A green oasis nestles on the barren expanse that is Nairobi's south-east end, somehow managing to blossom between kennels of barking dogs and the exhaust fumes of an auto garage.
Overflowing with colourful vegetables and flowers, the lush patch of garden breaks the grey monotony of concrete and barbed wire, and provides a home to a dozen rabbits, chickens and quail.
Owned and run by the security and courier company Wells Fargo, this garden is the brainchild of the company's operations director, Ms Gai Cullen.
Every new Wells Fargo recruit has to complete six hours of training in the garden. And that's just one way that Ms Cullen -- who doubles as the secretary of the Permaculture Research Institute (PRI) of Kenya -- is trying to spread the gospel of sustainable agriculture.
If "permaculture" doesn't ring a bell, don't be surprised: the Wells Fargo site is one of Kenya's few examples of a permaculture garden.
The term comes from the words "permanent" and "agriculture," describing a concept that combines environmental sustainability with food security.
Simply put, permaculture integrates human habitats into natural landscapes. Its sites use natural processes to provide sustainable production of food, electricity and other human needs.
Ms Elin Lindhagen Duby, an accredited permaculture trainer living in Kisumu, calls it a "whole systems design".
"(In permaculture), you start with observing nature and how ecosystems work, because ecosystems are stable and resilient," she says.
"Ecosystems are cooperative -- the waste of one species feeds another. There is no waste, everything is used."
The best way to understand permaculture is to know what it isn't -- it falls in sharp contrast to monoculture farms, where single crops are planted on large tracts of land.
In that scenario, seeds and fertilizers are purchased from agribusiness firms, crops are harvested and sold, and waste is trucked away.
Instead, permaculture focuses on self-sufficiency. Ultimately, it integrates plants, animals and humans into a closed-loop system where each element -- such as waste disposal or food production -- supports another.
PRI Kenya (www.pri-kenya.org) was founded this year to encourage permaculture in the Horn of Africa. As proof that this concept can work anywhere, Ms Cullen practises permaculture on her property outside Nairobi, which provides a prime example of the techniques used to integrate humans into natural environmental processes.
Each crop cycle is planted using seeds saved from the previous harvest. Permaculture gardens focus on growing species which are indigenous to the region, improving the chances that they will thrive and provide a healthy yield.
A technique called "intercropping" is used, where multiple species are planted together in order to support one another's growth, says Ms Cullen.
"Companion plants" are groups of plants that grow well together in a small space, assisting each other in pollination, pest control, and nutrient uptake.
For example, flowers are planted among vegetables to attract pollinators to the area. Shade-loving plants are grown beneath taller, leafy species to block out the sun.
Garlic and basil keep aphids at bay, so they are companions to plants that are susceptible to pests. For infestations that cannot be controlled by intercropping, natural pesticides made out of soap or ground garlic and chillies do the trick.
Companion planting can also provide fertilizer to the soil -- legumes are natural nitrogen-fixers, meaning they extract nitrogen from the atmosphere and deposit it in the soil.
Therefore, they are well-suited for planting alongside crops which withdraw large amounts of nitrogen from the ground, such as maize.
To replace nutrients that can't be brought into the soil through intercropping, permaculture practitioners enrich the earth with compost and manure, which comes from the plants themselves.
The compost is made from discarded organic materials such as kitchen and garden waste, and the manure comes from animals (such as rabbits or chickens) fed by the site's organic waste.
Aside from producing fertilizer, the animals also provide food through milk, eggs and meat. When released into the garden, chickens aerate soil and hunt for pests.
Ideally, the garden is fed by household wastewater, deposited into a patch of earth encircled by banana trees. Their roots filter out impurities as the water seeps into the rest of the garden. Rain barrels and other catchment systems store water for times of scarcity, and mulch slows down evaporation from the earth.
"Literally it's mulch, mulch, mulch. If anything's drummed into you when you do the permaculture course, that word comes up I don't know how many times every day," says Ms Cullen. "It's to keep the moisture in the soil. Evaporation is the biggest problem we've got in climate change."
At the end of each plant's cycle, the seeds are harvested, and the process begins again.
Facilities allowing, electricity can be provided to the living quarters by solar panels, wind turbines and biogas digesters, which feed on any organic waste from the home and garden (and also produce cooking gas).
Permaculture doesn't have to be applied to large tracts of land in rural areas; it can be used on a variety of scales, depending on the resources that gardeners have available.
About 32 metres square, the Wells Fargo garden can feed a family of four on a daily basis, says its full-time gardener David Amulioto.
"In permaculture, we try as much as possible to use the smallest portion of land... to have a sustainable production of food," he says.
In cramped urban settings, he says, the concept can be applied to growing vegetables like tomatoes or sukuma wiki in planting bags or on rooftops.