The Unsung (and Unseen) Heroes of our Green Wall

Longwood’s Green Wall is a truly stunning sight to behold. Our guests snap hundreds of photos of it and reactions of “oohs” and “ahhs” can be overheard every day.

Guests to Longwood aren’t the only ones who love the Green Wall. To insects and mite pests, this visual masterpiece is nothing more than a vertical buffet of juicy, delicious plants just waiting to be feasted upon. It’s not a matter of “if” the Green Wall will get pests; it’s a matter of “when.” The densely planted foliage provides lots of cover for mealy bugs to hide and many of the plant varieties are known hosts for spider mites.

Longwood’s Integrated Pest Management (IPM) staff battles these pests with a non-chemical approach called biological control. Biocontrol, as it’s known for short, has been part of Longwood’s IPM program since the mid-90s and is the use of one live organism to combat another. We do this by purchasing beneficial insects and mites from commercial insectaries and then releasing them according to a schedule. At 4,200 square feet in surface area, our Green Wall, the largest in North America, is the perfect place to use this method large-scale. Since last spring, we have been releasing several biocontrol agents on the Green Wall.

A close up of some of the plants on Longwood’s Green Wall

To control aphids, we release tiny wasps called Aphidius ervi. No larger than gnats, these wasps sting individual aphids and lay an egg in each one. As the egg hatches and develops into an adult wasp, the aphid dies. Although a few Aphidius ervi wasps can destroy an aphid population, they pose no danger to humans as they are much too small to sting us.

Released in tiny bags called sachets, Amblyseius californicus, a type of mite, prey on spider mites. Each sachet contains approximately 2,000 mites and serves as a breeding system. Because they can go dormant and survive in the absence of prey, Amblyseius californicus work very well as a form of biocontrol. On the Green Wall, we do our best to hide the sachets, but if you have a sharp eye you can find them.

Another predatory mite we use is Amblyseius swirskii. This mite eats whiteflies and thrips. Like its cousin Amblyseius californicus, Amblyseius swirskii comes in breeding sachets that are hung among the plants in the Green Wall. However, it isn’t as hardy as Amblyseius californicus and needs a constant source of prey to survive. Encarsia formosa and Eretmocerus eremicus are both parasites that kill whiteflies. Like Aphidius ervi, they are tiny wasps that sting their prey. These two species are mixed in a 50-50 ratio and deployed on small cards that we hide among the plants.

To control thrips, we use the minute pirate bug, Orius spp. Orius are very small—only a few millimeters in length. We distribute them as adult insects which will not only feed, but also mate and lay eggs. In addition to being excellent thrip predators, Orius also hunt aphids and spider mites. Best of all, they survive on plant pollen in the absence of prey, ensuring that we will always have a population on the Green Wall.

Cryptolaemus montrouzieri is a mealybug destroyer. These lady beetles are completely black except for a spot of red near their heads. Released as adults by the thousands on the Green Wall, Cryptolaemus montrouzieri produce larvae that closely resemble mealybugs. We want our Cryptolaemus montrouzieri to lay eggs because larvae are even hungrier than adults and can trick mealybugs into being eaten.

So far, we’ve been very pleased with the results of biocontrol on the Green Wall. Although we do occasionally find a few bad guys, our biocontrol agents are keeping pests at levels well below what we can tolerate.

A view of the fountain at the Green Wall

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Purr-fect Partners

Today was the annual health check-up day for the cats at Longwood.

Eleven cats patrol Longwood Gardens, from the Nursery to the Peirce-du Pont house. Each cat has an assigned area of the garden and a human caretaker. The responsibilities these felines take on are varied. Their primary job is on the Rodent Control Task Force, but they also work as greeters, work supervisors and highly skilled catmint pruners.  They work in exchange for food, shelter and a health care plan.  Every March Dr. Tonya Nowell of Keystone Animal Hospital in Oxford PA makes the trip out to Longwood to administer an occupational health exam and give booster vaccinations.  This year, thanks to the cooperation of all the human caretakers, and most of the cats, the good doctor, and her assistant Amy, checked out all 11 cats in record time.

Noel waits patiently for her check-up

Vincenzo almost succeeded in evading capture, but Dr. Nowell got down low, with cat treats in her hand and speaking soft and sweet like the cat whisperer, she won Vincenzo’s trust; just before breaking it with a handful of vaccination shots. Nearly all the cats received a clean bill of health, though Smokey and Noel showed signs which require further monitoring. The tissue inside Smokey’s eyelids too pale which the doctor said may indicate a chronic condition. Noel has lost some weight and did not enjoy having her abdomen squeezed by the veterinarian (I wouldn’t either). Some cats are a little afraid of the doctor and require corralling, others like Belin purr through the whole affair.

Get to know Longwood’s Rodent Control Task Force:

Belin's favorite chair

Belin

guardian of the historic Peirce-du Pont house, has a name with historic origins; “Belin” (pronounced BEE-lin) is Ms. Alice du Pont’s maiden name. Belin is probably Longwood’s most famous feline; however he has very humble origins. Rescued from a dumpster at The Terrace Restaurant in 2004, at first he was covered with grease and very afraid of people. Nowadays, Belin can’t get enough human attention and he works closely with Longwood’s guest service representatives, as an ambassador to the thousands who visit the House each year. One of his favorite spots is curled up on a chair in the Peirce-du Pont house conservatory.

Rebar contemplates the mulch

Rebar

the tiny black and white Major Domo of the Hillside Garden, is one of Longwood’s most senior felines. She grudgingly shares this space with other cats that need to be held temporarily in the two “Cat Hospitals”. She is named after the steel metal rods often used as plant stakes, a material which she is every bit as tough as! One of Rebar’s favorite games if playing chicken with the garden vehicles every morning as someone arrives to get her breakfast.

Kousa hard at work on the skid-loader

Kousa

looks a bit like a cross between a cat and a polar bear. She is large and white, and hibernates for most of the colder months inside the Carriage Shed on the eastern side of the garden. She is also stone-deaf, which means she isn’t perturbed by all the noisy machinery in her area, where mulch and soil and debris are routinely being dropped off and picked up.

Noel takes a seat in the conservatory while Smokey enjoys the pumpkin display

Smokey and Noel

are the lucky pair who inhabit the Idea Garden shop on the western side of the garden. Their home just happens to be the shop closest to the largest catnip patch on the property, which may explain their happy and affectionate personalities. Given a choice between a person and food, Smokey would choose the person every time. Noel is a foul weather friend; the colder it gets the more she wants to be on your lap. In the winter she sometimes sneaks into the conservatory where I have spotted her curled up happily next to seated guests.

Missy on patrol

Missy

lives with the arborists at Webb Barn east of the garden. She is a little calico with a license to kill. She takes her rodent catching duties far more seriously than most of Longwood’s other cats, often leaving gifts for her caretaker. No prey is too fast or cunning for Missy. If only she were a bit bigger, she might play a role in deer population control. She keeps mostly to herself and gets her work done.

Smitty and Jojo share a box

Smitty and Jojo are the sisters who patrol the nursery. Jojo is black with a white bib, stomach and toes. Smitty is nearly all black, with white only on her stomach. They show occasional sisterly affection toward one another, stopping to bump noses now and then, but usually stick to their own turf.  Jojo spends much of her time in the area around the barns and tenant houses.  Smitty loves people and hangs out in and around the nursery greenhouses.

Spooky says "BOO!"

Spooky and Vincenzo

share a cozy little heated hut nearby the Terrace Restaurant. Their close friendship goes to show that opposites really do attract. Their appearances and personalities could not be more different. Vincenzo’s long grey fur sports the just-rolled-out-of-bed look; while Spooky’s sleek black coat can outshine any other cat in the garden. As for their personalities, “Spooky” is anything but Spooky; this charming Terrace Restaurant greeter has won the hearts of many guests.  Vincenzo-more appropriately “VincenzA”- was originally discovered behind the Italian Water Garden and was named in part for her tough demeanor, but she is in actuality super shy. When Spooky occasionally goes exploring on his own, Vincenzo cries and cries for her missing friend.

Iggy looking for trouble or maybe just food...

Iggy

usually hangs out around Flower Garden Walk. He has a black coat with a white face, chest and boots; but don’t let the tuxedo fool you, with a neurotic personality and a gift for getting into trouble, he more than lives up to his namesake–Iggy Pop. If he wants your attention he’s not afraid to open his mouth and ask for it. His high-jinx include getting himself locked in a woman’s bathroom, and caught in a have-a-heart trap set for capturing skunks.

Dr. Nowell (left) Kousa (center) Amy (right)

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