Then there are the birds: this year I watched a pair of fly catchers come in at dawn every day to pluck the insects trapped from yesterday on the inside of the plastic. I also watched with much trepidation and anxiety as they led their July fledglings in to teach them the same trick. The fledglings flew in just fine, but it took them a couple of stressful days to learn how to slip out the louvers in the greenhouse peaks (apparently they don't use doors and windows, which were wide open). All the while they complained and called desperately to their parents and I anxiously stressed about them getting too hot or getting abandoned. It turned out that the parents knew what they were doing. My efforts to "save" the fledglings by trying to catch them with a butterfly net only served to stress everyone out even more. The parents occasionally hopped back in, had a calm discussion with the fledglings about (I assume) the usefulness of greenhouse louvers, and hopped back out. Eventually, the fledglings figured it out.

But back to wasps... Wasps are a major component of our predator army. In case you didn't know, many (most?) wasps, especially the social wasps that make big nests full of young, are predators. They hunt insects, paralyze them with a sting, and bring them, or at least the meaty part, back to the nest to feed the larvae. Solitary predatory wasps tend to paralyze their prey and bring it back to the nest chamber - burying it alive with the eggs. Wasps, the solitary wasps at least, tend to specialize - one will hunt certain types of spiders, one will go after a type of caterpillar, and so on. There are also thousands of parasitic wasps that lay their eggs on the eggs or larvae of other insects. In fact, with over 4,000 species of wasp in the United States alone, there is probably a wasp controlling the population of every single native insect. Creepy, but cool, and very useful in controlling insects, especially in a greenhouse. Many wasps are also pollinators, sipping nectar for an energy boost or because they are males who do not provision nests. They don't collect pollen like bees, but they spread some around as they forage.

a yellowjacket wasp on the ground

...I'll take a moment here to beg forgiveness for any errors in wasp generalizations or terminology - the wasp lineages are complicated and all mixed up with ants and such, their lifestyles are not as well described in common references as social bees, and I am not an insect expert. "Yellowjackets", for example, is a common name for several wasp species. I think the ones in our greenhouse were Eastern Yellowjackets, Vespula maculifrons, but again, I'm not a pro at insect identification. Do feel free to send me an email with all your best wasp facts if I get something wrong...

With all the ecosystem happenings in the greenhouse, we tend to ignore the presence of wasps. They are busy doing their things, and as long as we don't swat them, they are equally content to ignore us. At some point in early summer we did start noticing that the number of yellowjackets seemed higher than usual, and concentrated toward the front of the greenhouse where the workbench and potting table are located. Within a couple of days, the population exploded. We soon discovered they had taken up residence under a stack of dome covers under the potting bench. The potting bench was evacuated while we figured out what to do. We put up a barricade to keep people from forgetting and walking too close to the nest, lest the vibrations of our steps cause a ruckus. I admit, our first impulse was to spray the nest, using the plant-based hornet killer that we normally use for nests on the house. However, since the nest was on plastic landscape cloth and under plastic plant trays, spraying the opening did absolutely nothing, except kill one unlucky sentry wasp. There was no way to get the spray into the paper of the nest without flooding our greenhouse with hornet-killing chemicals. I was loath to fill my pesticide-free greenhouse with that stuff, much less risk my beloved toads and flycatchers either being directly exposed or eating poisoned wasps that were dead or dying. Not to mention the hundreds of Monarch caterpillars on nearby plants, who frequently crawl across the greenhouse floor to find a place to pupate. How long would my floor be toxic? I couldn't risk the shotgun approach. We would have to do something extreme, like get up right next to the nest and spray directly into the tiny hole, or flip the wasp-filled trays over in the middle of the night, run like heck, and then come back later to spray. The layout of the greenhouse prevented easy exit, however, and both ideas seemed like there was a high likelihood of rousing hoards of angry wasps. It was time to call for help.

I moved my employees' work station outside, and began researching pest control sites. Some of them sounded horrid, but I ended up talking quite a bit with a representative from Guardian, Michael Johnson (shout out!). I expected to be scorned when I expressed my concerns about contaminating my greenhouse with pesticides, but he listened, and then he put a great deal of effort into researching alternatives. In the end he came up with a diatomaceous earth method that probably would have been safe for my wildlife, and would have rinsed easily off my plants. However, the whole process took several weeks; summer was nearing its end. And, nothing bad had happened. Let me repeat that, we had now spent six weeks working in a greenhouse containing a nest of yellowjackets, and nothing bad had happened.

Five feet from the active nest, my husband Todd and I continued to use the workbench, water plants, move bales of dirt (gently), construct garden kits, pot up seedlings.... Basically, greenhouse operations were unaffected. The employees much preferred their outdoor work tent to the crowded bench in a 100 degree greenhouse; so much so that we will be using a similar work station this coming year. Todd and I stayed calm and moved slow, and were mindful not to disturb the nest. It did take up some of the space, since we were careful not to store plants or materials too close. But for the most part, operations were unaffected. One thing I did notice is that when things got too frantic in the greenhouse, the yellowjackets would start crashing into me. Not stinging: they would just fly into me and away. It was like a little smack with a bug. I took it as a warning, and would step out of the greenhouse for a bit until things were calm. My yellowjackets never stung me, or anyone else. Coincidentally, I did get stung this summer while hiking on Presque Isle. An insect crashed into me, and it felt the same as when the greenhouse yellowjackets hit, but this one got stuck in my hair. When I reached up to scoop it free, it stung my finger. I looked around and saw an agitated yellowjacket nest at the base of a large tree nearby. I have not read about warning whacks from yellowjackets before, but it seems to me to be what was happening. Far from the crazed attackers described on the internet, the yellowjackets appeared to want to avoid conflict.

Based on the fact that we were only a few weeks from frost, we decided to continue as we were and do nothing about the nest. Although the diatomaceous earth solution seemed pretty benign, there was still a risk to my monarch caterpillars and spiders. Diatomaceous earth is the remains of sea creatures - it is basically dust made out of microscopic shells. It works by abrading the insects and causing them to dry out and die. It is very effective on caterpillars and other soft insects. Even though I could rinse the dust from my plants, the sharp particles would be in the potting soil and on the floor. My monarchs frequently migrated across the floor when looking for spots to pupate. I was also concerned that diatomaceous earth might not kill the hard-bodied adult wasps very quickly, if at all. Killing the larvae within the nest would serve to reduce the population, but I thought there was a good chance the adults would recognize the attack and become less tolerant of humans, making the greenhouse unusable for whatever days or weeks it took to destroy the nest. Since greenhouse operations were minimally affected by leaving the nest, it seemed better to just tolerate the status quo and wait for the coming cold weather to either kill the nest naturally, or at least make it dormant so we could remove it physically.

Layers of wasp nest in an inverted plastic tray
The abandoned nest

I admit I was nervous about this approach. One of the many horror stories you will read on the internet is how yellowjackets get exponentially more aggressive in the fall, as resources dwindle and the breeding activities at the nest change or cease. Fall would also be when we closed up the greenhouse, shutting doors and rolling down the sides, trapping us inside with the nest. But once again, nothing happened. At the first cold snap, we shut the doors and rolled the sides down, leaving the side near the nest cracked open so they could go out and forage. The nest was still active, but activity seemed to be much less. Our activity in the greenhouse was also much less, as fall sales were moderate and fall plants need less water. A few weeks later, after not seeing any movement for a few days, I cautiously flipped the nest over with a snow shovel. It was abandoned. Our summer with the yellowjackets was over, and aside from the one sentry wasp we poisoned early on, no one got hurt on either side.

Now, I know we got lucky. I know a hundred people reading this post are thinking of less lucky encounters they had with ground-nesting wasps. We could have done something to trigger them and wasp stings are awful (deadly for some). I'm certainly not going to judge you if your circumstances cause you to make a different choice. In other years, both my husband and I have been stung doing very innocuous things outside, like walking from house to garage. Did this nest tolerate us because they started from day one in an active greenhouse, so our movements were a normal part of the environment? Were they peaceful in the fall because the greenhouse and yard are rich with resources and there was no stress to the nest? Or are yellowjackets not the monsters portrayed online? I don't know, and I'm certainly not making a blanket recommendation that yellowjacket nests be tolerated in human environments. All I know is that I spent the late summer walking past the nest daily, within a couple of feet, as I collected jewelweed seed from the plants that grow along the edge of our greenhouse. I made sure not to stomp, but the yellowjackets were unperturbed.

This was actually one of two nests we found. The other was a typical ground nest in our front lawn that my husband ran the riding mower over. He fortunately saw the disturbed wasps and avoided making another pass, also avoiding being stung. It is not a high traffic area of our yard. We just didn't mow that corner of the lawn this summer, and again, no one got hurt. Maybe, just maybe, the war on yellowjackets is a little overblown.

a toad about 6 inches away from the door to the yellowjacket nest
Toad Hunting Yellowjackets

Nature includes many roles, and native plant gardening is not just about attracting butterflies. It is about tolerating many things that are considered bad in mainstream gardening - like insects eating your plants, predators like snakes, and maybe, just maybe, tolerating, or even appreciating, wasps.

I plan on writing more on wasps in the future, in the meantime, our summer plant sale schedule is starting to take shape. Check it out Here. If you are interested in plants that will help provide predators (wasps, birds...) with resources in the fall, here is a quick list of plants that teem with fall insect activity:

We are now taking orders for spring of 2024!

Pickup at the greenhouse location will begin when your plants are ready, usually the end of May. As always, orders placed during the May busy season might not be filled until summer as we supply earlier orders and spring plant sales first. However, we have a lot of plants overwintered. Fingers crossed that they survived the early winter freezing rains and that spring sunshine will melt the snow, allowing us to use them to fill spring orders. If we don't get a foot of snow on May first like last year, and it all works, we might be able to fill spring orders in record time. But either way, there is nothing wrong with planting all summer long, even into the fall. Our last order of 2023 was for a November planting!

We are looking forward to the start of the 2024 native plant season and all the life it brings. Thanks for planting native!

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