Kenya has one of the highest population growth rates in the world. The present population is about 40 million, but it is expected to double in the coming 15 to 20 years. Nairobi, the capital of Kenya, is home to 3 million inhabitants, and it has already started experiencing the damaging effects of population growth, including skyrocketing food prices.

Overdependence on food imported from rural areas has been regarded the main reason for the incredibly-high food prices in Nairobi. Yet, experts believe that the Kenyan urban agricultural sector, if well exploited, could help bring down the costs of food, by cutting down on transportation costs and reduction of post-harvest losses.

A  study by the Mazingira Institute confirmed that 29 percent of the urban Kenyan population is growing crops, while 17 percent are raising animals within the city limits.

However, Dick Foeken and Alice Mwangi, in an earlier study, found out that although “urban farming was carried out by households across all socio-economic strata, poor(er) households tended to be more engaged with urban agriculture.”

Foeken in his book, To subsidise my income,  concluded that the growth of urban agriculture since the late 1970s was a response "to escalating poverty and rising food prices or shortages."

For example, Foeken says that urban poverty in Nairobi in the mid-1970s was negligible: only 2.9% of the households in Nairobi lived below the poverty line.

But that "between the 1980s and 2000s, the situation changed drastically, due to rapid population growth, the on-going economic recession and the effects of structural adjustment policies, such as a reduction of government spending, increased taxation, currency devaluation, and increasing real producer prices for agriculture”.

Foeken says that it was partly as a result the urban poor getting more marginalized that many people turned to urban farming, “to subsidise their income”.

Covering about 700km2, agricultural conditions are  favourable in most areas of Nairobi. But the demand for housing has seen buildings rise up at the expense of agricultural land.

But it is not yet time to give up on the potential of food production in urban areas. Using such techniques as vertical gardens, city dwellers can grow vegetables for domestic consumption.

“Vertical gardens” is the name given to crops grown in synthetic or sisal sacks filled with soil.

Vegetables are planted at the top of the sack and on the sides on which small holes are punctured. A sack with a volume of 0.1 to 0.5 m3 can take 30–40 seedlings of kale (sukuma wiki) or spinach. The most favourable crops for vertical gardens are are leafy vegetables because they keep on growing even after the leaves have been plucked. 

The only problem with sack gardens is that they tend to be bulky, especially for people living in cities, most of whom stay in apartments. However, even with  limited space, one can still plant spices in window boxes and other small containers-often known as hanging/swinging gardens.

Harun, a carpenter along Ngong Road, makes beautiful window boxes from wood and metal, at a cost of Sh1,200 a piece. While he admits that his boxes are mainly bought by people interested in planting ornamental plants, he says they can be productively used to grow food crops.