Brooklyn Bridge Park is a shining example of ecological horticulture at work and its many benefits. To continue our conversation on how it works and practical ways to apply ecological horticulture at home, Rebecca McMackin is back for Part II of this important discussion.
Rebecca is the director of horticulture at Brooklyn Bridge Park, an 85-acre New York City public park built on piers that were originally constructed to accommodate cargo ships. She is also a garden designer and Brooklyn Botanic Garden instructor. She holds master’s degrees in both environmental biology and landscape design. Rebecca encourages inviting biology into the garden rather than trying to keep it out.
If you missed Part I of my conversation with Rebecca, you can listen now. It will help you to better understand ecological horticulture and other topics that we discuss in Part II.
Practice Restraint to Benefit Wildlife
We gardeners create a lot of beautiful spaces, but along the way, we do a lot of not so pretty things to make that happen. We can reduce our negative impacts on the environment and wildlife by adopting organic gardening practices and can have a positive impact by engaging in ecological horticulture.
Disturbing our gardens as little as possible is one simple way we can help beneficial insects and other wildlife to proliferate. Leaving the leaves is another. Both are easy to do and neither require research or education. IPM, or integrated pest management, is a practice that I always encourage — and it doesn’t take much to get the hang of it.
Leaving the leaves where they fall is better for the insects that overwinter in leaf litter and for soil health. Fall leaves provide shelter for a wide variety of beneficial insects, and when they decompose they improve soil health — which is also good for plant health.
IPM is a step-by-step process to control pests with as little intervention as possible. It starts with positively identifying pests and monitoring plants. Action is only taken when necessary, and the least impactful control methods are used first. By proceeding with restraint, gardeners can manage pests while having little to no negative effects on neutral and beneficial insects.
Rebecca says that by increasing our tolerance of pest damage, we give beneficial insects a greater window of opportunity.
“When you look at the way that classical horticulture has treated disease and pests in the past, it is really not okay,” Rebecca says. “We’ve put a lot of poison down on the earth and still continue to do that today. Really, this is an area that we can continue to improve in because especially when you are planting native plants, you absolutely must make sure that they have been grown without systemic insecticides.”
Systemic insecticides are absorbed by plants through the roots. Because native plants attract native insects, systemic insecticides used on native plants will kill native insects, including pollinators.
“We as consumers need to do our due diligence and communicate this to the nurseries where we purchase our plants from and make sure that they understand what our needs are,” Rebecca says. She points out that systemic insecticides are persistent: They cannot be washed off, and they move into the soil and pollen as well.
IPM is about balance, she says. It encourages the predators that keep pests in check. “It’s not about wiping out anybody. It’s about just having the checks and balances in place. There’s waves of infestations, and then the predators move in.”
In traditional horticulture, pesticides are used that wipe out herbivore insects, Rebecca points out. When the herbivores are wiped out, the predators that would have kept the herbivore populations in check no longer have their food source. The natural balance is thrown off.
In a balanced garden, when aphids arrive and prey on our plants, parasitoid wasps or others predator species swoop in and control the aphid population. For example, Rebecca recalls aphids attacking Brooklyn Bridge Park’s catulpa trees. The horticulture team was encouraged to spray the aphids, but they held back. Eventually, two-spotted lady beetles showed up to eat the aphids. Before then, the two-spotted lady beetle hadn’t been seen in New York City in 30 years, Rebecca says.
When gardens function as systems and gardeners allow for death, gardens are adaptable. Plants can’t move like animals can, so to outwit predators they must evolve. They must be pollinated, they must be allowed to breed and they must be allowed to set seed. The fittest plants will succeed, and over time the surviving plants will be a result of the site on which they are growing. “That only happens when you allow these movements and natural processes to take place,” Rebecca says.
At Brooklyn Bridge Park, the horticulture team is not ideologically against death, she says. “Death is how nutrients get cycled. It’s how weak genetics get culled out.”
The team prioritizes the saplings while allowing older, diseased trees to die out.
Why Having Wildlife Habitat in Cities in Critical
The United Nations expects the world population is going to hit 9.7 billion people by 2050. Currently, half of people live in cities, but by 2050 it’s expected to rise to 75 percent.
“We must figure out ways to gracefully incorporate quality wildlife habitat into cities,” Rebecca says. “It is absolutely critical if we want to be able to support wildlife and biodiversity on this planet.”
Critics of Brooklyn Bridge Park’s philosophy say that the park is engineered and fake, Rebecca says. She agrees that the park is “constructed ecology” and says that the No. 1 priority is to protect existing habitat. “But where you have sections that are devoid of quality, wildlife habitat, learning the methods for creating it and incorporating it are super important and are only going to get more important.”
Minimize the Footprint of Spring Cutback
When the Brooklyn Bridge Park horticulture team cuts back plants in spring that require a trim or pruning to be healthy, they do as little as possible. They also time the cutback so that they have as little negative impact on wildlife as possible. They take their cues from birds that use the plants as habitat during spring migration. They don’t want to disturb birds that nest among the plants.
The team also leaves as much of the organic matter on the ground as practical. When cutting the stems of herbaceous perennials, for example, they want to leave the viable seeds on the ground so the birds have access to the food and the plants can self-seed. Stems are cut in 6-inch segments and are allowed to fall on the ground to become the duff layer — the layer of organic matter that is between the litter layer and the topmost soil layer.
“If you leave those sticks really long, it looks messy. But when you chop them small, it kind of looks like mulch, and it looks great,” Rebecca says. She notes that plants want to live in soil that’s been created from their fallen leaves and their desiccated stems. “Their nutrients will become part of the soil and then get reincorporated back up into the plant, and it is how plants build soil,” she says. “It’s literally how we get soil is by these processes.”
If any stems are hollow or they have pith in the center that is at least an eighth-inch thick in diameter, the team will cut the stems high — at least 18 inches — so what remains can provide habitat for stem-nesting bees. Pollinator conservationist and environmental educator Heather Holm calls this “garden stubble.”
Garden stubble can provide habitat for more than just insects. Rebecca recalls redwing blackbirds using swamp milkweed stems to make their nests. It was the first time that species nested in the park. In fact, many birds will select stems for their chemical properties. That stems do certain jobs in the nest, such as keeping away mites or bacteria. And the silks in milkweed seedpods are fantastic nesting material for hummingbirds in spring.
Encouraging American Lady Butterflies
One of Brooklyn Bridge Park’s goals was to attract the American lady butterfly, also known as the American painted lady butterfly. The species’ host plants include pussytoes (Antennaria) and western pearly everlasting (Anaphalis). so the park ordered a bunch from a nursery. Though they were assured that the plants were not treated with systemic pesticides, the staff smartly experimented with the plants in the park’s lab. They found that all of the caterpillars that fed on the plants died. It turns out that the plants had been treated for thrips, and that insecticide also affected butterfly larvae.
“A lot of these plants don’t like to be grown in a nursery setting,” Rebecca says. “These are wild plants, and it is hard for nurseries to figure out how to grow them in ways that don’t harm wildlife. And it’s only through these conversations and these special orders that we can encourage these processes to use and share this knowledge.”
Spring Planting vs. Fall Planting
Planting in spring requires gardeners to baby plants through the heat of summer. But when we plant in fall, we may only have to water plants for a month before winter comes. Fall-planted trees and perennials simply require less of us to survive. The soil is warmer in fall than it is in spring, so the plants have a better opportunity to grow their roots. They then have all winter and spring to get established before the challenge of summer arrives.
Supporting Migrating Monarch Butterflies
Brooklyn Bridge Park is along the migration route that monarch butterflies take to Mexico. The staff encourages both resident monarchs and those that are just migrating through in late September and early October. The staff ensures that the park provides the resources that monarchs need to complete their journey.
“Monarch butterflies along with honeybees are the rare, charismatic microfauna,” Rebecca says. “Insects so rarely get made into stuffed animals or tattoos, but honeybees and monarchs, everyone knows them. They’re like celebrity wildlife.”
Supporting the monarchs that pass through your garden is something everyone can do, Rebecca says. We can plant nectar-rich flowers to provide butterflies with energy for their journey, and we can plant native milkweed that monarch caterpillars eat.
The Brooklyn Bridge Park horticulture team observes monarchs to learn what flowers they prefer, and then plant more of them. Rebecca says the team has found that monarchs’ No. 1 favorite is groundsel bush (Baccharis), and they also love Asters, late boneset (Eupatorium serotinum) and goldenrod (Solidago). The team will add thousands of these plants to the park soon.
At JourneyNorth.org, you can see the migration patterns of monarchs, birds and even whales. You can make your landscape more hospitable for monarchs by reducing turf and planting the nectar-rich plants they need.
It Takes a Team
Rebecca points out that Brooklyn Bridge Park is what it is thanks to the work of many.
“In horticulture, we don’t always value the people who are watering plants and weeding and planting,” she says. “Oftentimes, manual labor is not really prioritized. And I just like to remember how important the human element is to this work, that when people are not happy in their jobs, when they’re not able to take some time to do research that they’re not going to be good at this work. If having an ecologically managed property is something that you are passionate about and you are hiring people to do that work, or if you have an operation and you’re managing people and you want to do this work, the first thing you need to do is make sure that the people you’re working with are passionate and motivated and respected.”
I hope you learned something from my conversation with Rebecca McMackin. If you haven’t listened yet, you can do so now by clicking the Play button on the green bar near the top of this post.
Have you been to Brooklyn Bridge Park or another park that practices ecological horticulture? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
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joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Tomato expert Craig LeHoullier joins me in leading this course on how to grow healthier, productive tomato plants and how to overcome tomato-growing challenges.
Disclosure: Some product links in this guide are affiliate links, which means we get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast were based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Rain Bird, Corona Tools, Milorganite, Soil3, Exmark, Greenhouse Megastore, High Mowing Organic Seeds, Territorial Seed Company, Wild Alaskan Seafood Box and TerraThrive. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.