URBAN AGRICULTURE TECHNOLOGY
This document presents topics relevant to urban agriculture technologies. The topics are:
Green houses & food treatment
1. Green houses & food treatment
A building, room, or area, usually chiefly of glass, in which the temperature is maintained within a
desired range, used for cultivating tender plants or growing plants out of season.
Greenhouses evolved from Orangeries – a structure developed for nobility some 300 years ago,
“partly because of fashion, and partly because weather seemed to be colder than it had been in
previous centuries.” An Orangerie, much like a greenhouse were constructed to create a warm space
that could create a ‘summer’ environment and where the nobility could entertain during the colder
months. Moreover, projects like Kew Gardens demonstrate a desire for human desire for worldliness.
Residents of a colder climate wished to possess the beauties of warmer nations. By 1824, the
popularity of greenhouses was gaining momentum all across Europe, no longer reserved for the
highest elite, they were being used more and more for horticulture purposes.
Greenhouses in Québec:
The Conseil de production végétale du Québec states that a greenhouse must be able to support its
own weight, as well as that of any covering, wind load, snow load, and the produce load without
significantly interfering with light. As well, it must be efficient in heating and ventilation, while allowing a
sufficient amount of space for cultivating and the work involved. Moreover, it must be agreeable in
appearance and be as cost efficient as possible.
There are two principal kinds of greenhouses – the traditional greenhouse and the ‘hoop house’.
Where the hoop house acts more as protection and thus requires minimal heating and ventilation
systems to minimally maintain environmental parameters to slightly prolong the growing season (late
March to October), the traditional greenhouse’s goal is more to cultivate in all seasons through optimal
control of climatic conditions, which must be more precise.
For the emplacement of a traditional greenhouse, in a rural setting, one must consider many factors –
these considerations don’t differ too much in an urban setting. The topography must be more or less
flat, no more than a 1% slope, the area must be large enough to house the greenhouse, the
connected buildings and storage. There are two significant factors that should dictate the orientation of
the greenhouse – the wind and the light. Winds have less significant impact on a greenhouse that is
orientated in the same direction as the dominant winds, this eases the mechanical ventilation of the
greenhouse. In Québec, most of the dominant winds blow from West to East, however, at times, larger
structures (especially in an urban setting), can affect their direction, thus these should be investigated.
East-West greenhouses benefit from more significant light in the winter months, however, this light is
less consistent in other months than a North-South orientated greenhouse. Still, if the goal is a year-
round production, it is preferable to orient the greenhouse on an East-West axis ± 15º.
It would not be preferable to build a greenhouse in an urban context, as, for lighting purposes, a
greenhouse should be distanced by 2.5 times the height of an obstacle. Also, in order to avoid
accumulation of snow, it is preferable that a greenhouse be at least 30 m away from obstacles.
Elevating a greenhouse would do a lot to rectify these issues, allow for construction in a more urban
setting. To avoid inundation, facilitating the evacuation of water should also be important.
For more information on the actual structure of a greenhouse for a Québec climate, please refer to
Serre: Construction et aménagement pages 20 to 30. For more information on the most preferable
equipment for year-long production in our climate, refer to pages 31 to 70.
Most preferable species:
Because of the constraint environment that is a greenhouse, small compact plants are most
preferable, especially in an urban setting where there is not much room for the implementation of
many structures. From an economic perspective, should we wish to yield a profit from a greenhouse,
the most cost effective vegetables would be cucumbers, tomatoes, peppers and strawberries, as they
do not require much room and do give a significant yield. However, is profit is not the goal, but rather
the greenhouse is to be an aspect of Community Sustained Agriculture (a project that may or may
not be started through government funding, but that is managed by the community), the crop could be
expanded to include bok choi, cabbage, lettuce, snap peas, radishes and beets, onions, broccoli.
Berry shrubs are also feasible. Fresh herbs are most likely the easiest plant. Vine plants as well as
root vegetables are not preferable for an urban greenhouse environment.
Weather effects (salt and cold):
In climates like Montreal, the roads are heavily salted in winter. The spray from streets on plants can
be very damaging if the plants are sensitive to salt. The leaf buds may stop opening, and road-facing
sides may die altogether. Luckily, there are plants that are more tolerant of salt. There are many
trees, vegetable, and vines that will all survive outside in salty environments – notably vines like
grapes and honeysuckle will.
The table below is an example of vegetables and their salt tolerances.
Table 1. Relative salt tolerance of vegetables*
12 mmhos 10 mmhos 4 mmhos
beet tomato radish
kale broccoli celery
asparagus cabbage bean
10 mmhos 4 mmhos 3 mmhos
* Relative salt tolerance decreases down each column,
e.g., tomato is more salt tolerant than cucumber.
Another factor of Montreal weather is the cold. There are plants that are especially hearty in cold
weather and will not be killed by a frost. The best are beets, Brussels sprouts, carrots, collards, kale,
parsley, and spinach. For more information on what vegetables will survive best in our climate, check
out the attached links.
Many of the vegetables we eat may not be local, but the First Nations people fed themselves off the
land for years. Plants such as wild greens, seaweed, roots and bulbs, and berries have been grown
naturally in Canada.
Heating alternatives info:
Greenhouses in temperatures like Montreal require alternate forms of heat in the winter months as the
sun is more often than not, not enough. To make them more economic and use less energy from
fossil fuels and other non-renewable resources, methods used to heat homes can be applied to
greenhouses as well. For example, solar heat, bio-diesel, and wind power can be used to heat
Compost heat can be harnessed by attaching a compost to a greenhouse. This also increases the
CO2 levels for better plant growth, something that is normally done by machines.
For greenhouses on rooftops, the escaping heat from air-conditioning and heating units can be
transferred over to heat the greenhouse fairly simply.
The Science Barge:
The Science barge is the pet project of scientists and engineers from the New York Sun Works, a non-
profit organization. They implemented, in the Hudson River Harbour, “a sustainable urban farm
powered by solar, wind, and biofuels, and irrigated by rainwater and purified river water.” The
vegetables production produces no carbon emissions, no net water consumption and no waste
stream. The vegetables also require seven times less land and four times less water than regular rural
farming processes. At this time, it is one the most innovative and successful example of urban
agriculture for a climate similar to that of Québec. For more information on the Science Barge,
New York Sun Works is also playing an important role in Building Integrated Agriculture and Controlled
Environment Agriculture. You can check out their website:
Since 1990, container growing, mostly in what is called pépinières (greenhouse-like structures), has
been rapidly gaining popularity in Québec. Traditionally, container growing is defined as cultivating
plans in a pot, outside the soil, during a gestation period and until the definitive planting by the user.
The plant must spend at least one gestation period in this pot, that its roots might spread and utilise
the whole container so it becomes easier to transfer, later, into soil.
However, as McGill’s Edible Landscapes project has demonstrated
(http://www.mcgill.ca/mchg/pastproject/el/), it is entirely feasible in an outdoor urban area, to produce
plants for consumption in one growing season as a Community Sustained Agriculture project. Before
undertaking such a project, one must be conscious of the availability of water, wind protection,
topography, cost of terrain, availability of labour, and distance from markets and services (if it is to be
economically viable). In Québec, we can expect to be able to keep growing containers outside from
about end of May to early October. Therefore there must be buildings available to keep the plants
during the winter months. For more detailed information on the specifics of container growing, the
Conseil des productions végétales du Québec’s books Pépinière: Culture en Containeurs –
Planifications, Pépinière: Culture en Containeurs – Hivernage, and Pépinière: Culture en Containeurs
– Irrigation provides excellent step by step information on the process.
Biotop Canada (www.biotopcanada.com)
Composting has a variety of methods, for small spaces, indoor spaces, and urban spaces.
Basic city composting is done in bins with tight fitting lids and bases and no openings large enough for
animals, to keep pets away. The containers can be made of metal, plastic, or reinforced wood.
The first step of composting is to add 3-4” of woody material to get air to the bottom of the pile, not to
be mixed in. Add 2-4” layers of green and brown materials alternately, until the bin is full. Green
material is classified as nitrogen products, such as grass or food scraps. Brown material is carbon
material, like leaves, newspaper strips. Add a thin soil layer whenever adding a green layer to the top,
to prevent smell and animals. Mix bin at least every two weeks, combining old and new materials and
adding air for faster decomposition. Continue until bin is full, cover with carpet to retain heat and
moisture. Compost will be ready after 2-3 months, but letting is sit for another month or two is
Worm composting is an easy indoor alternative. It can be done indoors or out, and in small buckets,
so is great for apartments all year round. Just add moistened bedding and worms to container, and let
sit. Add your food waste and over time it will become rich soil.
Rainwater can be collected with very little extra effort. After being channelled through downspouts and
eaves troughs, it can be collected in large cisterns and used when needed. A roof can collect up to
0.62 gallons/square foot of roof footprint/inch of rain.
Rainwater can also be used after treatment for potable uses. A concrete cistern can filter the water to
meet national standards. The water is filtered through sand, treated by activated carbon adsorption,
and disinfected by an ultraviolet treatment unit before being stored in a large storage tank. Before
being pumped into fixtures the water is disinfected again.
With limited space in urban environments, fruit trees often take up too much space to be feasible.
Espalier is a technique that has been used for centuries, to grow fruit trees in 2 dimensional planes.
The ability to grow trees against walls not only saves space but can create more fruitful trees. Most
trees grown in this manner are grown with grafted dwarf root stock, so that the trees are smaller,
although the fruit remains the same. This means that pruning and fruit collection are easier.
Planting against walls can extend the plants’ growing season. Because the growing wall will both
reflect and absorb heat, the plant is exposed to heat longer than a freestanding tree. Another
advantage of espaliering is that more of the plant is exposed to direct sunlight. This results in more
flowering and more fruit.
The best varieties to try this with are apple or pear trees, but it is possible with fruits such as plums or
cherries. The best locations to grow are along faces that receive direct sunlight in the summer but are
protected in the winter. And east facing wall will work for this. The process requires care but is
relatively simple. Heavy wire is strung up at 0.5 to 1.0 meter intervals, and the branches are trained to
grow along these. The trellises can be freestanding or connected to buildings.
The diagram below illustrates the steps of creating an espalier.
For greenhouse construction :
Conseil des productions végétales du Québec. Serres : Construction et aménagement.
Gouvernment du Québec, 1994.
Kurth, Heinz and Geneste. Greenhouses for Longer Summers. Prentice-Hall Canada Inc,
Scarborough, Ontario. 1982.
Northeast Regional Agricultural Engineering Service. Greenhouse Systems – Automation,
Culture and Environment. Cooperative Extension, Ithica, New York, 1994.
Northeast Regional Agricultural Engineering Service. Greenhouse Engineering. Cooperative
Extension, Ithica, New York, 1994.
Agriculture Canada. Energy-conserving urban greenhouses for Canada. Ministry of Supply and
Services Canada, 1987.
Health and Welfare Canada. Native Foods and Nutrition. Ministry of Supply and Services Canada,
For container growing :
Conseil des productions végétales du Québec. Pépinière : Culture en conteneurs –
planification. Gouvernement du Québec, 1993.
Conseil des productions végétales du Québec. Pépinière : Culture en conteneurs – irrigation.
Gouvernement du Québec, 1993.
Conseil des productions végétales du Québec. Pépinière : Culture en conteneurs – hivernage.
Gouvernement du Québec, 1993.
2. Green Roofs
”A green roof is a green space created by adding layers of growing medium and plants on top of a
traditional roofing system. This should not be confused with the traditional roof garden, where planting
is done in freestanding containers and planters, located on an accessible roof terrace or deck.”
A green roof system has several layers, which include, from the top to bottom:
• “The plants, often specially selected for particular applications,
• An engineered growing medium, which may not include soil,
• A landscape or filter cloth to contain the roots and the growing medium, while allowing for water
• A specialized drainage layer, sometimes with built-in water reservoirs,
• The waterproofing / roofing membrane, with an integral root repellent, and
• The roof structure, with traditional insulation either above or below.”
”Green roofs can be designed to be an integral part of a new building, or can be installed later on an
existing building. When a building is designed with a green roof system, there can be several benefits.
For example, the building is designed to provide the necessary structural support, and won't require
reinforcement later. Also, the building can be designed to take advantage of the aesthetic value that a
green roof can offer by providing viewing areas.”
Green roofs have been an integral part of construction systems throughout the world, in both cold and
warm climates, at both large and small scales. Earlier examples include the hanging gardens of
Babylon which consisted of 3 acres, spread out over seven stories spanning 75 feet vertically.
In Scandinavia, the roofs of wooden houses were garnished with sod to insulate them from the cold
In the 20
century, Le Corbusier experimented with green terraces, and the designs of the Rockefeller
Center in New York and the Union Square in San Francisco both incorporated green roofs.
The green roof industry has recently taken off with the introduction of more efficient building materials,
especially when it comes to insulating membranes, as well as a growing environmental consciousness
since the 1960s.
Currently, the green roof industry is ahead in Europe, in contrast to North America. In Germany, the
demand for green roof technology grew significantly in the 1980s. The government presented
incentives to the public, such as paying households 35 to 40 Deutsche Mark per square meter of the
roof area, which was converted to accommodating greenery.
There are several categories of green roofs, and it is important to distinguish them. There are
complete systems, modular systems and pre-cultivated vegetation blankets.
“In a complete green roof system, all parts of the roof are designed to support vegetation
growth. These systems provide the most flexibility in terms of the type and nature of growing
medium, drainage and protection layers and type of vegetation. Complete systems vary in
thickness and weight from as low as 50mm to 75mm (2 to 3 inches) in depth and 60 to 90 kg
per sq. m, (12 to 18 lbs per sq. ft.) in weight. They can be installed with a variety of
waterproofing membrane types.”
Complete systems break up in two important categories, the intensive and extensive green
roofs. Table 1 outlines the differences between these two systems.
Source: Design Guidelines for Green Roofs, p. 7
The following schema portrays the differences between the intensive and extensive roof types.
Source: Architectural Record 03.03, p. 150
“Modular systems are essentially trays of vegetation in a growing medium that are grown off-
site and simply placed on the roof to achieve complete coverage. They are available in
different depths of growing medium typically ranging from 75mm to 300mm (3 to 12 inches).
The variety of vegetation is typically more limited.”
Emerging technologies focus on modular systems, seeing that the implementation is easy and
requires less effort than the complete green roof system. An example of such a technology is
the Biotop System. Especially designed containers permit plants to develop two sets of root
system, permitting plants to grow to full maturity without transplanting them. More information
is available at http://www.biotopcanada.com.
Pre-cultivated vegetation blanket
“A pre-cultivated vegetation blanket is a pre-grown interlocking green roof tile. The blanket
shown below is available in a thickness of about 45mm (1.75 inches).
Blanket systems are available in a variety of system designs. The most versatile system
contains 25 mm (1 inch) of planting substrate. The result is a lightweight system ranging in
weight from 40 to 60 kg per sq. meter.
The majority of the vegetation is made up of several varieties of Sedum, a succulent plant (8.0
to 13.0lbs per sq. ft.) tolerant to extremes in temperature that survives with little or no irrigation
while requiring very little maintenance. They are cultivated at ground level, then rolled and
transported as a complete system on pallets or by crane.”
There are many benefits to having a green roof. All sources point these out unanimously.
For a building owner, a green roof can present the following benefits:
The green roof protects the building from direct solar radiation, and helps prevent inside
temperature from rising. This in turn lowers the energy bill required for cooling the building. In the
winter, the added cover and insulating membranes needed in the roof installation help conserve
Roof membrane protection and life extension:
The presence of a green roof may double the lifespan of the roof by protecting it against large
fluctuations in temperature, UV rays and pedestrians.
The growing medium helps block lower frequencies of sound, while the vegetation blocks part of
the higher frequencies. This could be applicable to noisy residential areas, such as near airports.
Some studies show that green roofs slow down the spread of fire, since the growing medium is
wet or humid.
Additional usable space:
Green roofs permit to creation of additional recreational areas or retreats for the elderly or patients
The roofs permit the production of “high quality organic foods, and medicinal and ornamental
plants. This has the advantage of reducing associated transportation and refrigeration costs,
reducing the time and distance from field to table, ensuring ripeness at harvest, and providing new
employment opportunities for city dwellers.” This is clearly the case in McGill’s Edible Landscape
Green roofs also profit the general public in several ways.
Urban heat island effect:
Urban and suburban areas tend to overheat in the summer because of the important presence of
dark, asphalt-paved surfaces, which absorb heat. This leads to an over-consumption of energy to
cool down habitable areas. Green roofs permit to absord or reflect the solar rays and reduce the
temperature in cities.
Storm water retention:
This aspect is particularly relevant to Montreal. When it rains, the water is collected in the city’s
sewage system. In Montreal, during excess water accumulation, the sewage system releases the
water into the St. Lawrence and Des Prairies Rivers – which obviously has environmental
consequences. Green roofs permit to accumulate some of the water, or at least prevent it from
going directly into the sewage system. Additionally, the rain water is filtered by the green roof, so
the runoff is cleaner.
Not only do green roofs permit additional conversion of CO2 to O2, but the plants also capture
airborne polluting particles.
Creation of habitat:
Green roofs can accommodate specifies of plants and animals, such as birds and insects, that
would otherwise lack shelter or a habitable space.
See pages 10-18 in the Design Guidelines for Green Roofs, at http://www.cmhc-
for a complete breakdown of variables to consider when building a green roof, such as maintenance,
laws and cost estimates.
An extensive list of green roofs is available at the following website:
The following site is the most comprehensive source, especially for this project. Although many
sources were consulted, the following one really proved to be the most complete and adapted for
understanding the basics of green roofs.
Similar information (almost identical) was also found in the following book, published in French. It is an
especially good source for local Montreal projects and discussing local laws when it comes to green
”Toitures vertes à la montréalaise”, by Maude Landrevile, available at the Blackadder-Lauterman
Two other sites proved to be good, and have more links to yet other useful pages.
3. Vertical Gardens
At the turn of the twentieth century, Gertrude Jekyll, inspired by the Arts and Crafts Movement in Great
Britain, starts planting vegetation in the cracks and crevices of stone walls. Almost one hundred years
later, Patrick Blanc, the pioneer behind the modern vertical garden creates hydroponic living walls
after observing how vegetation can grow on soilless surfaces (cliff sides, rocks, tree trunks) in
Malaysia. His vertical gardens can turn the banal wall of a city into “a valuable shelter for biodiversity.”
Patrick Blanc’s Mur Vegetal manage to weave very natural ecosystems into the urban fabric in a very
dynamic and innovative manner.
Patrick Blanc’s vertical gardens were the catalyst for a new form of horticulture and gardening. A
great example of this is ELT Living Wall Systems, who are based out of Brantford, Ontario. ELT
began as a company that manufactured easy-to-assemble green roof tiles, and now they also provide
modular living wall panels for both pre-grown and planted vegetation—all you need is soil and your
plant of choice. The vertical garden tile is made in way that will retain soil, but allow for the even
distribution of water and nutrients. The pockets slope downwards and have grooves that will push the
water to the back so that the roots can get the necessary food and stay moist. Water is poured into
the panel from the top and then trickles down to the bottom where excess water is caught in a catch-
The ELT living wall panels can be used to grow anything from ornamental grasses to flowers to
vegetables and herbs and can be arranged to created very interesting textures and patterns. The
panels are made of UV resistant 100% Recyclable black High Density Polyethylene.
The MFO park in Zurich Switzerland is an exemplifying project that uses the notion of gardening
vertically. Burckhardt + Partner and Raderscall Landschafts architekten designed what has been
dubbed an “urban park”, where a lightweight metallic lattice structure has been built for the growth of
vines. Visitors access the structure via stairs, reaching a sundeck, loggias, and cantilevered lookouts
that give an overhead glimpse of the space below. At this lowest level are benches, pools, and the
start of the vines following cables that taper outwards in a conical shape towards the roof. Depending
on the time of year one visits, the vegetal "walls" are sparse, full, or colorful.
4. Urban Livestock
Potentially positive and/or negative aspects of animal keeping:
Positive (or negative) Negative (or positive)
- produce (healthy) food - dung and urine disposal
- use waste / clean or scavenge
- disease risk
- provide income and emotional
- status, savings, tradition - zoonoses / hygiene
- dung for garden - nuisance
- draught - much work
René van Veehuizen, ed., Cities Farming For the Future. RUAF
Opportunities and Barriers to Urban Livestock Keeping in the North America:
* Little known, unknown, and/or illegal experience on which no information is available
* Disparate and un-coordinated legal codes at municipal level on urban livestock keeping
* Space restrictions
* Inadequate knowledge and/or unsafe (eg. unsanitary) practices
* Cultural resistance to raising animals for food and other economic purposes
* Often practised by marginalised groups and regulated by elite groups.
* Survives because of economic need, cultural endurance, and social resistance
* Produces fresher and tastier meat
* Experiences brought by immigrant and rural migrant communities
* Local dialogue between practitioners and regulators can proceed in tandem with new
development at international level
* Species for small areas like fish, guinea pigs, rabbits, and chickens incomplete
* Technical training; workshops; community engagement in urban livestock
* Community-wide food systems education
* Community dialogue on food security needs
René van Veehuizen, ed., Cities Farming For the Future. RUAF Foundation, 2006.
Feasible Animals for The City:
Aquaponics is a system where fish and plants are raised in the same system. (see the Growing
Power section under Precedents for an explanation of how a system would work)
Talapia-Relatively adaptable, although they prefer warm water. They eat algae, salad, and worms.
They are easy to raise, and marketable to restaurants.
Yellow Perch-They are bottom feeders, and will therefore eat almost anything. They prefer cooler
water and are a favorite among chefs.
A simple re-circulation system can be as small as 4ft x 4ft. (see
http://www.webofcreation.org/BuildingGrounds/aqua/TOC.html for information on how to build
one) and can sustain 20-30 tilapia fingerlings.
Worm (red wigglers) compost; a nutrient rich, organic fertilizer and soil conditioner.
Produces compost with a higher nutrient ratio than any other composting method.
Worm castings are rich with microbial life which aids in breaking down nutrients already in the soil
into a form that plant roots can absorb.
Worm mucus helps soil hold moisture better and keeps nutrients from washing away.
Worms can be raised in bins or piles of soil, and therefore require minimum overhead and
Worms eat food waste (twice their body weight/day) and multiply rapidly.
Requires little room.
See http://www.growingpower.org/worms.htm for more information.
One hive contains appx. 60,000 bees and produces appx. 150 lbs. honey/year.
Requires little room.
Helps produce bigger fruit and vegetables.
Require appx. 4 sq. ft./chicken
One chicken lays appx. one egg every 25 hrs.
Improves garden health
Suppresses pests and weeds
Builds soil fertility
Produces much fresher eggs than are sold at the regular supermarket
Require 60 sq. ft./goat
Requires appx. 20 minutes of care per day
Can be used for dairy (milk, butter, yogurt, cheese) or sold for their meat to ethnic groups.
Eat leftover vegetable waste
See http://www.goselfsufficient.co.uk/keeping-a-goat.html for more information.
-The Fairmont Royal York, Toronto, Ontario
-3 queen bees and 10,000 worker bees are residing in the 14
story triple hive apiary.
-Executive chef David Garcelon in partnership with Toronto Beekeepers’ Cooperative and Foodshare
will deliver local sustainable honey to hotel guests.
-The bees are a natural extension of the existing roof-top herb garden.
-They encourage more flowers, healthier plants and bigger fruit.
-See http://radioroyalyork.ca/2008/06/the-fairmont-royal-yorkencourages-urban-bee-havior/ for more
-The Fairmont Waterfront, Vancouver, BC
-2 queen bees and 120,000 worker bees are residing in the “Honey Bee Suites” which are adjacent to
the 2,100 square foot herb garden located on the third-floor terrace.
-The honey is used in the hotel’s food dishes as well as in its bar where it is incorporated in their
-See http://www.edible-britishcolumbia.com/blog/?cat=8 for more information.
Growing Power, Milwaukee, WI:
-Non-profit Urban Agriculture and Education Facility
-Grows enough food for 2,000 people on 2 acres
-Raises tilapia, yellow perch, worms, bees, chickens, goats, ducks, and turkeys.
-Tilapia and yellow perch are raised in tanks whose water is drained into a gravel bed where
watercress and bacteria break down the ammonia into nitrogen. The water is pumped to the growing
beds and then back to the fish tank. The system is easy to build and only requires a small pump and
heat to run.
-See http://www.growingpower.org/ for more information.
Some Relevant Heifer International Projects
-The Toronto Beekeepers Cooperative
-3 hives were given to The Toronto Beekeepers Cooperative and Foodshare in 2002; they are
currently keeping 12 hives with a few hundred thousand bees
-They passed on 3 hives to the Everdale Environmental Learning Centre in 2003 to “pass on the gift.”
-The bees contribute to more productive urban fruit and vegetable harvests as pollinators are not
abundant in cities.
-This provides a local source of sugar, reducing the demand for imported sugar cane whose
production is responsible for more biodiversity loss than any other crop worldwide.
-For most people in the city, this is the only accessible way to learn beekeeping.
-Healing bee products, creams, salves, lip balm, honey-wine and candles are also produced.
-See http://www.foodshare.net/download/Urbanbees.pdf for more information.
-Just Food’s City Farms Program, New York City
-Teaches low-income neighborhoods how to grow their own produce and livestock and then allows
them to sell it for profit at City Farms Markets.
-Have recently developed a City Chicken program which promotes the best practices of raising
chickens in the city and teaches people how to build coops and city regulations.
-See http://www.justfood.org/cityfarms/chickens/ for more information.
-ReVision House Urban Agriculture, Dorchester, MA
-Provides job training, transitional housing and education to homeless young mothers and their
-Market-based urban farming program
-Aquaponic system produces tilapia and herbs. The three story back porch of the reVision house was
converted into a solar greenhouse where hydoponic systems were constructed.
-Apiculture (honey bees)
-See http://www.vpi.org/Re-VisionFarm/ for more information.
-Cabrini Greens Project, Chicago, IL
-Kids from the Cabrini Greens housing project grow produce and raise chickens, goats, and ducks
-Currently raising the funds to buy a pasteurizing machine so that cheese can be made from the goats’
-Expecting two bull calves to plow their land.
-See http://www.growingpower.org/chicago_projects.htm and
http://www.metropolismag.com/html/content_1098/oc98risk.htm for more information
WHAT IS HYDROPONICS?
Hydroponics is a method of growing plants by using a water and nutrient solution instead of soil.
The term is derived from the greek word ‘hydro’ meaning water and ‘ponos’ meaning labor. Almost
any plant will grow using hydroponics, but there are some that are more practical and take to it better
than others. Examples of such plants are fruit bearing crops, leafy crops such as lettuce, herbs and
“The hydroponic greenhouse vegetable industry has a growth rate of 10 percent per year and
accounts for nearly 95 percent of the greenhouse vegetables produced in North America.”
BENEFITS OF HYDROPONICS IN URBAN AGRICULTURE
-More plants can be grown in a given space
-Less water used since none is consumed by weeds (5% of the water soil would use!)
-Plants can be stacked vertically
-No soil born disease
-Grow year round
-More control over nutrient levels equals better produce
-Plants need different amounts of water depending on what stages of growth they’re in
-Combine raising fish with hydroponics by attaching a fish tank to the system and instead of having to
clean the fish tank the waste can be cycled through the system and used as plant food.
WHAT IS NEEDED?
1. The Growing Medium -used mainly for starting seedlings
-the less amount used the better in terms of cost
-ideally reuseable or biodegradable
-porous, clean, no effect to pH balance, drainable
-aims to hold an equal amount of air and water
-ex: vermiculite sawdust, peat moss, sand, perlite (air puffed glass pellets), rockwool (molten rock
spun fibers) coconut coir (from coconut husks) perfect starts (molded sponge made from organic
compost and a biodegradable binder)
In soil nutrients come from rocks, minerals, animal waste, and decomposing plants and animal matter.
Soil provides a buffer to the plants, so in hydroponics if something is wrong with the solution the plants
will be effected instantly.
-Roots need air!
-Roots absorb oxygen and in turn emit carbon dioxide.
-It is important the roots receive air to maintain health and avoid rotting as well.
HOW IS IT DONE?
There are many different hydroponic techniques.
-plants suspended in channel of solution
-solution flows through one end of the tray and back into the reservoir through the other
-roots not completely submerged but only at the bottom
-requires a pump
-a power outage will kill most of the plants and is a large drawback
-nutrient solution drawn into a growing tray holding a medium from a larger reservoir by a wick
Water Culture System
-floating styrofoam platform holds plants
-air pump supplies oxygen to roots of plants, which are kept in the solution
-mainly good for growing lettuce
Ebb and Flow System
-flooding and draining the growing tray by pump connected to a timer
-solution cycles from the trays to the reservoir
-flooding and draining can be set specific to the plant type and time of day
-similar power outage drawback
-nutrient solution is dripped onto plants from a reservoir containing a submerged pump
-in a recovery drip system excess solution returns to the reservoir
-a non recovery drip system requires less attention because the nature of the solution isn’t changed
each time it is collected from the plants
-roots hang in the air and are misted with the nutrient solution
Current Hydroponic Development
“we’ve stacked up people but we have not stacked up farming”
“In selecting a greenhouse site, a grower must be aware of several chemical properties that
might cause problems for greenhouse growers: pH, alkalinity, soluble salts, calcium,
magnesium, boron, fluoride, chloride, sulfates, sodium, carbonate, and iron. The cleaner the
water, the greater the opportunity to achieve maximum yields. The water designated for use in
a greenhouse must be analyzed for agricultural suitability during greenhouse site selection.”
“Computers can operate hundreds of devices within a greenhouse (vents, heaters, fans, hot
water mixing valves, irrigation valves, curtains. lights. etc.) by utilizing dozens of input
parameters, such as outside and inside temperatures, humidity, outside wind direction and
velocity, carbon dioxide levels and even the time of day or night. Unlike early control systems,
computers are used today to collect and log data provided by greenhouse production
managers. A computer can keep track of all relevant information. such as temperature,
humidity, C02, and light levels. It dates and time tags the information and stores it for current
or later use. Such a data acquisition system enables the grower to gain a comprehensive
understanding of all factors affecting the quality and timeliness of the product.
Whatever the source of energy, it should be conserved once it is in the greenhouse. In regions
of cold winter weather, thermal curtains of porous polyester or an aluminum foil fabric are
installed to reduce night heat loss by as much as 57%. In the deserts of the southwest, winter
temperatures are not severe enough to warrant curtains. While curtains will provide energy
savings, they are not sufficiently effective to warrant their high cost. Furthermore, the shade
from the curtains, even when rolled up and stored during the day, can reduce yields.”
Merle H. Jensen Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
One of the key advantages of hydroponics is the level of control over plant needs. Control
over the amount of light is often reached using grow lights, since hydroponic systems are ideal
for growth indoors.
“Metal halide grow lights consist of an arc tube made of alumina, inside of which is
argon, mercury vapor and a variety of metals. The different metals give color to the
light the lamp produces. The argon gas is used to get the lamp going at first when
electrical current is introduced inside the arc tube from electrodes on either end. The
arc of current vaporizes the metals and mercury, and thus light is produced. The
benefit of using these lamps is that for such small bulbs they produce a lot of light,
and are efficient to run.
HPS grow lights are also called high-pressure sodium lights. Like the MH lights, HPS
lights also use an alumina arc tube. Inside this tube you will find sodium, mercury, and
the noble gas Xenon to get the light started. Like the metal halide lights, HPS lights
also require a ballast for their use, to stabilize their operation.
LED grow lights are similar in function to the lights you might see on Christmas trees
during holiday times. They are a small, efficient and very bright light. The diode
functions as a semi-conductor, and there are two crystals in this type of bulb. LED
bulbs light up when electrical current moves from one crystal to the other. The light
produced is surrounded by a reflector and is used with a lens to emit the light where
you want it to go.”