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Zane Middle School edible landscape

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Figure-1: The Rainbow Walkway in Eureka California
Figure-1: The Rainbow Walkway at Zane Middle School.

The purpose of the project is to create an edible landscaping that will help incorporate the STEAM (Science, Technology, Engineering, Art, and Math) program that Zane Middle School focuses their curriculum around. The edible landscaping will be an example of the engineering process necessary to create an edible landscape as well as a space for educating students about plants and their care.

Background[edit | edit source]

Team Seedling is composed of four Humboldt State University students: Tanya Garcia, Jax Gill, Jared Goebel and Danielle Holter. They are currently enrolled in the spring semester of 2014 Engr215 Introduction to Design taught by Lonny Grafman. The group is collaborating with Zane Middle School to create an edible landscape on campus that will be utilized by students and community members through out the year. The edible landscape must be aesthetically pleasing so that it attracts students and sparks their interest with nature.

Problem Statement and Criteria[edit | edit source]

The objective of Team Seedling is to add sustainable edible landscaping to Zane Middle School's campus. This landscaping should be low maintenance and child friendly while providing educational value and awareness of the local and native environment. Table-1 lists the criteria that were created along with the specifications and considerations emphasized by Zane Middle School. The criteria are weighted on importance which aids in making the final design decision.

Table-1: Criteria and Description
Criteria Weight Description
Educational Value 10 Provide educational tools, that include plant names, various facts and class curriculum that connect the project to nutrition and students' lives
Safety 9 No possible projectiles unless in areas where students are supervised, does not block supervisor's lines of visibility
Maintenance 8 <1 hour per month, low to no water after 1st year
Aesthetics 7 Better than status quo, pleasing to the eye
Cost 6 Total < $900, maximize plants per square yard
Cleanliness 6 Does not litter pathways, minimizes pest attraction

Description of final project[edit | edit source]

The Rainbow Walkway is a half oval or "rainbow" consisting of shrubs aligned on the east side of the garden. Within the half oval there is a semicircle with shrubs, ground cover, a bench and a wooden pamphlet holder. There's a 9 foot walk way between the two beds, thus creating a rainbow shape. There are five trees, two of which are to the right of the rainbow and to the left are the other three trees in a triangle shape, equidistant from each other. There is another bed against the northeast fence of the school garden which consists of blueberries, grapes, and ground cover. Thanks to donations and discounts from various sources, this design fits perfectly within the budget. The layout is aesthetically pleasing because of the immense contrast in colors and easy to mow around.

The Rainbow Walkway has three berry planters and five tree planters. There is the half oval berry planter on the east side of the garden containing 3 salal, 2 flowering currant, 2 rosemary, and 2 borage, shown in figure-2. The two flowering currants will become the larger shrub for this bed and provide beautiful pink flowers.[1] Salal was used as a native groundcover.[2]Borage, with its blue star shaped flower, was chosen to incorporate edible flowers into the design and for contrast against the flowering currant.[3] Rosemary was chosen to add a nice smell to the space while also providing contrast to the flowering currant.[4] The bench and pamphlet holder are also placed in this planter, as it is centrally located.

Figure-2: Half Oval Planter.
Figure-2: Half Oval Planter.

There's a 9 foot walk way behind the oval followed by the rainbow shaped berry planter. The rainbow planter, shown in figure-3, contains 8 Chilean guava, 8 Oregon grape, 6 wild strawberry, and 10 huckleberry. Chilean guava was chosen as a sweet late fall producer.[5] Beach[6]and woodland[7] strawberries were chosen as a native groundcover. Two different varieties were included in case one did better in Zane Middle School's microclimate. Dwarf Oregon grape was chosen for its colorful flowers.[8] Huckleberry was planted behind the Oregon grape to provide color contrast and due to that level of shade provided by the existing trees in the back of the landscape.[2]

Figure-3: Rainbow Shaped Planter.

The last berry bed is on the north side of the garden fence, containing 12 blueberries, 2 himrod grapes, 1 interlaken grape, 3 yerba buena, and 3 checkerbloom, as shown in figure-4. Blueberry was chosen and planted in such large numbers because it is a berry most students already know and feel comfortable eating. It is placed closer to the rainwater catchment system because they may need more water than the other species when first being established.[6]Himrod[9] and Interlaken[10] grapes were chosen to help add some beauty to the bare metal fence they will grow on.Yerba Buena[11] and checkerbloom[12] were chosen as a native groundcover to showcase edible leaves.

Figure-4: Planter Along Garden Gate.
Figure-4: Planter Along Garden Gate.

There are three trees north of the blueberry bed in a triangular shape. The last two trees are bordering the right side of the Rainbow Walkway. Two peach trees were chosen for their delicious flavor and the Frost variety was chosen because it is known to do well this close to the coast.[6] Two varieties of apple tree were spaced apart from one another to reduce the chance of a disease possibly affecting both of them.[13] The Asian pear tree provides extra variety into the garden. Figure-5 shows a peach tree and figure-6 a pear tree.[14]

Featured below in figure-7 is an image of the inside of the pamphlet for the Rainbow Walkway. Figure-8 shows an image of the outside of the pamphlet.

Costs[edit | edit source]

Below is Table-2 which shows the costs of materials purchased to implement The Rainbow Walkway. The table breaks down the quantity of each item purchased as well as the retail cost and the amount paid by the group. Thanks to local businesses, Wes Green Landscape Materials, Miller Farms Nursery, Lost Foods Native Plant Nursery and Pierson Building Center, the net cost was decreased by more than a total of $350 dollars.

Material Cost[edit | edit source]

Table 2-Cost of materials
Material Source Quantity Cost Per Unit ($) Total Retail Cost ($) Total Team Cost ($)
Grapes Piersons 3 5.09 15.28 15.28
Huckleberries Lost Foods Nursery 10 5.00 50.00 0.00
Blueberries Miller Farms Nursery 12 10.00 120.00 91.08
Chilean Guavas Miller Farms Nursery 8 10.00 79.92 63.92
Oregon Grape Lost Foods Nursery 8 5.00 40.00 0.00
Frost Peach Tree Miller Farms Nursery 2 28.99 57.98 57.98
Honeycrisp Apple Tree Miller Farms Nursery 1 24.99 24.99 24.99
Liberty Apple Tree Miller Farms Nursery 1 22.99 22.99 22.99
20th Century Asian Pear Tree Mad River Gardens 1 27.99 27.99 27.99
Flowering Currant Lost Foods Nursery 2 5.00 10.00 0.00
Salal Lost Foods Nursery 3 5.00 15.00 0.00
Strawberry Lost Foods Nursery 4 5.00 20.00 0.00
Yerba Buena Jared Goebel's Backyard 3 5.00 15.00 0.00
Checkerbloom Lost Foods Nursery 3 3.00 15.00 0.00
Rosemary Flying Blue Dog Nursery 2 3.75 7.50 7.50
Borage Flying Blue Dog Nursery 2 3.75 7.50 7.50
Soil Test kit N, P, K, pH Ace Hardware 1 20.65 20.65 20.65
Fence Board Piersons 3 3.75 11.25 0.00
Landscape Edging (20 ft) Miller Farms Nursery 12 20.90 250.90 214.72
Wood Sealant (gal) McKenny's Do It Best 1 43.09 43.09 43.09
Screws Jared Goebel's Backyard 10 0.00 0.00 0.00
Wood Blocks Jared Goebel's Backyard 5 0.40 2.00 0.00
Metal Hinge Piersons 1 5.40 5.40 5.40
2x6 Redwood (ft) Piersons 4 1.69 6.76 0.00
4x4 Redwood (ft) Piersons 6 2.39 14.34 0.00
Cement 50lb Bag McKenny's Do It Best 2 4.30 8.60 8.60
Wooden Stakes McKenny's Do It Best 18 0.59 10.67 10.67
Stakes Miller Farms Nursery 10 0.88 8.88 8.88
Mulch Wes Green Landscape 3.3 cu.yd. 39.09 129.01 129.01
Compost Wes Green Landscape 2.3 cu.yd. 45.00 103.50 13.50
Top Soil Wes Green Landscape 0.3 cu.yd. 14.10 14.10 14.10
Total Cost $1,168.20 $787.84

Labor Cost[edit | edit source]

The pie chart below shows the total amount of time in hours spent on the project by the Team Seedling team members. It is divided into 5 parts, each representing a different phase in the project.

Figure-9: Labor Hour Pie Chart.
Figure-9: Labor Hour Pie Chart.

Maintenance[edit | edit source]

In the following table the estimated amount of time is shown for each task related to maintaining the landscaping. The grounds keepers workload will increase by an estimated 15 minutes due to more obstacles to mow around and the rest of the maintenance will be done by volunteers and teachers. The total cost of maintenance is $17.57 for a box of fertilizer per year and the extra amount of gas necessary.

Table-3: Maintenance Chart

Table-3: Maintenance Chart
Task Responsible Time (min/month) Material ($/year)
Mowing Maintenance Crew 15.0 Gas - $8.58
Weeding Students 20.0 None - $0.00
Harvesting Students 30.0 None - $0.00
Pruning Volunteer 15.0 None - $0.00
Fertilizing Volunteer 3.0 Fertilizer - $8.99
Total 83.0 $17.57

Results[edit | edit source]

The result is a beautiful, low maintenance landscape at Zane Middle School filled with a variety of delicious edibles. It has informational pamphlets, for community education, and accompanying curriculum, to ensure student involvement and education.

The finished design of the Rainbow Walkway in Eureka California
Figure-10: Panorama of Rainbow Walkway at Zane Middle School.

How to build[edit | edit source]

When creating your own edible landscape, it is important to follow every step listed.

Edible Landscaping
Steps Instructions
Step 1: Choose a Location
Figure-11: Location of Rainbow Walkway at Zane Middle School.
Figure-11: Location of Rainbow Walkway at Zane Middle School.
Depending on where the edible landscaping is being implemented, choosing the location can be simple or at times complex. It could be as easy as a garden in a backyard or possibly a trickle of edible landscaping throughout an entire school. When choosing the location it is important to choose and objective or goal for what is about to be created. Examples of objectives are: beautifying an area, producing enough food for a cooking club, producing enough food to attract wild life and creating an educational space for children. An important consideration when creating an objective is your budget.[15]
Step 2: Analyze Solar Exposure & Climate
Figure-12: A website that can help you calculate the amount of sunlight a location receives.
Figure-12: A website that can help you calculate the amount of sunlight a location receives.
Once the location is chosen it is time to analyze the environment. The amount of sun exposure can be measured with ones eye by writing down when the sun begins to touch the soil and when it ends. Determining cardinal directions (North, East, South and West) along with which direction the sun rises and sets are very important. There are also online applications that can help determine sun exposure for your potential location.

Important considerations for climate are rainfall, humidity and temperature. Rainfall is a limiting factor to the plant's growth and a lack of rainfall can cause plants to wither if there is no human watering. Humidity affects plant turgor pressure which is the amount of water in plant cells. When humidity is low, moisture evaporates quickly causing the plant to wilt; when humidity is high (along with higher temperatures) plants will overheat which can reduce the evaporative cooling. Also with high humidity comes plant diseases such as fungi and molds which can grow quickly. Fleshy fruits and vegetables need colder temperatures and a higher humidity level to prevent water loss, which ultimately causes shriveling.[16] The average annual temperature for the location should be considered and is helpful because plant selection should depend on what can survive in the area's temperatures.

Step 3: Analyze Soil Conditions
Figure-13: Man collecting soil for soil test.
Figure-13: Man collecting soil for soil test.
Soil is the literal foundation upon which the landscaping will grow from. It is important to test the soil. Knowing this, necessary amendments can be made to the soil. Such amendments range from bringing in new soil, adding more organic material, supplementing nutrients, or leaving it alone. Some studies have shown soil that maintains its native characteristics, leads to a better overall life of larger woody trees.[15]
Step 3a: Test Physical Soil Conditions
Figure-14:Physical Soil Jar Test.
Figure-14:Physical Soil Jar Test.
Soil type is defined by how much sand, silt, or clay it has. Figure 13 shows these three components settled in separate layers, silt is labeled as heavy clay. Sand is the largest of the three, which allows water to pass through it quicker. Clay is very fine and holds water in. Too much sand means soil will lose water too quickly, and too much clay can suffocate plants. Silt is between the two in size but acts more like sand. Silt is helpful in balancing out the sand and clay.[15]

To test the sand, silt, and clay levels:

  • Fill half of a quart mason jar with soil, removing organic matter
  • Fill other half with water
  • Allow soil to soak up water and then shake
  • Let it sit for 2 minutes, then look at with flashlight to see how much sand has settled
  • Let it sit for 2 hours, look at with flashlight again. Bottom is sand, middle is silt, and the top is clay
Step 3b: Test the Soil's pH and Nutrient Levels
Figure-15: Soil Nutrients Test.
Figure-15: Soil Nutrients Test.
The pH of the soil determines a number of characteristics such as water holding capacity and nutrient availability for the plants. Most plants have the best nutrient absorption between a soil pH of 6.0-7.5. To test pH levels a test can be purchased at most local nurseries or garden supply stores.

The most important nutrients for plant growth are nitrogen, potassium, and phosphorous. Without these nutrients, a plant cannot grow properly.[15]To test nutrient levels a test can be purchased at most local nurseries or garden supply stores.

Step 3c: Test the Soil for Heavy Metals
Figure-16: Scientist testing for chemicals.
Figure-16:Scientist testing for chemicals.
Heavy metals can be very harmful when consumed in large amounts. If heavy metals are suspected the soil should be sent to a lab for testing. If testing is not done and levels of heavy metals are suspected, it is recommended that plants are placed a minimum of 20' from buildings where lead based paint is suspected and 100' away from roads and parking lots. Fruit and seed, particularly from woody plants, contain the lowest levels of lead and arsenic, followed by roots and tubers. Increasing the organic matter in soil and neutralizing the pH can slow plant uptake of heavy metals. It is also recommended that people working in the garden wash hands afterwards and that all harvested food be washed, as soil can contain up to 1,000 times greater heavy metal concentrations than plants residing in the same soil. To test for heavy metals a soil sample must be taken to a lab and tested by professionals, which can be found on the internet. At home kits can also be bought online.[17]
Step 4: Explore Plant Options
Figure-17: An example of an edible flower, borage, is shown.
Figure-17: An example of an edible flower, borage, is shown.
Once growing conditions are known it is time to choose plants that have the best chance of surviving and thriving within the space.

When considering a plant in the context of edible landscaping, seven factors are weighed:

  • Size
  • Texture
  • Food availability throughout the year
  • Competition
  • Growth at maturity
  • Form
  • spacing of plants
  • Color

Other considerations of plant selection include the location of edges and borders, walkways, and the existence of supplemental or support structures.[18] When selecting plants, availability should be considered. Options for sourcing plants include local nurseries, farmers markets, mail order nurseries and sourcing from the wild. Using nurseries, both mail order and local can be great, however consideration as to the origin of the plants should be made because diseases can be easily spread from region to region.[19]

Step 5: Create Potential Designs
Figure-18: AutoCAD drawing of a potential design.
Figure-18: AutoCAD drawing of a potential design.
Now that research has been done one should have a list of possible plants to use. One can then create two to four different designs that incorporate a variety of plants. Plants are generally divided into four types:trees, shrubs, herbaceous plants and ground covers, and vertical growers or vines. The more you incorporate the different types together, the better the edible landscaping.[20] This is the time to research the spacing between each plant and also the shallowness the roots prefer.
Step 6: Choose the Design that Meets the Objective Best
Figure-19: Team Seedling's delphi matrix.
Figure-19: Team Seedling's delphi matrix.
Analyze the designs you have created against your goals. There are several tools to help with this if you need, one useful one is the delphi matrix
Step 7: Purchase Materials
Figure-20: Some materials needed to begin a garden/landscape.
Figure-20: Some materials needed to begin a garden/landscape.
Once the design is chosen the materials must be purchased. The materials can be split up into two groups; tools and items that will end up in the ground.

Necessary tools include: Pickaxe, Shovel, gloves, tape measurer, watering can and stakes. What is needed for the landscape is; compost or fertilizer, mulch, water, and a barrier option: Edging, Vinegar or Buffer.[20]

Step 8: Begin the Implementation Process
Figure-21: Tanya Garcia breaking some ground.
Figure-21: Tanya Garcia breaking some ground.
Implementation consists of various sub-steps. Tools such as a tape measure, shovel(s), gardening gloves and a pix ax may be needed.
Step 8a: Staking
Figure-22: Staking out bed
Figure-22: Staking out bed.
The first step of implementation is staking where your bed will be placed, using a tape measure and stakes. One can begin by staking the corners of the bed and then adding two or three stakes towards the center perimeter. The stakes will help when laying out edging.[20]
Step 8b: Tearing Soil
Figure-23: Blueberry bed after tearing up soil with pick ax.
Figure-23: Blueberry bed after tearing up soil with pick ax
Once the location is set any existing plants and turf must be removed. This process can mostly be done with a shovel however, compaction of soil varies and may call for other tools such as a pick ax or rototiller. After removing all the turf and weeds, continue digging so that it is easy for the roots and air to move through the soil.[20]
Step 8c: Establishing Borders
Figure-24: Putting edging into place.
Figure-24: Putting edging into place.
There are various ways to establish borders within a garden. Some methods include brick, concrete, edging or even vinegar around the beds. These all have different affects on the plants biological state and the landscapes overall aesthetics. If mowing will be done around the planter beds, it is important to dig deep enough so that the edging has space to sink in and is not higher than the the turf level.[20]
Step 8d: Spacing Plants
Figure-25:Spacing Blueberries Equidistant from One Another.
Once the bed is clear of all turf and the borders are in, the plants can be placed in their intended planting spot. Every plant is different and the amount of space needed between each plant varies and should be researched in Step 5. Dividing the length of the bed by the number of plants is a good way of placing plants equidistant.
Step 9: Planting the Plant
Figure-26: Student patting down soil after filling hole.
Figure-26: Student patting down soil after filling hole.
With a shovel, dig appropriately deep holes for each plant. Next take the plant out of its container. This can be done by holding it upside down with the stem in-between ones fingers and using the opposite hand to softly squeeze the container. This should loosen the soil enough so that the plant slips out easily. Now loosen the bottom roots a bit with a tickling motion and place in hole. It is very important that before you fill the hole that you water each individual plant for at least 5 seconds. After this is done the soil can be placed back into the hole.[20]
Step 10: Apply Compost or Fertilizer
Figure-27: Applying a layer of compost.
Figure-27: Applying a layer of compost.
Compost and fertilizers add nutrition to the soil. Where you place these depends on the selected plant. Some prefer for the compost to surround their roots and others do well with a surface layer. When applying a surface layer of compost it should be from one to two inches and spread across the bead evenly.[15]Placing a thin layer of newspaper is optional to further the prevention of weeds[20].
Step 11: Apply Mulch
Figure-28: Toddler applying layer of mulch on blueberry bed.
Figure-28: Toddler applying layer of mulch on blueberry bed.
When choosing mulch it is important to consider any easy sources readily available, as well as the potential to hold weed seeds, permeability, thermal effects, stability, and the desired aesthetic.[20]Some good options are wood chips, hay and straw, manure, excess leaf cover and compost. Apply an even layer of mulch on top of the soil or fertilizer along the entire bed. It is also important to consider mulch depth, a general rule of thumb suggests between 1"-2" once settled, although more may be used to encourage soil building and to protect roots from foot traffic.[15]

Discussion and next steps[edit | edit source]

About this project
Translation data

Discussion[edit | edit source]

Once The Rainbow Walkway was chosen obstacles slowly started popping up and caused for change in the design. The original design had the open side of the rainbow facing North West and created a sad face with the two trees on the right hand side. The direction of the bed had to be changed because vehicles needed to be able to access the entrance to the garden. After this change had been made the concern of breaking fire regulations arose. The peach tree on the left side of the bed would have to be moved to make the back of the building accessible for fire fighters. Luckily after a month, it was determined that the tree was not breaking code and would not have to be moved. Thanks to donations, twelve blueberry plants could be added along the fence creating an entire bed rather than just three vines.

Figure-29: AutoCAD drawing of a original Rainbow Walkway design.
Figure-29: AutoCAD drawing of a original Rainbow Walkway design.

Next Steps[edit | edit source]

Now that The Rainbow Walkway has been implemented all there is left to do is wait for the plants to grow. As the plants begin to fruit and spread, it is up to the school and its volunteers to keep the plants thriving.

Video[edit | edit source]

Update October 2014[edit | edit source]

Since the panorama picture at the top was taken, a few things have changed at this edible landscape. Near the bench, which was donated to the middle school, there is a new wooden post made from re-claimed wood which contained brochures about the edible landscape. The brochure contains information on some of the species of plants there, when they are ripe, a blueberry jam recipe, a "how to" guide on creating your own edible landscaping, and a summary on what it is. A picture of the brochure is located below. (Note: The picture of the brochure is black and white because we got a copy from Trevor because we did not want to waste one of their color copies). Some species that are here include: chilean guava, wild strawberries, liberty apples, evergreen huckleberry, blueberries and Oregon grapes. Trevor Hammons, a counselor at the middle school, told us that the whole project was less than $100 total because much of the materials had been donated. The Zane Middle School rainwater catchment system supplies all the water needed to water the plants, creating a self-sustained edible landscape.

New/Minor Issues[edit | edit source]

The plants have grown and there have been a small number of issues or problems with the landscape project. Two signs had been stolen and an animal mauled one of the peach trees. The school counselor also noted there was a small concern about the wood chips and students possibly throwing them at each other, but there has not been an issue of the sort to date. Another minor issue is maintenance since there is no maintenance crew on this campus, so all the watering and weeding has to be done by the students, faculty or staff at the school. However, Trevor informed us that this is not a big issue because the students are able to learn more about gardening and responsibility.

Edible Landscaping Brochure[edit | edit source]

  1. United States Department of Agriculture. (2008). "Red-Flowering Currant.", <http://plants.usda.gov/factsheet/pdf/fs_risa.pdf> (May 2, 2014).
  2. 2.0 2.1 Benoliel D. (2011). Northwest Foraging, Skipstone, Washington.
  3. West Coast Seeds. (2013) "Borage." (May 2, 2014).
  4. West Coast Seeds. (2013)., "Rosemary." (May 2, 2014).
  5. One Green World. (2014). "Chilean Guava.", <https://www.onegreenworld.com/product.php?id=1336&> (May 2, 2014).
  6. 6.0 6.1 6.2 Armstrong, S. (2013). "Fruits of the Humboldt Bay." California.
  7. Missouri Botanical Garden. (2014). "Fragaria vesca.", <http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=b346> (May 5, 2014).
  8. Aoki, M., Coggins, J., Fisher, P., Hess, E., Koester, H., Lytjen, D., Newhouse, B., Otting, N., and Robert, (2005). Native Shrubs in Our Garden, Native Plant Society of Oregon, Oregon. Shady Situations, 16. <http://emerald.npsoregon.org/NGAPguides/ShrubsBooklet.pdf>
  9. One Green World. (2014). "Himrod.", <https://www.onegreenworld.com/product.php?id=1817&> (May 2, 2014).
  10. One Green World. (2014). "Interlacken.", <http://web.archive.org/web/20130619011428/http://www.onegreenworld.com/Table%20Grapes/Interlaken/2684/> (May 2, 2014).
  11. United States Department of Agriculture. (2014). "Yerba Buena", <http://www.fs.fed.us/wildflowers/plant-of-the-week/clinopodium_douglasii.shtml> (May 3, 2014)
  12. Plans for a Future. (2012). "Sidalcea malviflora.", <http://www.pfaf.org/user/Plant.aspx?LatinName=Sidalcea+malviflora> (May 2, 2014).
  13. One Green World. (2014). "Honeycrisp™ M-26 .", <https://www.onegreenworld.com/product.php?id=59&> (May 2, 2014).
  14. Dave Wilson Nursery. (2014). "20th Century Asian Pear", <http://www.davewilson.com/product-information/product/20th-century-asian-pear> (May 2, 2014).
  15. 15.0 15.1 15.2 15.3 15.4 15.5 Ellefson, C., Stephens, T., Welsh, D., (1992) Xeriscape Gardening., Macmillian, New York.
  16. North Carolina State University. (2013). "Humidity.", <http://www.nc-climate.ncsu.edu/edu/k12/.humidity> (Feb. 22, 2014)
  17. Peryea, F. (2001) "Gardening on Lead- and Arsenic-Contaminated Soils" <http://web.archive.org/web/20170712103415/http://www.ecy.wa.gov/programs/tcp/area_wide/AW/AppK_gardening_guide.pdf> (May 2, 2014).
  18. Creasy, Rosalind. (1982) The Complete Book of Edible Landscaping., Sierra Club, San Francisco California.
  19. Slawson, D. (2008). "Number 1 - Sourcing Plants." NT Plant Quarantine & BiosecurityGuidance Note. Washington State University, <http://web.archive.org/web/20100608120752/http://www.puyallup.wsu.edu/ppo/sod/extension/gardens/NTguidelines/NTGN1%20-%20Sourcing%20Plants%20Final.pdf> (Feb. 25 2014).
  20. 20.0 20.1 20.2 20.3 20.4 20.5 20.6 20.7 Jacke, D., and Eric T. (2005). Edible Forest Gardens, Chelsea Green, White River Junction Vermont.