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Watershed Staff Grow Host Plants For Hungry Caterpillars

June 10th, 2022

Watershed Educator Vicky Allen has created both a plant nursery and infirmary in the courtyard of the Watershed Center to ensure there will be a vibrant supply of host and nectar sources for critters inside of the Kate Gorrie Butterfly House.

She and other Watershed staff have been prepping the grounds and food sources for the butterflies from tomorrow’s opening through the October closure of the seasonal butterfly house.  Tours will be available on upcoming Thursday mornings in July with Watershed staff and interns who will explain the wonders of the butterfly world. The butterfly house is free and open to the public from dawn to dusk during the season.

A plentiful supply of butterflies inside the enclosure depends on the availability of native insects in the fields of the 950-acre Watershed Reserve. Staff does not purchase or transplant butterflies from elsewhere.

This year, with the supply chain issues snarling the available inventory of host plants, Vicky decided to take matters into her own hands. She has grown about 40 plants in the Watershed’s courtyard and twice that number in her garden in Edison, NJ.


Starting from seed, she has grown swamp milkweed, lobelia and butterfly weed. It is important that the flowers will bloom at different times of the summer, offering nectar as a food source for the adults inside of the butterfly house.


“We decided to do this plant nursery because we had a hard time finding new plants. We are growing our own to increase our host food supply,” she said. “I love gardening and I saw a problem, and so I am trying to find a workable solution,”


“People come to see the butterflies, and this has been an unusual year for the butterfly house,” Vicky added. “This year’s adult population isn’t as readily available to be caught in our fields and brought inside the Kate Gorrie Butterfly House.”


Monarchs and Black swallowtails are the stars of the butterfly house because they are so big and flashy. Each species has specific host plants where they lay their eggs, giving caterpillars easy access to nourishment.


Black swallowtails use parsley, dill, fennel, and golden alexander – all members of the carrot family – and Queen Anne’s Lace as host plants. Monarchs only use milkweed family members as host plants. So, it’s vital to have a steady supply of both readily on hand. 


“As the caterpillars grow, they use these host plants to do all of their growing and eating,” she said.


When those host plants are stressed, she will bring them back to the courtyard to recover in the infirmary. Her grown plants will go into the butterfly house to ensure there are plentiful sources of food for the hungry caterpillars.


Suppose Vicky can’t keep up with the voracious appetites of the additional plants? In that case, Watershed Educator Alison Novobilsky will move any excess caterpillars from the butterfly house into the courtyard. There, they will be placed inside two boxes, which are screened to protect against predators such as birds, praying mantis, and wasps.


The caterpillars will feed off of host plant stalks immersed in water vases. They will stay in the screen boxes through their life stages of caterpillar and chrysalis until they eclose, or emerge as butterflies.


“It takes a couple of hours for a butterfly to fully dry and inflate its wings,” Vicky said. “Depending on the population inside the butterfly house, we will move them in there or let them fly free.”


The butterfly house displays many species with poetic names in any given year, including the Silvery Blue, Great Spangled Fritillary, Little Wood Satyr, Pearl Crescents, and Common Wood Nymphs.


Families at this weekend’s seasonal opening of the butterfly house accompanied Alison with nets to see if they could add to the critters inside the enclosure. 

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