growing greens at 5015 2nd avenue - librewebtools -...

GrowingGreensat5015/50112ndAvenue:Sub-IrrigatedPlantersforSustainableUrbanGardening

Overview

In the fall of 2013, CMU provided AHI and

the Pittsburgh Food Bank with technical

information, case studies and possible

layouts for a vegetable garden green roof

at 5015 2nd

Avenue in Hazelwood. More

recently, because of uncertainty about the

long-term use of this building as a grocery

store, AHI requested that CMU investigate

raised beds as an alternative approach to

vegetable gardening on this roof. Raised

beds do not require construction of a

green roof system and would allow

greater flexibility if building tenants

change. They are also scalable so that the

size of the garden can be adjusted to the roof load capacity.

CMU’s research on raised bed load requirements and other construction and maintenance

considerations eventually led to a focus on sub-irrigated planters (SIPs) as a scalable solution

well-suited to the project requirements: lightweight containers for vegetable gardening that are

portable, flexible in size and shape, conserving of water and soil nutrients, and reportedly more

productive than in-ground gardening. SIPs use a soil-less potting mix, so concerns about soil

contamination in a post-industrial city and its impact on food are substantially eliminated. SIPs

can be purchased or designed and built by hand, inviting creativity and innovation in their

construction and appearance. If the sphagnum peat moss in the growing medium is replaced

with a more sustainable material (more on this below), SIP gardening seems to be an excellent

choice for sustainability as well. Integrating SIP gardening into the renovation of 5015 2nd

Avenue introduces this relatively new urban agriculture method more broadly to the

Hazelwood community, providing an accessible, affordable approach that community members

can use to help shift Hazelwood from a food desert to a fresh food oasis.

For a basic introduction to SIPs and their benefits in urban gardening, see the 4-minute TED talk

video by Frieda Lim (Slippery Slope Farm) and Bob Hyland at

http://www.slipperyslopefarm.us/tedx-manhattan-2012.html

Figure 1 Sub-Irrigated Planter at Liberty Sunset Garden Center , a

public demonstration garden by Freida Lim and Bob Hyland in

Brooklyn, NY Photo credit: Steve Boling, website http://www.slipperyslopefarm.us/liberty-sunset-garden-center-sub-

irrigated-planter-systems.html


WhatIsaSub-IrrigatedPlanter(SIP)?

A sub-irrigated planter is a planting container one that has a water and oxygen reservoir at the

base of the container below the plants. Bob Hyland, a Brooklyn resident who founded the

Center for Urban Greenscaping (CUGreen) and blogs at http://www.insideurbangreen.org/

describes the SIP water and oxygen reservoir as a “scuba tank” for plants. The growing medium

above the reservoir is a lightweight soil-less potting mix that can wick water upwards from the

reservoir to the plants. Figure 1 shows one possible construction approach to raised bed SIP

with clear detail for the water/oxygen reservoir; the depth of this SIP can be effectively reduced

by cutting the bottom channels in half (half-pipe rather than whole, see photos and description

at http://www.insideurbangreen.org/2011/07/toronto-rooftop-sip-city-.html ). This diagram

appears in a fact sheet by Johanne Daoust. That fact sheet is available online at

http://www.pinterest.com/johannedaoust/urban-garden-sub-irrigated-self-watering-sips/ and

is also sent with this summary.

Figure 2 Example of Raised Bed SIP Construction

SIPGrowingMediaandWeight

Although sub-irrigation concepts are found in writings of Liberty Hyde Bailey more than 100

years ago,1 SIPs as we now know them appeared on the market in the early 2000s and targeted

1 For more information, see Liberty Hyde Bailey blog at http://libertyhydebaileyblog.blogspot.com/p/who-is-

liberty-hyde-bailey.html


vegetable gardeners. A company called EarthBox makes and sells SIPs (http://earthbox.com/ ).

An EarthBox is 29” long, 13.5” wide and 11” high. A filled EarthBox holds 3 gallons of water and

2 cubic feet of soil and weighs about 80 pounds. This means that the saturated load is

approximately 40 lbs/ft3. The components of that load are 12 lbs/ft3 of water, roughly 2

lbs/ft3 for the plastic container with built-in reservoir2 and 26 lbs/ft3 for growing mix. Although

SIP container design for 5015 2nd

Avenue may vary, one approach to estimating the saturated

load for a SIP garden at 5015 2nd

Avenue is to assume that the garden load will be some

multiple of a single EarthBox. As an example, the original green roof layout proposed by CMU

students (without information about or consideration of roof load capacity) showed 27 garden

beds occupying 1,620 ft2 of the available 4,524 ft2 roof area. The design included work space

between the beds and filled most of the roof except for an area near the alley and staircase for

HVAC equipment and garden storage. If the roof garden area were reduced to roughly one-

quarter of that space, there would be roughly 150 SIPs (based on the EarthBox specs given

above) with a total SIP weight of 12,000 lbs. The feasible multiple will be determined by the

building structural analysis.

The EarthBox website provides information about

commercially available growing media for SIP gardening.

The Daoust fact sheet and the websites cited here

describe possible components of a soil-less potting mix

more generally. As Daoust points out, the use of

sphagnum peat moss is not considered sustainable

because peat bogs are being over-harvested. A growing

medium that avoids that ingredient would be preferable.

Coir, made from coconut shells, is a potential substitute.3

Biochar, while not a substitute for peat moss, may be

another useful component of the SIP potting mix.4

WhatCanBeGrowninSIPs?

The picture to the left shows a “self-contained portable

micro-garden” growing on the steps of Chicago’s Museum

of Science and Industry. The garden is a series of EarthBoxes, and the picture appears on Inside

2 Estimate for container weight provided by EarthBox customer service at 888-772-4169.

3 http://www.vgrove.com/index.php?p=What_is_Coir

4 See Hyland blog section under Biochar heading at http://www.insideurbangreen.org/sub-irrigation-aka-self-

watering/page/6/ including the link to the International Biochar Initiative at http://www.biochar-

international.org/biochar . Since SIPs do not contain soil, the biochar benefit in SIPs needs to be explored further.


Urban Green blog at http://www.insideurbangreen.org/smart-home/. Because the SIP growing

media is lightweight, there do not appear to be limitations to the types of vegetables (based on

root depth) that can be grown in SIPs at 5015 2nd

Avenue. Given the considerations of overall

rooftop load capacity, the use of shallow-rooting greens and herbs may be advantageous to

maximize the total garden expanse and yield. According to the Guide to Setting Up Your Own

Rooftop Garden (published by Alternatives and the Rooftop Garden Project in Montreal with

funding from the Public Health Agency of Canada, 2008), 20 cm (approximately 8”) is sufficient

depth for growing tomatoes and lettuces can thrive in 15 cm (6”) of soil/growing medium.

There is ample published information on urban gardening and root depths for vegetables and

herbs. The Food Bank may want to engage community members in choosing the plants for the

rooftop of 5015 2nd

Avenue, using the total SIP volume allowed by rooftop load capacity to

determine the number and types of containers and plants that will be installed. The Guide

cited above discusses the importance of including perennials in the garden for the beneficial

insects they attract.

WateringRequirementsandRoofDrainage

SIP gardening conserves water. EarthBox provides a comparison of tomato gardening in-

ground versus SIPs that shows slightly more than 30% savings.5 Hyland claims that SIPs use 90%

less water than overhead watering (http://brooklynbased.com/blog/2010/08/05/the-best-urban-

gardening-method-youre-not-using/). Because water is stored below the root zone in SIPS,

evaporation is said to be a minimal problem. However SIPs are not “self-watering” although

they are sometimes mistakenly referred to that way. SIPs are watered via the fill tube that

extends from the sub-root reservoir to the top of the container and they must have a drain

tube at the bottom. From a design perspective, this means that water must be provided to the

roof of 5015 2nd

Avenue and SIP drainage must be planned.6 An automatic watering system can

connect multiple SIPs and this approach is probably most effective for 5015 2nd

Avenue. The

Guide to Setting Up Your Own Rooftop Garden cited above offers examples of automatic

watering systems. The Guide also recommends rooftop storage for gardening supplies.

OrganizationandStaffingforaCommunityRooftopGarden

Hazelwood and the Pittsburgh Food Bank already have experience in community gardening.

The 2008 Guide cited above provides useful information about planning a rooftop garden

layout and coordinating garden efforts and workers throughout the year. While it does not

5 The comparison sheet is linked to the Green Roof Growers blogspot at

http://greenroofgrowers.blogspot.com/2008/07/how-to-make-sip.html 6 Currently, the roof slopes toward drains in the middle of the roof but water ponds there, particularly on the north

side of the roof.


specifically address SIPs, the Guide does discuss container gardening in Chapter 6. It also

diagrams a multi-container watering system and offers examples of successful rooftop garden

installations in several locations. A copy of the Guide will be delivered with this summary.

Cool(er)RoofMembranes

In the green roof recommendations prepared for

AHI and the Food Bank last fall, CMU students

mentioned Cool Roofs, a servePGH initiative that

made resources available to nonprofit organizations

to coat their own roofs, helping them to save on

energy costs and lower their carbon footprint. That

program has ended, but an initial review of roof

membrane literature suggests that the incremental

cost of a higher reflectance roof membrane can be

less than the energy savings such a membrane

offers. Since there will be substantial areas of the

roof that are not occupied by the garden, the energy impact of the roof membrane deserves

consideration. CMU will provide more information about this in its summary of roof insulation.

InsidetheCaféat50112ndAvenue:Year-RoundOptions

In Montreal, a company called Jard’IN has designed and installed wall-based planters that use

pipes for containers and framing that includes grow lights to produce a “crop” of herbs and

greens in less than 20 days. At a recent visit to Patisserie La Ruche at 4500 Avenue du Parc,

CMU saw one of the Jard’IN installations and learned that at La Ruche, the herbs and greens are

used in the foods they serve. It may be possible to combine the concepts of indoor SIPs with

wall-based planters to provide year-round vegetables and visual interest for the café at 5011

2nd

Avenue. Hazelwood community members and/or students could be involved in their

design, perhaps as a design competition. A selection of picture from Jard’IN’s website is

provided below. More information is available at https://fr-fr.facebook.com/jardinside

Figure 3: Community Garden with SIPs. Photo credit:

EarthBox, http://earthbox.com/community-gardens


AFewAdditionalLinks

ExamplesofSIProoftopgardens

http://www.insideurbangreen.org/rooftop-gardening/

http://archives.rooftopgardens.ca/index.html%3Fq=en%252Fourgardens.html

http://www.gardenstateurbanfarms.com/our-beginning/ (Garden State Urban Farms began as Brick City

Urban Farms in Newark. There are some similarities between the initial food desert conditions in

Newark and in Hazelwood. See a short video about Brick City at http://earthbox.com/community-

gardens )

DesignIdeasforSIPS

http://greenroofgrowers.blogspot.com/2008/07/how-to-make-sip.html (also includes some history of

their development)

http://www.insideurbangreen.org/sub-irrigation-aka-self-watering/ (indoor SIPs)

growing greens at 5015 2nd avenue - librewebtools -...

Documents