Interview with Kwesi Joseph, Urban Gardens Specialist with Cornell Cooperative Extension’s Harvest New York

by Anna Speck

Kwesi Joseph is a Master Composter working with the Cornell Cooperative Extension’s (CCE) Harvest New York. The CCE works with communities and families to help them continue to succeed in a climate that is rapidly changing. His expertise not only in composting but also in soil remediation and integrated pest management have made him an invaluable asset to community gardens across New York City 

After learning about natural gardening techniques, he has become an advocate for integrated pest management, meaning that pests are controlled not with pesticides but with strategically selected plants. Also, as an early advocate for ending the use of synthetic fertilizers that deplete the soil and replacing them with rock dust to remineralize and promote healthy soil, he is working with Harvest NY and NYC Parks GreenThumb to incorporate rock dust into the compost and soil used in community gardens throughout the city. 


Food Policy Center: Thank you for taking the time for this interview! To start, how has planting your own personal garden influenced your work with community gardeners through the Cornell Cooperative Extension’s Harvest New York?

Kwesi Joseph: Having been a gardener for ten years prior to joining the Cornell Cooperative Extension (CCE), I developed battle-tested methodologies for gardening through which I gained a ton of respect for the intelligence of squirrels, birds, cats, insects, and trees. My tactics were honed by countless trials and seemingly infinite errors. The few successes I had became my grizzled approach to gardening. In the movie Jurassic Park, Dr. Ian Malcom says, “Life finds a way.” I’ve experienced that firsthand, nature is resilient.

I started gardening in 2011 in the shadow of a huge tree. My favorite vegetables to grow were Holland White cucumbers, ground cherries, purslane (because it was high in omega-3s), orach (a leaf vegetable), red amaranth (similar to orach but grown for its seeds), callaloo, collards, and kale. I would blend the greens to make smoothies in the morning. The Bountiful Gardens seed catalog was my favorite, because it had lots of growing information and a wide assortment of seeds that I have not been able to find in any other catalog.

In 2015, I was certified as a Master Composter through the Brooklyn Botanic Garden. Afterwards, I became the Compost Manager at the Hattie Carthan Community Garden, where I remained until  2021, and a member of the Hattie Carthan Food Justice Leadership Connective. In addition to what I learned from Farmer Yon, I did lots of reading about gardening, learning about things like rock dust, biochar, and nematodes. It is these experiences that have molded me into who I am as a gardener.

FPC: April is Earth Month. What do you think NYC can do better in terms of urban agriculture and mitigating the effects of climate change? Can you speak to that in the context of gardeners and consumers?

KJ: NYC needs more active green spaces. Community gardens provide several benefits to all members of society. NYC can also make gardening a mandatory part of the school curriculum from kindergarten to 12th grade. This will teach the children, the most vulnerable in society, the importance of eating vegetables and how to grow them. Children will also learn which foods to avoid.

Gardening is science, technology, engineering, arts, and mathematics (STEAM) with an outdoor component. I taught a simplified version of the periodic table of elements to third graders (eight year olds) by first using gardening and composting. Every school needs a dedicated gardening teacher. A regular teacher with the additional burden of running a gardening program will quickly burn out and quit.

Community gardens also need dedicated staff. Being a gardener in NYC is almost as exclusive as being a White House intern in Washington D.C. Some of the gardeners I’ve known were being supported by their parents or were using public services to make ends meet. Most garden jobs are low-paying and seasonal. Gardeners do more than grow hyper-local, nutrient-dense vegetables, and they need to be paid a living wage.

Mardelle Shepley, a professor, and Executive Director of the Cornell Institute for Healthy Futures (CHIF) told me about the research she has done indicating that having more green spaces in urban environments will decrease crime (Shepley et. al., 2019 and Sadatsafavi et. al., 2022). Residents of large cities are often isolated and lonely, especially seniors. Gardens are a communal oasis in a concrete desert, and their benefits far outweigh their costs or carbon footprint. They are preventative and restorative.

Think about what ails our society: depression, anxiety, unresolved trauma, isolation, obesity, and the three horsemen of cardiovascular disease – diabetes, hypertension, and high cholesterol. All of these maladies can be addressed with adequately staffed community gardens providing a wide variety of services beneficial to all ages. Gardens also slow the movement of rainwater runoff, increasing the lag time before that water reaches the sewers in flood-prone areas*. Gardens, like other green spaces, help regulate temperature, provide shade and decrease the heat island effect that makes urban areas significantly warmer than surrounding rural areas, because plants reflect heat from the sun back into space more efficiently than cement does. The insolation (incoming solar radiation from the sun) is reflected into space.

*This reduces flooding because there is more ground absorption of water, slowing the impact of high volumes of rainwater on the sewage system.

FPC: Much of your expertise is focused on or related to soil health (please correct me if I’m wrong). Can you speak to the importance of soil health as it relates to climate change?

KJ: One of the keys to healthy soil is the percentage of organic matter it contains. Organic matter is multifaceted: it acts as a buffer in the soil by controlling pH levels, it holds on to the nutrients/chemical elements in the soil. More organic matter decreases the leaching of the nutrients from the soil when it rains.

According to the United States Department of Agriculture (USDA), if you increase the organic matter in the soil in one acre of land, which is an area slightly smaller than a football field, that land can hold up to an additional 25,000 gallons of water. This ability to retain water is critical to abating the effects of climate change on farms. With aquifers being drained faster than they are being recharged, the pore spaces in those rocks are compressed, decreasing the permeability or water-holding capacity of the rocks.

As the atmosphere continues to warm, it will be able to store more water vapor. This means that evapotranspiration – evaporation (water vapor being removed from the land into the air) and transpiration (water vapor being removed from plants into the air) will increase, so farms will need more water to grow the same quantity of food. The USDA recommends that farms have five percent organic matter in their soil, but farms in the USA typically have less than that.

In nature, healthy soil is usually not barren, but after the growing season on most farms, the soil is left bare to face a depleting, compacting, and hardening winter. Weeds take root in these harsh environments, and tons of expensive fertilizer are needed to resuscitate the soil the following spring. By growing cover crops, farmers would be achieving three major benefits for their soil.

The cover crops would keep the topsoil in place during the winter – topsoil erosion is a major global issue. Cover crops, like most plants, share some of their photosynthesized food with the life in the soil via the plant roots. This food is called root exudates. Simply put, plants take care of the life in the soil by feeding it. Then, in the spring, when the cover crops are turned under or buried, they quickly decompose, adding fertilizer (especially nitrogen) and organic matter to the soil. In short, cover crops are a form of green manure and are critical to soil health, which, in turn, is critical to fighting climate change.

However, healthy soil does more than assist in the mitigation of climate change. It can change human health. My favorite formula is healthy soil = healthy plants = healthy people. Soil is life. Soil is alive. Soil is more than just a growing medium.

FPC: You’ve done a lot of work using rock dust for soil remediation. Can you explain this process and how it can help to sequester carbon?

KJ: Excluding carbon, hydrogen, and oxygen, plants need about 16 chemical elements to grow. However, half of them are trace elements. The macronutrients are nitrogen, phosphorus, and potassium. The secondary nutrients are calcium, magnesium, and sulfur. The trace or micronutrients are boron, chlorine, copper, iron, manganese, molybdenum and zinc. Copper and zinc are heavy metals and toxic in high quantities.

These trace elements are key to plant health and nutrient density, and they need to be replaced in depleted soils. By adding powdered basaltic rock to the soil, the trace elements can be replenished. Basalt is a dark, dense rock that is high in trace elements, especially iron. But plants can’t extract the nutrients from the rocks by themselves. The life in the soil must act upon the rock to make them biologically available for plants. So the plants and the soil life have a symbiotic relationship – they help each other out.

Crushing the basalt rock into a powder will increase the surface area, making it easier for the life in the soil to act upon the rock. But basaltic rock dust doesn’t make a bigger plant or vegetable; it helps the plants become more disease- and pest-resistant, which will increase yield, and the plants also become more nutrient dense, which has a direct effect on human health.

The process of adding basaltic rock to the soil also slowly removes carbon, a greenhouse gas, from the atmosphere via a process called carbon sequestration or enhanced weathering. Silicon (the most abundant element in basalt) binds with carbon molecules locking them into a stable form that can be stored in the earth for a long time. I must emphasize that the primary way to decrease greenhouse gasses in the atmosphere is to reduce the quantity being emitted into the atmosphere, so this is a beneficial byproduct of using rock dust to increase the nutrient density of plants.

FPC: How does integrated pest management work? Do you think it is ultimately easier to implement, as well as being more sustainable and environmentally friendly, than using synthetic pesticides? 

KJ: There are insects that eat the insects that eat our crops. These are called beneficial insects. An easy way to get beneficial insects into a garden or onto a farm is to grow flowers they like to feed on. Also, you can create a habitat where the insects are able to feed, hide, and reproduce, such as insectaries in gardens or beetle banks on farms.

Pesticides are nondiscriminatory; when applied to an area, they will kill all insects, and because the tiny beneficial ones are the least resistant, pesticides generally kill them all. We can drastically reduce the use of pesticides by practicing integrated pest management (IPM). By giving up five percent of growing space to plants that nurture beneficial insects, a farmer or gardener can recoup that loss of space by the increase in yield due to the decrease in pests destroying crops.

My favorite plants to grow to attract parasitoid wasps and other tiny pest killers are plants with tiny flowers, including sweet alyssum, buckwheat, and yarrow (a perennial). The tall plants I use to attract pest-eaters (which I place in the northern part of the garden to prevent them from blocking the sun and creating shadows on the vegetables) are sunflowers and sorghum. I also use cosmos, borage, bachelors buttons, and calendula to attract pest-eating beneficial insects.

These plants attract my army of killer insects. Some of them are flies (yes there are beneficial files), parasitoid wasps, lady bugs, ground beetles and soldier beetles. Ground beetles eat the grubs of the pests overwintering in the soil, and they also eat weed seeds. I read an abstract for a paper that says beetles can reduce weeds by 20 percent. Spiders are ninjas. A healthy garden has lots of spiders and earthworms. But not all plants entice insects; some, such as marigolds, onions, and garlic, actually repel them. If you want to grow brassicas (collards, kale, cabbage, etc.) plant lots of alliums (onions, garlic, scallions, shallots, leeks, and chives) around them to keep away pests, especially the white cabbage moth.

The ultimate form of IPM with which I experimented were nematodes. I think of them as the nanobots of my army. Nematodes are microscopic worms that naturally exist in the soil. Buying five million will saturate the soil with these worms who hunt for grubs and pests. Nematodes find the grubs in the soil by the heat and carbon dioxide they emit, and because they are so small, they crawl into any open orifice and release a bacterium that kills the grubs. I used nematodes to get rid of the cucumber beetles that wiped out my cucumber plants in 2013. In the future, I would love to incorporate bats into my IPM strategy, since they eat a ton of mosquitoes.

FPC: What policy changes, in terms of zoning, ag regulations, and/or budgeting, would you like to see implemented at the city level to promote sustainable and accessible urban agriculture in New York?

KJ: Urban gardens need to be preserved in NYC. The founders of these gardens are now elderly; they have either relocated or passed away. The remaining members need dedicated help, not just volunteers. Most of the gardeners I meet are older and more established financially; they typically own their homes. The younger folks who are interested in gardening have to work multiple jobs to be able to afford their rent. They don’t have the time to dedicate to gardening.

Although composting is promoted, it may not be feasible at some community gardens because of rodent density. But cover-cropping is an inexpensive way to add nutrients to the soil. I think community gardens should be encouraged to use cover crops. One of my long-term goals is to get rock dust supplied to community gardens in NYC. To me, it is more important for soil and plant health than compost.

More Details:

One word you would use to describe our food system: Destructive.

Food policy hero: Yonnette Fleming

Your breakfast this morning: Two scrambled eggs from Hattie Carthan’s chickens with mushrooms and some vegetables.

Favorite food: Curry Chicken (not chicken curry), there is a difference.

Favorite last meal on Earth: My wife’s cooking: rice and beans with macaroni salad, potato salad and fried chicken legs.

Favorite food hangout: BKLYN Blend

Food policy social media must follow: Qiana Mickie

Related Articles

Subscribe To Weekly NYC Food Policy Watch Newsletter
Subscribe to our weekly email newsletter today to receive updates on the latest news, reports and event information
No Thanks
Thanks for signing up. You must confirm your email address before we can send you. Please check your email and follow the instructions.
We respect your privacy. Your information is safe and will never be shared.
Don't miss out. Subscribe today.