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Growing plants along the vertical axis of a building façade is currently re-emerging as a technique for (re)integration of greening into the urban fabric. This article reports an exploratory study that involved the design, development and evaluation of vertical greening within low-income communities in Lagos, Akure (Nigeria) and Dar es Salaam (Tanzania). We highlight the vertical gardens’ contributions to food production (vegetables). Challenges identified include high maintenance, pests, vandalism, tenure status and socio-cultural misgivings about growing vegetables on walls. It is crucial to evolve policy initiatives and programmes that promote citizen-led, community-based vertical farming within the urban fabric in sub-Sahara Africa.
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Prospects and problems of vertical greening within
low-income urban settings in sub-Sahara Africa
Olumuyiwa Bayode Adegun ,
1,2
Olawale Oreoluwa Olusoga
1
and
Elinorata Celestine Mbuya
3,
*
1
Department of Architecture, Federal University of Technology, Akure, off-Ilesa road, PMB 704 Akure, Nigeria,
2
School of Architecture and Planning, University of the Witwatersrand, 1 Jans Smut, Braamfontein, Wits 2050,
Johannesburg, South Africa and
3
Institute of Human Settlement Studies, Ardhi University, Off University
Road, Dar es Salaam, Tanzania
*Corresponding author. E-mail: angelambuya@gmail.com
Submitted: 31 May 2022; Received (in revised form): 22 July 2022; Accepted: 6 August 2022
Abstract
Growing plants along the vertical axis of a building fac¸ade is currently re-emerging as a technique for (re)integration of
greening into the urban fabric. This article reports an exploratory study that involved the design, development and
evaluation of vertical greening within low-income communities in Lagos, Akure (Nigeria) and Dar es Salaam (Tanzania). We
highlight the vertical gardens’ contributions to food production (vegetables). Challenges identified include high
maintenance, pests, vandalism, tenure status and socio-cultural misgivings about growing vegetables on walls. It is crucial
to evolve policy initiatives and programmes that promote citizen-led, community-based vertical farming within the urban
fabric in sub-Sahara Africa.
Key words: green infrastructure, socio-ecological systems, slum upgrading
Introduction
Growing plants along the building fac¸ade or in the interior,
known as vertical greening system (VGS), is currently re-
emerging as a technique for the (re)integration of greening
into the urban fabric. Vegetation within urban settings miti-
gates urban heat island effects by regulating excessive heat
and moderating the micro-climate (Wang 2016). For instance,
green walls can be up to 10Ccoolerthananexposedwall
(Momtaz 2018). In addition, vertical greening supports food
production through farming upwards rather than outwards
(Beacham et al. 2019). Most available examples and empirical
evidence on vertical greening emanate from studies within
urban settings in developed countries. Only a few studies ad-
dress vertical greening within low-income urban settings in
sub-Sahara Africa.
Vertical gardens were installed in the course of re-blocking
MtshiniWam informal settlement, Cape Town, as socio-
ecological infrastructure and low-space greening technique
(Henning et al. 2012). The vertical farm’s designer, in reflection,
admitted that successful uptake is only possible if the residents
understand and appreciate the gardens. Training, awareness
and relevant resources are needed to enhance uptake (Adegun
2016).
In the same vein, Akinwolemiwa et al. (2018) designed and
built vertical greening prototypes within a low-income neigh-
bourhood of Lagos, Nigeria. After assessing the micro-climate,
food security and livelihood benefits of the gardens, it became
clear that further iterations of the prototypes are needed to
enhance the product-level, market-readiness and social accep-
tance. These experimentations call for further work to fully
understand vertical greening and its peculiarities and
V
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Journal of Urban Ecology, 2022, 1–6
https://doi.org/10.1093/jue/juac016
Short Notes
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potentials, especially the sociological aspects within low-
income, informal settings in Africa cities.
This article focuses on vertical greening in the context of
low-income urban settlements. It is situated within Lagos,
Akure and Dar es Salaam (Dar)—notable cities in sub-Sahara
Africa. Lagos is Nigeria’s commercial capital and contains 20
million people, with estimated 70% of the urban population liv-
ing in low-income areas categorized as slums or informal settle-
ments. Akure is the capital city of Ondo State, Nigeria, with over
600 000 people. Dar is Tanzania’s commercial hub and hosts
over 5.4 million inhabitants. The exploratory study involves
design, implementation and evaluation of vertical greening pro-
totypes conceived as a part of resilience and climate adaptation
strategies.
Developing VGSs for low-income contexts
In designing VGS for the low-income settings, a crowdsourcing
approach was utilised. The definition of crowdsourcing entails
turning to a group of people to obtain certain knowledge and re-
sponse. This approach was taken because we wanted to engage
a larger audience (virtually and in-person), drawing attention to
problems and possibilities within the growing low-income ur-
ban communities in Africa. The lockdowns associated with
COVID-19 pandemic in 2020, further gave room for this ap-
proach and enabled robust engagement through virtual plat-
forms. We worked with a youth-led architecture sustainability
volunteer group known as ‘Pulcher’ to organise a design compe-
tition for university undergraduate students in design-based de-
gree programmes. The competition was part of a research
project focussed on climate adaptation, hosted within the
Department of Architecture, Federal University of Technology,
Akure, Nigeria, and executed in collaboration with Institute of
Human Settlement Studies, Ardhi University, Dar, Tanzania.
The competition’s brief presented the design challenge and
need for a VGS implementable within a real-life low-income,
dense urban environment. After the submission of entries, their
shortlisting and final assessment, six design proposals were se-
lected and awarded prizes. The prize winners had a post-
competition commitment for the implementation of their
designs. Meetings were held with the prize winners to facilitate
the iteration of their entries for implementation. The three final
iterations (now called prototypes) were the recycled
Polyethylene terephthalate (PET) bottle prototype (Figs 1 and 2),
lattice prototype (Fig. 3) and High Density Poly Ethylene (HDPE)
pipe prototypes (Figs 4 and 5).
The prototypes’ design and material selection are based on
the cost, availability of materials and prospects of advancing a
circular economy. A good example is the PET bottle prototype.
In Nigeria, over a billion plastic bags and PET bottles are used
annually (Kehinde et al. 2020), with estimated 75 000 metric
tons of plastic bottles used in Lagos only (Ibukun 2019). With
the poor solid waste management systems, used PET bottles
usually constitute waste problems in drainage channels, con-
tributing to flooding. Using PET bottles for farming can get them
off the streets, drains and landfill. Although relatively available
and cheap, PET vertical greening prototype has some drawback
because the bottle’s small size determines the output in both
quantity and quality.
The second VGS prototype is lattice type (see Fig. 3). This
prototype uses steel angle irons or pipes arranged both verti-
cally and horizontally with the aid of rivets. These angle irons
(5.4 m in length) or pipes (usually 75 mm diameter) are fixed to
the walls through bolts and nuts. Plants will sprout from the
ground and creep around the vertical members. The lattice
structure is most suitable for creeping plants and thus limited.
It also makes additional structural demand on the wall.
The third prototype is made from HDPE pipes (usually
100 mm diameter) placed horizontally, hung on timber planks
slightly sunken into the ground (see Figs 4 and 5). Metal hooks
on the timber carry the half-cut pipes loaded with soil. Holes
drilled in the pipes drain excess water while stoppers glued to
both ends of the pipe keeps soil in place. The prototype has
advantages in terms of ease of construction and possibly
good visual quality. It costs 30 460 naira (US$79) to install a
standard HDPE prototype in Nigeria and equivalent of 34 300
naira (US$89) to install the same in Tanzania (see Table 1).
The HDPE prototype was implemented on residential build-
ings in 7 locations within low-income environments in Akure
and Lagos (Nigeria) and up to 10 locations in Dar (Tanzania).
Figure 1: Design of prototype from recycled PET bottles
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In Nigeria, three indigenous leafy vegetables were planted
(see Fig. 5a). They are jute leaf (Corchorus olitorius) known locally
as ‘ewedu’, Lagos spinach (Celosia argentia) known locally as
‘shoko’ and African spinach (Amaranthus viridis) known locally
as ‘tete’. In Tanzania, four indigenous leafy vegetables were
planted in the HDPE prototype (see Fig. 5b). These are:
Amaranthus spp., known locally as ‘mchicha’; potato leaves
(Ipomoea batatas) known locally as ‘matembele’; pumpkin leaves
(Telfairia occidentalis) known locally as ‘majani ya maboga’ and
legumes belonging to the pea and bean family, locally referred
to as ‘majani ya kunde’.
Food production from the vertical gardens
The vertical green structures developed had a notable contribu-
tion to household vegetable needs in the communities. From a
typical HDPE prototype in Nigeria (see Fig. 5a), up to 1 kg of food
(vegetables) were harvested per cycle. This includes 183 strands
of ‘ewedu’ at average 11 cm long, 106 strands of ‘tete’ at average
17 cm long and 46 strands of ‘shoko’ at average 9 cm long. A cy-
cle of planting can last 6 weeks—from planting to harvesting.
Explanations by two interviewees within the Lagos settle-
ment expatiate on the food (vegetable) contributions. A male in-
terviewee acknowledged that ‘we have plucked from it. Other
people have also come to pluck from it and cooked and they
said it is good ... People come here to see it. They are always
surprised. Even my elder brother came, he has gone to prepare
for it, and I gave him seeds to plant. And he has started harvest-
ing from it’ (Interview 1, Lagos, January 2021). Another explana-
tion by a female resident is that ‘we were shown how to do it
and we’ve started. I was able to do these ones in these contain-
ers. I perforated the bottles so that that air can go into it and the
plant can breadth ... since then, I have been getting vegetables.
Like the ones I plucked today, it’s very green as you can see.
And it is fresh. It nourishes the body more than the one you get
from market which would have become yellowish’ (Interview 2,
Lagos, January 2021). Similar assertion was made by a woman
in Akure who had the prototype on the rear wall of her house
(Interview 3, Akure, July 2020). There is an agreement that the
gardens give food that is fresh.
In Dar, the different vegetables yielded varying quantities.
For ‘mchicha’, two bunches (a bunch here refers to the collec-
tion of vegetables leaves or stem with leaves, which are or can
be simply held by the hand or fastened together; there are no
standards regarding the number of leaves or stems that make
up a bunch) were harvested per cycle lasting 21–25 days. A cycle
would last three rounds, that is, the first two bunches are har-
vested within the first week and the second and third batches
harvested in the second and third weeks, respectively. Several
days after planting, the first growth, which has grown fast and
taller, are harvested by pulling them. After this, the smaller
plants get space (and sunlight and air) to sprout and grow fur-
ther, which allows a second harvest in 5–6 days after the first
one. Later, there is a third and final batch of harvest as the
plants left are finally growing. The two bunches harvested can
measure 0.007 m
3
and 0.66 kg.
For ‘matembele’ (the crawling type which have slimmer but
thicker leaves), the volume of harvest for one round is
0.003 m
3
, with a bunch weighing about 450 g. For ‘majani ya
maboga’ (pumpkin leaves), a perennial climbing and crawling
plant, germination is generally 7–10 days, with harvesting hap-
pening 2–3 weeks after. The harvest for one round is 0.003 m
3
,
weighing 300 g.
Corroborating the analysis of food derived, the Dar residents
admitted that ‘the structures are helping us as a garden where
we can get vegetables which could have been bought. It is easy
to take care, only just watering them. We usually harvest one
type of vegetable twice per week, we are doing three days rota-
tion to each type of vegetable, but it is for family use only ...we
never harvested for selling, unless a neighbour come to ask for
free’ (Interview 1, Dar, December 2020). Seeing the potentials for
meeting vegetable needs, an undocumented number of resi-
dents showed interested in the implemented prototypes. One of
such residents agreed that ‘we are also thinking about having
more structures because they are giving us vegetables and we
will only need to find money for spices’ (Interview 2, Dar,
December 2020).
Challenges of vertical greening in low-income
urban settings
Evaluation of the VGS implemented highlights important
issues. These are contained within overlapping experiences of
the interviewees from the different urban contexts. In addition
to the post-implementation interviews, feedback received
through phone calls, periodic check on the structures and
reports from neighbours show that the prototypes were gener-
ally well received, particularly for their potential to produce
food (vegetables). For vertical greening to be widely accepted
and scaled up, some challenges must be overcome. These chal-
lenges include as follows.
Low plant yield
It appears that the yield in some systems implemented was not
optimal. Expressing concerns, someone wondered that ‘since
we planted, they never outgrowing this level, though we have
Figure 2: Implemented PET bottle prototypes at Idi-Araba settlement, Lagos. Top
left: at Week 1. Top right: at Week 3. Below: at Week 5. Photo: Olumuyiwa
Adegun
Prospects and problems of vertical greening |3
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plucked from it ... It’s not taller than this, we need to know
why’ (Interview 1, Lagos, January 2021).
The yield problem is attributed to high solar insolation and
small size of the growth media. Two residents in Akure and Dar
identified this. The Dar resident notes that ‘the first challenge is
the sun, which cause the plants to dry’ (Interview 2, Dar,
December 2020). To another resident, there is a problem ‘on the
walls where the structures are located. It is directly exposed to
sun. As a result, too much heat causes the plants to shrink. This
changes in the evening because of sunset and cool weather’
(Interview 1, Dar, December 2020).
The growth media also constitute a limitation. On this, a res-
ident reported that ‘due to the container we are using, the
plants [vegetables] cannot really grow root downward very well
Figure 3: Design and illustration of the lattice prototype
Figure 4: Illustration of HDPE prototype
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compared to when it is on land ... But it’s still something we
can manage by putting cow dung and poultry waste’ (Interview
2, Lagos, January 2021).
High maintenance
VGSs require regular and proper watering for the plants to grow
well. Watering is done manually. Intensive watering is neces-
sary during the dry season for plants to survive. Regularly
watering demands time commitments and might be challeng-
ing when portable water supply is inadequate, which is a com-
mon challenge within slums. Climbing heights is another
difficulty with watering, and monitoring, the vertical gardens.
In one of the gardens in Akure, the highest HDPE pipe was not
watered and the plants dried because it was too high for the
short husband and wife (Interview 3, Akure, July 2020).
Limited blank walls/vertical surfaces
Installation of VGSs is usually preferred on solid blank walls for
strength and stability. There is a design trend of increasing fen-
estration sizes (especially windows) for improved ventilation in
residential buildings within the tropics. This reduces solid blank
wall areas available for vertical greening. A way around this is
to develop prototypes more suitable for non-blank walls.
Another worry was that external walls get damp, and might be
compromised structurally, through watering.
Pest and animal attacks
We observed that, like other vegetation, VGSs are subject to at-
tack from pests and straying domestic animals, which destroy
the vegetables’ leaves and affect their growth. ‘There is a dis-
ease which affects the plants. The disease can be transmitted
from one plant to another until the whole structure is affected,
...I hope there are pesticides to cure the disease. We need to be
educated’, a resident explained (Interview 1, Dar, December
2020). Getting the right pesticide that keeps the vegetables safe
for consumption is critical.
The green structures present a suitable attraction and habitat
for some animals—birds, lizards, snakes and insects. It is possible
that the animals’ interaction with the vegetation might further at-
tract them into the building through windows, roof and other
openings. Some animals, especially rats and goats, might feed on
the sprouting vegetables. These situations demand extra meas-
ures and resources to protect plants and buildings.
Economic considerations
Direct and indirect monetary benefits from vertical gardens are
important, from the livelihood perspective. Returns on funds
invested in installing the structure and cultivating the vegeta-
bles are considered. Returns are possible but, as observed, were
not significant on the scale of prototypes implemented. It is
therefore difficult convincing people to buy the vertical greening
from the livelihood perspective.
Socio-cultural dimensions
Some socio-cultural misgivings about growing vegetables on
walls emerged. These are mostly related to phobia and resent-
ment. For example, prototypes implemented within community
hall also used for regular religious services were removed when-
ever the services commence. The religious group was not con-
venient having those plants hung on the wall within the venue
during their service.
Vandalism
Some unscrupulous and/or careless residents damaged plants
in the prototypes. In Dar, this was attributed to jealousy. A resi-
dent noted that ‘jealous people are uprooting the plants because
they do not have such ... these are matured people who plan to
destroy the structure. We decided to relocate some to another
place’ (Interview 2, Dar, December 2020).
Tenure status
Installation of prototypes at times requires alteration to existing
fac¸ades. Tenants therefore need to seek and get approval from
landlord/house owners before execution. As a result, imple-
menting vertical greening by tenants is linked to the preference
of the landlord/house owner.
Concluding thoughts
Through this exploratory study, vertical greening has shown
potential in informal urban areas where there is usually conges-
tion and short supply of green spaces. It is additionally relevant
because urban agriculture is usually difficult to practice in
slums due to the lack of space and polluted conditions of the
soil. Yield gotten from the vertical farms’ production is low but
may be scale up with improved prototypes and better agronomy
system.
Furthermore, long-term measurement would be needed to
further establish other important variables that could positively
influence and improve prospects of vertical greening. Iterations
of the existing prototypes at improving plant yield and address-
ing identified challenges are important. Also, future studies can
Figure 5: HDPE prototype in Akure (A and E—‘tete’; B and D—‘ewedu’; and C and
F—‘shoko’). HDPE prototype at early stages of growth in Dar (A—mchicha; B—
matembele; C—majani ya maboga; and D—majani ya kunde)
Table 1: Cost analysis of VGS HDPE prototype
S. No Item Quantity Rate (N) Amount (N)
1. Wood (300 400) 3 470 1410
2. HDPE 400 pipes 5 2400 12 000
3. Stopper 10 300 3000
4. Nails n/a
a
400 400
5. Metal anchor 10 800 8000
6. Cement n/a 1350 1350
7. Aggregate n/a n/a n/a
8. Water n/a n/a n/a
9. Soil 1
1/2
bags 1000 1000
10. Workmanship (labour) n/a 2000 2000
11. Gum 1 1300 1300
Total 30 460
a
n/a: not applicable.
Prospects and problems of vertical greening |5
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monitor its contribution to micro-climate control and simulate
relevant scenarios.
While government/municipal structures at various levels in
Africa are trying to build parks and other green open spaces, usu-
ally in formal and affluent neighbourhoods, it is crucial to evolve
policy initiatives and programmes that promote citizen-led, com-
munity-based vertical farming in the dense informal settlements.
Incentives relevant for each local environment or community can
help the vertical greening innovation gain traction. There should
be a strong push for VGSs—for food, microclimate control and
other reasons—inside houses, on the roof or on the walls.
Acknowledgements
The study was supported through the Climate Research for
Development Fellowship Grant (CR4D-19-03) implemented by
the African Academy of Sciences (AAS). We acknowledge par-
ticipation and support from postgraduate students at the
Federal University of Technology, Akure, Nigeria, and Ardhi
University, Dar es Salaam. Statements made and views
expressed in this work are solely the responsibility of the
author(s).
Data availability
The data underlying this article will be shared on reasonable
request to the corresponding author.
Conflict of interest statement. None declared.
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Informal Settlement Intervention and Green Infrastructure: Exploring Just Sustainability in Kya Sands, Ruimsig and Cosmo City in Johannesburg
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Adegun, O. B. (2016). 'Informal Settlement Intervention and Green Infrastructure: Exploring Just Sustainability in Kya Sands, Ruimsig and Cosmo City in Johannesburg', PhD thesis, University of the Witwatersrand, Johannesburg.
Supporting Reblocking and Community Development in MtshiniWam. Interactive Bachelor of Science Qualifying Project
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Henning, Z., et al. (2012) Supporting Reblocking and Community Development in MtshiniWam. Interactive Bachelor of Science Qualifying Project. Cape Town: Worcester Polytechnic Institute.
Nigeria Enlists Big Beverage Companies to Fight Plastic Waste
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