Anywhere there is light and space plants will grow - you dont need to have a lot of space to create a micro edible landscape. With a little ingenuity and imagination, window sills, balconies and many rooftops can be adapted to provide a good proportion of vegetable needs for a household. Robyn Francis explores the productive potential of container gardens and tips for the potty gardener.
One of the most intensive gardens I've encountered in my travels was on a roof top in Manhattan. A tiny penthouse apartment opened onto a 3x3.6m (10'x12') area of rooftop above the 38th floor. This small space was absolutely crammed full of every recyclable household container imaginable; milk cartons, cans, plastic bottles, cracked bowls and coffee mugs and several old boots all filled with compost growing a multitude of herbs and vegetables. The compost was made on-site from kitchen scraps processed by earthworms in a 20 litre (4 gallon) drum. The couple living there didn't need to buy any fresh greens and were justifiably proud of their mini food jungle.
In Cuba I saw many more inspiring rooftop and courtyard container gardens in Havana and several provincial cities. Many of Cuba’s famous ‘Organiponicos’, organic urban market gardens, are actually large container gardens made using lengths of old cement pipes (half rounds) or tubs filled with compost growing an abundance of fresh food. Some organiponicos are established on top of the bitumen in former carparks, and is a model that can be adapted for large-scale rooftop production in high rise urban environments.
With a little ingenuity and imagination, window sills, balconies, small coutyards and many rooftops can be adapted to provide a good proportion of vegetable needs for a household. First there's a few important things to consider before creating your container micro eden.
Sun, shade and wind are major constraints on balconies and these factors will change with the seasons. Neighbouring buildings can create wind tunnels and turbulence and may effect sun/shade patterns throughout the day. A lattice trellis along the windward side of a rooftop provides a windbreak without creating turbulence as a solid break tends to, and provide an opportunity for climbing plants. The photo (right) is a rooftop garden in Havana protected from afternoon sun and westerly winds by a wire trellis supporting a productive grapevine.
Load bearing capacity of balconies and rooftops. Balconies are usually built to support only a few people, so it is important to consider how much extra weight it can support. Weight is also important for roof top gardens. Remember that one cubic metre (10 cubic feet) of soil weighs about one tonne. This can be remedied by using lighter soil mixes and by making sure that drainage is adequate for the removal of excess moisture. Plastic pots, are lighter than ceramic or concrete pots, so choice of container will also have weight implicationsl. Recycled styrofoam fruit boxes make excellent containers since they are light, insulate the soil against excessive heat and provide a good root area for growing many vegetables. Place the larger and heaviest containers where there is the most architectural support.
Probably more important than direct sun is natural light. If insufficient natural light is available the plants will grow tall and weak stretching towards the most convenient light source. Mirrors or reflective surfaces will increase light or you can make a mobile garden on a trolley that can be wheeled around to catch the best light or a few hours of sunshine.
Soil mix needs to drain well to reduce problems with waterlogging, fungal disease and increased weight. On the other hand a soil mix that dries out too fast and doesn't retain moisture will impair healthy plant growth and encourage ants. Drainage is also important after the water leaves the pot. The neighbour below may not appreciate a waterfall or drips onto their balcony. A shallow container under a pot will reduce run off problems and the water collected there can soak or wick back up into the potting mix. A few small holes in a recycled plastic bottle filled with water will provide a slow drip system for larger pots and tubs.
Container gardens do need special care regarding water and nutrients since in the restricted environment of a pot, roots can't burrow deep down into the soil to tap into the earth's natural supplies. Watering systems can vary from a watering can through to trickle irrigation system or a garden hose connected to the kitchen tap. Some fine mulch, small stones or gravel around the base of plants in pots will help retain water and keep the potting mix moist but avoid building mulch up against the stem of the plant as that can encourage fungal problems.
If pots dry out the soil mix can become hyrophobic, that is so dry that it repels water, and the dehydration shrinks the mix away from the edge of the pot. Then when you water your wilting plants you'll notice the water runs down the inside edge and straight out the holes in the bottom and most of the soil mix is still bone dry if you scratch down a few millimeters. The soil can be rehydrated by standing it in a container of water to at least half the depth of the dry pot for 15 minutes or so. For dried out larger pots too big to soak in a bucket, give lots of small waterings and put a few slow-drip plastic bottles on to give the soil time to reabsorb moisture.
Potting mixes vary, however most lack sufficient nutrients to sustain healthy growth of productive plants. Some nutrients will be available in a potting mix containing compost, manure or earthworm castings and these nutrient rich materials can be added to commercial potting mixes. It’s generally recommended to add no more than 10% worm castings or 10-20% compost to a potting mix. Organic liquid fertilisers such as worm juice, fish emulsion, kelp (seaweed) extract or compost and weed 'teas' can provide an important source of nutrients for container gardens. Liquid fertilisers and 'teas' should well diluted and make sure the soil is moist when you apply them. Where these are providing most of the nutrient needs for bearing or maturing plants a weekly application may be necessary.
A bokashi system is ideal for urban dwellers with no yard for compost making. A bokashi units can sit on a kitchen shelf and turn you food wastes into a high quality organic fertiliser for your container garden
A small amount of biochar (10-20%) in potting mix will improve drainage as well as nutrient and moisture retention. Some heavy calcium feeders or plants preferring alkaline soils (tomato, cabbage family, herbs) may also require light dressings of garden lime or dolomite, or you can try adding finely crushed eggshells into the mix.
There are a number of ways to maximise limited space. When potted plants are placed close together, as the plants grow they can compete for space and light resulting in over-crowding. This problem can be avoided by arranging pots of different heights, stacking, shelving, hanging or terracing the pots, to provide plants sufficient horizontal space to grow to maturity. Vegetables that grow well in hanging pots or baskets include 'Tiny Tim' tomato and small cucumber varieties, which will cascade down for convenient harvest. Nasturiums are also great in hanging basket and you can eat the flowers and leaves in salads.
A table or cupboard placed under a window sill will provide space for extra pots. Climbing plants can scramble along balustrades and railings or you can suspend wire, rope or other trellis supports around windows and glass doors as a 'green frame'.
Many herbs can be grown in shallower pots or used as space fillers in larger tubs or in hanging baskets. Vegetables will need more root space and should be grown according to season. You can get several crops from one pot, for example when you plant a small sweet pepper (capsicum) or chard (silver beet) seedling, which takes some time to grow and bear, you can sow a few small radish, corn salad or cress seeds around it which will be ready to harvest in a few weeks while the larger plant is establishing.
Companion planting combinations can be used in larger containers such as styrofoam fruit boxes or tubs. A row of climbing beans can be planted along the back to climb up a trellis with a broccoli in the centre and a parsley plant in each of the front corners, or a tomato can be grown with a basil bush and several parsley.
Some fruit trees suitable for growing in large tubs include pomegranate, cherry guava, fig, mulberry, kumquat, lime, mandarin, and any dwarf fruit varieties e.g. peach, apple, nectarine, persimmon. Some herbs will enjoy growing around the base of the tree, particularly chives, chervil, garden cress and nasturtiums. Dwarf fruit trees in pots can be espaliered along walls or balcony balustrades and railings. Berry bushes including Cape & English gooseberry, blueberry, black & red currants will also bear well in containers.
On rooftops there are a number of options in addition to container gardens. Raised garden beds can be constructed provided there is a layer of drainage material under the compost or soil. The use of gravel for drainage is often limiting due to the weight so lighter materials such as recycled styrofoam or 'bean bag' pellets can be used or lightweight commercial materials designed for drainage e.g. Geofabric Bidim. Of course garden structures such as pergolas, shade houses and greenhouses may also be included in a roof top design.
In Berlin I visited several apartment buildings with roof top 'community gardens' and greenhouses. Some included areas of hardy turf for recreation and to provide insulation for the building below.
Office buildings can also be productive environments, especially when you consider all the window space that can receive sunshine. If you look at an office block as a vertical greenhouse, the imagination can run riot. Instead of all those ornamental hire plants that frequently adorn offices there could be bumper crops of herbs, vegetables and fresh fruits. Grow your lunch in the office and enjoy eating it on the rooftop under the shade of a grape smothered pergola!
With a limited space to grow food, I advise concentrating on vegetables and herbs that produce quickly and are conducive to continuous harvest rather than slow growing one-time harvest crops like cabbage or corn. Leafy greens are some of the best value for effort, not only in terms of yield for space and short growing time, but they lose nutrients and quality rapidly post-harvest and are best used as soon after harvest as possible.
Salad greens such as non-hearting lettuce like oak-leaf, lollo rosso and curly leaf lettuce do exceptionally well, as do rocket, parsley and mizuna. Silverbeet and chards, kale and Warrigal greens (New Zealand spinach) are also good value and can bear for many months, even a year or two but usually require a slightly larger container for more root growth to sustain production. Other long-bearing vegetables include climbing beans, snow peas, tomatoes, capsicum (sweet pepper), zucching, button squash and cucumber, all of which do best in container holding at least 3-4 liters of soil mix to support their root system.
Most culinary herbs grow well in containers, especially classics like chives, thymes, marjoram, oregano, winter savory, sage, basil, coriander and rosemary. And dont forget to grow some edible flowers to colour up your micro eden. Flowering plants also attract beneficial insects like bugs that eat the bugs that eat your plants.
All living plants, edible or not, are very important in the artificial environment of the city. They filter out many pollutants and produce negative ions which are essential for human well being. The excess of positive ions common to dense urban and inner city environments will contribute to stress symptoms, irritability and headaches, so having lots of plants around you helps ameliorate this.
If you’ve no windowsill, balcony or rooftop to grow things you can always find a community garden to get involved in, or try your hand at some clandestine guerrilla gardening.
Robyn Francis, November 2010
This article includes extracts from the booklet, Micro Eden: Urban & Small Space Permaculture Gardens by Robyn Francis
Robyn Francis, international Permaculture teacher and design consultant since 1983, was founder of Permaculture International, Permaculture College Australia Inc and Djanbung Gardens Permaculture. Her work has involved everything from farm and garden design, to ecovillage and regional transition planning. An organic gardener for over 40 years she continues to grow most of her own food on her Permaculture farm in Northern NSW.
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