Rooftop Gardening

So want to have an organic garden, but, alas, your backyard is shadier than a politician. But you have noticed that the deck spends all day basking in glorious sunshine. Or perhaps you want a garden but have no backyard, placing responsibility for such an adventure squarely upon the roof. 

There’s a good chance that your deck is sturdy enough for the weight of garden beds, and it’s possible that even the roof is up to the task, but there are a series of essential factors to address that could very well mean the difference between pleasant mornings harvesting lettuce on the roof, and a fleet of emergency response vehicles, and perhaps a news reporter or two, racing to your home.

Simply put, you can’t just put what could add up to thousands of pounds of wood and soil above your living space, cross your fingers, and hope the roof doesn’t cave in.  Whether new construction, or reinforcing an existing building, a structure must be designed for the additional weight of a roof top garden, and any people using the garden. 

This equation involves not just the size and spacing of joist or rafters, but all the components of a building that are required to transfer that load down to the foundation, including: plywood roofing, rafter/joist sizes and span, girders, columns, walls and footings. 

For example, in order to evaluate a joist or girder, one needs to know the amount and type of load it supports, how far it spans and its size, type of material and its properties (allowable bending and shear stresses, etc).

It may not always be practical or cost effective to make changes to a structure in order to accommodate a roof top garden.  The main difficulty with a retrofit is the ability to determine if your home is actually strong enough to hold it up.  Most homeowners literally have to open up the walls and ceiling to find out.  If you live in a typical single family residence, chances are good your home’s roof  was not made to hold that much weight and you will need to add extra supports to accommodate a rooftop garden. Most decks, however, are capable of carrying the load of raised beds or other planters.

For a safe, rewarding rooftop gardening experience, follow these steps:

-determine that there is adequate sunlight and drainage on your roof or deck. Multifamily and commercial roofs and terraces will most likely have drains placed in low areas where water can be channeled into a gutter system
-determine how many people will be on the roof at one time, and how they will get up and down.
-address any HOA guidelines or concerns, and consider any other liabilities that could be an issue like your roof’s warranty, for example.
- Create a layout of the rooftop garden, including dimensions and volume of raised planters.
-Determine the weights and loads the rooftop garden design, as well as the estimated number of people would place on your building.
- Size or check the building members (beams, rafters, etc) from the roof down to the foundation

It’s always best to have a professional evaluate your structure to determine if it can safely bear the load of a garden, the basic science of it boils down to evaluating your roof or deck’s ability to support three weight categories :  dead, live or environmental loads.

Dead loads are weighted items that will be there all the time, including the materials in the actual roof or deck itself.  Typical rooftop garden  dead load types and their weights are:
        *Self weight of the structure - load varies
        *Conventional roof - 7 to 10 psf (pounds per square foot)
        *Small plants - 2 psf
        *Drainage layer - 2 to 3 psf
        *Soil density - 60 to 110 pcf (pounds per cubic foot) loads vary depending on soil mix

Live loads are dynamic or moveable loads associated with an areas usage -  In this case, mainly people.  Code dictates that different roof types be able to hold different amounts of weight.
        *In-accessible landscape roofs - 20 psf
        *Private or residential roofs - 40 psf
        *Multifamily or commercial roofs - 100 psf

Environmental loads such as snow, wind, seismic, rain, etc. Consider that your roof is most likely to fail during a rainfall when your garden’s grow medium is fully saturated.

Starting Seeds Indoors

While starting your own vegetable  plants from seed might not be as fulfilling as a life dedicated to fighting world hunger or forest fires,  it is pretty darn cool watching you’re your tiny seeds sprout grow into sturdy seedlings destined to yield produce for the kitchen table.

Starting Seeds Indoors

1.Start by filling a flat with grow medium  to within ¼” of the surface and level with a piece of wood.

2.Spread the selected seed variety evenly over the soil, and press down with the flat side of the piece of wood.

3. Cover the seeds to the depth specified on the packet – typically a depth of about 4 times their diameter - taking care to spread an even amount of soil over the seeds.

4.Again using the piece of wood, gently press down on the surface of the soil, and water it with a fine mist. The soil should be moist, but not soggy - like the consistency of a wrung out sponge.

5. Seal in moisture by covering the flat with a plastic dome or bag, and place it in front of a south facing window, or under florescent lights set to run 18 hours per day.  Because the flat is covered, you shouldn’t to need to water the soil until the first seedlings emerge and the dome or plastic bag is removed. Remove the plastic cover once the first seeds sprout.

Creating Ideal Conditions for Germination

-Place seedlings sear a sunny, south facing window, and/or under cool florescent lights set on a timer to run 18 hours per day. If plants are near a window, remember to rotate them regularly to ensure even growth. Seeds sprouted on a window without direct sun exposure will stretch and become spindly. If a south facing window isn’t convenient or unavailable, it’s best to invest in florescent lighting.

-Most seeds germinate best in a temperature range of 70-75 degrees, and sprouted seedlings prefer room temperatures of 60-70 degrees.

-Once the first sprouts have emerged, and the plastic cover has been removed, check the soil every day for lighter colored spots, which indicate that it is drying out. Gentle overhead watering with a fine mist is okay, but soaking the flat from the bottom carries less risk of damaging the tender young seedlings.

-The first set of leaves to emerge are called cotyledons which are actually food storage cells. As the seedlings continue to grow, the first set of true leaves will emerge. At this point, it’s time to fertilize the plants with an organic fish emulsion or seaweed based plant food.

-Seedlings can be thinned or transplanted when they have developed four true sets of leaves.

Special Seed Treatments

Some seeds require special handling to achieve good germination and growth.

-Scarification is a technique where the outer shell of the seed is scored with a knife, making it easier for the sprouted plant to emerge.

-Soaking seeds in warm water over  night improves germination. Remember to limit soaking to 48 hours as they may rot beyond that. Varieties that prefer soaking include corn, beans, okra, cucumber, melons, peas and squash.

-stratification involves changing the environment around the seeds to recreate natural weather cycles. Place seeds in a sealed plastic bag with about 4-5 times their volume in most peat moss or vermiculite, and place in the refrigerator for cold stratification or on a window sill for warm stratification. Once tiny white primary roots have emerged, the seeds are ready to be sown into sterile potting mix.

- Rhizobium  inoculant treatments added to bean seeds before planting will encourage a more vigorous plant capable of converting more atmospheric nitrogen into a usable form for the plant.

Bokashi Composting

Bokashi translates “fermented organic matter” in Japanese, and is a composting method that uses anaerobic bacteria in an airtight container to compost food scraps in indoor settings where traditional composting would be difficult - like a kitchen, apartment or garage.

While traditional composting relies on both aerobic and anaerobic bacteria to complete the decomposition process, the bokashi fermentation process happens in a closed system, which controls insects and smells. Unlike traditional composting, where the presence of dairy, bread and meat scraps would certainly attract rodents and create horrific odors, the bokashi process efficiently breaks down these items right alongside more familiar compost items like vegetable peelings and coffee grinds.

Billions of lacto-bacillus bacteria break down the scraps without the presence of oxygen, and because the system is sealed, no greenhouse gases are released, and no nutrients are leached away. This means that your garden’s soil will get the full benefit of the bacteria, sugars and nutrients in the finished compost, and because the anaerobic bacteria multiply so rapidly, the bokashi method happens much faster than traditional composting, creating a powerful amendment that’s ready to be integrated into your soil in around two weeks.

Sounds amazing right? It is, but remember that while the bokashi method has the unique ability to quickly break down meat and dairy as well as vegetable scraps in controlled settings ( sealed in an airtight plastic container),  for those who live on even a modest sized property, it would be all but impossible to compost the high volumes of leaves, grass clippings, old plants and other waste your yard produces using this method. Folks who own land will likely still need an outdoor compost station that is large enough to handle these plant based materials.

Tips for success using the bokashi method (courtesy of Bokashicomposting.com )

• The smaller the scraps that go into the composter the better.  Smaller scraps have more surface area and will break down faster relative to larger scraps.
• Use more bran for harder objects like bone, avocado skins, and corn cobs.
• Keep the composter out of the direct sun and away from direct heat sources.
• The optimum temperature for bokashi fermentation is 70-100 degrees Fahrenheit.
• Keep the lid closed tightly.  The process is anaerobic, so the less air exposure the better.
• Compress and compact food waste inside the bucket to remove air space.
• Cover the top layer of the waste inside the bucket with a plastic bag to help decrease air exposure.
• Conditions are not the exact same for everyone.  So feel free to experiment.  Let your nose and eyes be the guide.  White mold is good, green is bad.   A sweet pickled smell is good, a rancid odor is bad.  More bran, smaller waste piece, more surface contact, and warmer temperatures can help to correct these conditions.

Gardens and Coops Make Great Gifts

Casey Rogers had been interested in organic gardening and raising backyard chickens for some time, but it wasn’t until around the time last fall when “Rocking around the Christmas Tree” saw a sharp spike in airplay, that Courtney Rogers decided a coop and garden would make a really cool gift.

The goal was an attractive looking organic garden large enough to yield organic produce year round for the family of four’s dinner table. We went with an L shaped Kitchen Garden style bed measuring 4’ wide by 10’ on the long sides, with a 4’x4’ square bed nestled inside the larger bed.

The Rogers's garden is located on a slightly sloping area on the edge of their property and while it receives plenty of unfiltered morning sunlight, clusters of nearby trees will offer a reprieve from withering afternoon heat in the summer.

The Beds are made with 2x12 Western Red Cedar boards, and filled with a blend of pine bark fines, mushroom compost and Stalite PermaTill. To the soil we add Microfarm Mix : an organic amendment blend of bone meal, blood meal, kelp meal, green sand, dolomite lime, and rock phosphate.

The Rogers’s also wanted a small flock of three to five hens that will provide a dozen or more organic eggs every week. That’s easy enough, but because the Rogers family lives in an upscale neighborhood, the appearance of the coop design in this case was just as important as being sturdy and predator proof.

After getting the green light from the neighbors on a shaded spot nestled just inside the wooded area at the back of their property, the Rogers’ fell in love with the charm of the 4’x8’ Playhouse Coop design, and selected a charcoal gray metal roof, and red cedar colored stain for the exterior walls.  

Rogers Family's 4'x8' Playhouse Coop from Microfarm Organic Gardens on Vimeo.

The framing of the coop is made with red cedar and wrapped with ½ hardware cloth, and the siding is made from sheets of rough sanded cedar T1-11 plywood. We use Timber Pro UV non toxic stains and sealers for our garden projects.

In order to extend the life of the coop and discourage digging predators, we placed it on a base made of 2”x8”x16” concrete blocks.

The Playhouse Coop’s design is large enough to house up to 5 hens and has a human entry door for easy access to clean the coop and top off food & water. Features like the standing seam metal roof panels, all cedar construction, and roost box window and flower box put the design  right at home in even the most upscale backyard setting.

Macronutrients and Micronutrients for Plants

While most gardeners know that all plants require varying amounts of the elements which comprise the three Primary Macronutrients  - Nitrogen, Phosphorous, and Potassium - to live a healthy life, the importance of elements classified as secondary macronutrients and micronutrients can be news to even veteran growers.  You may not have realized that calcium, molybdenum and boron are useful to plants in small amounts, but chances are you’ve seen the results of a deficiency in these elements. Strange coloration, stunted growth, and multiple buds in plants can be signs that the soil is lacking in essential macronutrients  and micronutrients.

PRIMARY MACRONUTRIENTS

Nitrogen : Used most out of the three primary macronutrients, nitrogen is the major constituent in chlorophyll and necessary  to encourage strong vegetative growth.

Phosphorous : The second most important primary macronutrient, phosphorous is used for the development of fruits/flowers.

Potassium :Potassium is the third most important primary macronutrient, and typically occurs naturally in the soil. The potassium salts that are necessary for plant cell functioning are referred to as potash.

SECONDARY MACRONUTRIENTS

Calcium : Buffers the soil pH, making it more alkaline, and helps rootlets absorb soil nutrients

Magnesium :  Enzyme activator, and the central element in the chlorophyll molecule

Sulfur : Found in amino acids that make up plant proteins, and activates certain enzyme systems.

MICRONUTRIENTS

Copper :  important for reproduction

Manganese : Works with plant enzymes to help break down carbohydrates and metabolize nitrogen

Iron : Essential for the formation of chlorophyll

Zinc : Regulates consumption of sugar in the plant

Boron : Aids production of sugar and carbohydrates, chlorophyll synthesis

Molybdenum :  Helps the plant capture nitrogen

Chlorine : Required for photosynthesis