This is one for the serious rooftop gardener; it’s about as far away as possible from hanging a few window boxes outside. Urban food farming doesn’t get much more ambitious than creating an edible forest on a roof; you’ll need the input of a landscaper, not to mention a structural engineer, but what rewards! And what inspiration, even for the small-scale balcony gardener—you can be sitting in the middle of a town but lost in a woodland wonderland, idly wandering the paths and picking cherries. It’s incredible that 10 ft. trees can grow in just 1 ft. of soil, but prepare it right and you can create a fully grown edible forest.
Inspiration STAIRWAY TO A HAVEN
Nowhere is this urban farming model more inspirational than at the Reading International Solidarity Center garden in the south of England. There, the rooftop oasis leads you on a world tour of bizarre and beautiful edibles; from Chilean guava to medlars, Japanese wineberries, shiitake mushrooms, and crunchy oca tubers. There are mature cherries, cobnuts, pears, and apples, but other less obvious edible trees, too, all with food or medicinal uses. Willy Wonka-style blue beanpods hang from the blue sausage fruit tree (Decaisnea fargesii), clusters of weird pink spiky balls adorn the strawberry tree, and the toothache tree (Zanthoxylum alatum planispinum) is sprinkled with vivid red, peppercorn-like berries that, when chewed, fill your mouth with spices. Elsewhere a Juneberry tree, dotted with tiny, sweet, red berries, nestles next to the broad, exotically glossy canopy of a loquat.
The fences and walls of this garden are thick with vines—grapes, kiwis, hops— and canes of wineberries and raspberries. Along the sides of the woodland-style paths, mulched with woodchips and shingle, grow wild garlic, wasabi, Solomon’s seal, sorrel, and wild strawberries from the regular woodland variety to the bizarre hairy fruits of the Plymouth strawberry. In fall, a fat windfall medlar fruit lies on the forest floor, its flesh pulpy and sweet. Everywhere you look a plant reveals itself to be intriguing and extraordinary—if not always at first sight, then at first taste—such as with stevia, the super-sweet leaf once commonly used as a sugar, or the exquisite wild-strawberry-flavored berries of the Chilean guava bush.
Solar panels and a wind turbine power a pump for a rainwater storage system, materials are recycled, waste food from the café downstairs is composted, and animal life is encouraged with strategically placed nesting boxes and piles of logs. A thick layer of mulch retains moisture in the soil and keeps down weeds, while sprawling strawberries and herbs do the same job.
This is not just a roof garden, it’s a roof forest: a living, breathing, self-sustaining ecosystem that mimics the multiple layers of vegetation found in the wild—fruit and nut trees are underplanted with berry fruits that grow in their dappled shade, and beneath them are herbs and low-lying vegetables and fruit. Unlike traditional fruit and vegetable gardens, where many crops are replaced each year with new seedlings, these edible forest plants will live for several years, producing fruit, leaves, and nuts. This is a low-maintenance, more natural model of food production—permaculture in the sky.
STEAL THEIR STYLE: CREATE A MINI EDIBLE FOREST
An edible roof garden such as this one is surprisingly low-maintenance since most of the crops are perennial. Berries, vines, and fruit trees once planted will last for years, requiring only a little pruning and giving lots of fruit in return. Herbs such as thyme and mint are similarly long-lived, as are strawberries and sorrel. All grow easily in pots and require less effort than annual crops—none of that fiddling with seedlings every spring.
Try to be sustainable, storing rainwater whenever you can—in rain barrels or even buckets. Consider keeping a wormery to turn your kitchen scraps into compost. Mulch containers with anything that will help keep moisture in the soil. When planting, try to combine crops so that they can benefit from each other, underplanting climbers and shrubs with groundcovering perennials that can shade and retain moisture in their roots—a hardy kiwi, for example, underplanted with wild strawberries.
Project : MAKE A LOW-TECH WATERING SYSTEM
You don’t need an automatic watering system. A collection of containers or a raised bed will really benefit from the gradual drip-drip from a seep hose fed by a bucket raised on bricks. All of the necessary items are available in garden or home improvement stores. You will need
- A household drill
- 1 sturdy bucket
- A plastic tap (such as those for rain barrels)
- 4 or 5 bricks (or similar) to stand the bucket on
- A length of seep or soaker hosing, perforated or garden hose with holes made in the side
- 1 plug or stopper for the end of the hose
How to do it
Drill a hole in the side of the bucket near the bottom and push the tap into it so that it fits snugly. Stand it on the bricks, then attach the hose to the tap and lay the hose on the soil surface, weaving it around your plants. Put the plug in the open end of the hose. Fill the bucket with water. Slowly, the water will seep out of the holes in the hose into the soil around the plants roots just where they need it, making your watering less frequent and less complicated. The bucket will catch rainwater too.
Classic edible-forest roof crops, working from the canopy down
- Tall crops: Apples, pears, plums, cherries, quinces, olives, peaches, apricots, figs, strawberry trees (Arbutus andrachne), loquats, cobnuts, mulberries, Juneberries
- Scrambling vines and sprawling canes: Grapes, hardy kiwis (Actinidia arguta ‘Issai’), raspberries, Japanese wineberries (Rubus phoenicolasius), edible passionflowers (Passiflora edulis), loganberries, blackberries, marionberries, boysenberries
- Shrubs: Blueberries, Chilean guavas, Goji berries, gooseberries, cranberries, jostaberry
- Medium plants: Lemon verbena, rosemary, sage, lavender, valerian, mint, sorrel
- Ground cover: Wild (woodland) strawberry, oca (Oxalis tuberosa), sorrel, garlic chives, chives, wild garlic, lemon balm, thyme, oregano, wasabi, Plymouth strawberries
The top 5 unusual crops for an edible forest roof
These are vines, so they will climb up supports and make quite impressive plants with a really jungly feel. In cooler climates, choose a hardy kiwi (Actinidia arguta), such as ‘Issai,’ which produces bunches of deliciously sweet, grape-sized fruit that you eat with the skins on (they’re not hairy like regular kiwis). They can survive extremely cold winters and, if pruned properly, produce a good crop. For regular-sized fruits try Actinidia deliciosa, but make sure you plant both a male, such as ‘Tomuri,’ and a female, such as ‘Vincent.’
Plant kiwi fruits in a large pot at least 1 ft. in diameter filled with soilless potting mix or loam-based potting mix and place in a sheltered, sunny position, protecting young shoots from frost in early spring. Without pruning, the vine will clamber all over the place and produce few fruits, so it’s well worth keeping it in check.
Fix parallel wires to a wall about 18 in. apart or provide a trellis for the vine to climb up. Push a long bamboo cane into the pot and tie it to the wall supports. When the vine reaches the bottom support wire, rub out all but three shoots, tying the uppermost one to the cane and the others to the horizontal wire on each side of the main stem. These side shoots are now called “laterals.”
When the vine reaches the second wire (or grows about another 18 in., if using a trellis), tie in two further side shoots to the wire, rubbing out any other new ones, to form two further laterals. Prune the laterals when they are about 3 ft. long to encourage side shoots to form along their length. As the plant continues to grow, pinch these side shoots back to five leaves—it’s from these side shoots that fruiting spurs will develop. In the winter, prune back the side shoots to two buds beyond where the fruit bloomed the previous summer.
Alternatively, if you want a more jungly look to your vine, and fruit production is less of a priority, cut out flowered stems in spring to allow the new stems space to grow and develop.
Even in winter, this relative of the raspberry, Rubus phoenicolasius, makes a stunning sight and a real talking point, with its brilliant pink stems covered in orange hairy spines. In winter sunlight the spines are breathtaking. Its small orange-red berries are succulent and sweeter than raspberries.
Grow it as you would a raspberry plant, planting it in a large pot at least 18 in. in diameter and cutting down fruited canes to the ground in late summer, then tying in strong new canes to wires attached to the wall. If you tie the stems into a fan shape the plant looks pretty all year round. Alternatively, grow it in a freestanding pot—the stems will droop artistically.
A “superfood” with 500 times the amount of vitamin C by weight as oranges, goji plants (Lycium barbarum) are shrubby bushes with bright red, rosehip-like berries. Native to the Himalayas, they are known there as ‘happy berries’ because of the feeling of well-being they are said to induce when eaten.
Plant in full sun in a large container at least 1 ft. in diameter. The plants grow fast, reaching up to 4 ft. tall in a pot, and can produce 2 lb. of fruit in their second year. Wind- and drought-tolerant, they are easygoing plants and excellent for a rooftop. Eat the berries fresh and enjoy the licorice taste, or try them dried, when they taste a little like cranberries—you can dry them yourself and add them to cereal for a powerpacked start to the day.
This unusual tuber (Oxalis tuberosa) from South America looks a bit like a small potato or a Chinese artichoke. You can boil or roast oca, but it is best eaten raw, when it has a lovely fresh crunch and a lemony taste. Plant it from late spring, when the danger of frost has passed, in containers about 8 in. apart. The leaves will sprawl everywhere, though you can tie them to an upright support to keep them tidy.
The most unusual thing about oca is that you don’t harvest the crop until late fall, even early winter, after the frosts. Even if the foliage is frosted and dead, the tubers will still keep growing underground. Leave a few tubers in the pot when you harvest them and you will have more next year.
An evergreen shrub from the myrtle family, this looks a bit like a box bush but has the bonus of wonderful berries that ripen in the fall. Reputedly Queen Victoria’s favorite fruit, these red berries taste rather like a spicy strawberry, or strawberry Space Dust —that explosive, sherbety childhood sweet of years ago.
Plant young plants in acid potting mix in a medium container (they like to feel snug around the roots) positioned in sun or partial shade, and feed only once a year in spring with garden potting mix, well-rotted manure, or liquid seaweed. Harvest the berries in late fall. A row of these bushes would make a good evergreen hedge to block out neighbors.