While perhaps not quite as prolifically productive as the previous list, the following crops are all well worth growing since the rewards, when they come, are a real treat. Bell peppers These are surprisingly hot-blooded plants that need the sunniest, most sheltered spot you have if the fruits are to ripen through to yellow and red, so in some ways they should be treated as exotics. It’s not unusual in a less-than-Mediterranean climate for a plant to produce only two or three peppers that are still resolutely green by autumn.
Sow seeds as you would for tomatoes in early spring inside on a sunny windowsill, transplanting them to pots, raised beds, large window boxes, or grow bags (three to a bag) outside only at the beginning of summer. Keep the plants well-watered and feed them weekly with a fertilizer such as liquid seaweed once the fruits have formed. The plants can get quite lanky, so prop them up with canes or tie in to supports if necessary.
Good varieties for containers include ‘Sweet Tangerine Dream’ and ‘Bush Belle.’
Eggplants make wonderfully exotic-looking plants for raised beds or pots, with incredibly sensual, violet flowers, furry leaves, and, of course, smooth, purple fruits that hang from the stems like dark, glossy treasure. In cool climates, however, they are not easy to get to ripen successfully, so opt for a dwarf mini variety such as ‘Fairy Tale,’ ‘Millionaire,’ ‘Purple Rain,’ or ‘Mini Bambino’ for the best results. Those gardening in warmer climates might want to choose from luscious ‘Burpee,’ ‘Long Purple,’ or ‘Black Beauty.’
Sow ¼ in. deep in early spring inside in small pots and then transplant outside to large pots or grow bags (two to each bag) in late spring/early summer and place in a sunny spot. Alternatively, buy plants in late spring and plant them straight out. Feed once the fruit is golf-ball-sized with a high-potash feed such as liquid seaweed. Harvest mini varieties when the fruits are 2-4 in. long. Eggplants are delicious cooked in ratatouille or barbecued on skewers with chunks of halloumi cheese and zucchini.
Denser and more flavorful than the watery, store-bought versions, homegrown cucumbers are really worth the effort. Mini varieties such as ‘Straight Eight’ or ‘Sugar Crunch’ are particularly good for containers, picked when they are only about 4 in. long and sliced lengthwise to add to refreshing drinks such as Pimm’s, or to homemade tzatziki or Greek salads.
Buy plants in late spring or sow seeds in mid-spring in 4 in. pots inside and transplant outside to containers at least 1 ft. in diameter or grow bags when all risk of frost is past. Pinch out the growing tip when the plant has five leaves, to encourage it to bush out, and then tie in shoots to a wigwam, trellis, or other support. Feed the plants, which look rather like a more delicate climbing zucchini, every two weeks with liquid seaweed or any other high-potash feed.
WINDY BUT WONDERFUL—AN EDIBLE OFFICE ROOF
The London skyline stretches out to the horizon, while below Regent’s Canal lies straight as a ruler and, from nearby King’s Cross station, Eurostar trains are speeding off to Paris. Geese fly by beside kale, chard, and cabbages growing in pretty, wovenwillow planters on four raised beds. Strawberries nestle under the snow, while the already-plump buds of gooseberries and black currants point to a good growing season ahead. By summer, the rooftop is alive with tomatoes, zucchini, greens, and bush beans. Feathery carrot tops peek out above the rim of a willow planter, while scratch the surface of the potting mix and you uncover the white treasure of ‘Anya’ potatoes. You’d never believe you were on top of a busy international brand consultancy, unless you saw the workers grazing the beds while taking a break, or helping out by planting a few seedlings.
Everywhere there are signs of sustainability on high. Four rain barrels store water gathered from a small, sloping roof—providing around 30 percent of the roof garden’s watering needs—and a wormery and potting mix bin process kitchen scraps and prunings which will eventually end up back in the soil as nutritious potting mix to feed future crops. The latter themselves end up in the staff restaurant downstairs. And so the cycle continues.
The crops clearly love the lavish sunshine the rooftop provides. However, careful measures have been taken to reduce the damaging effects of the frequent wind, so strong that garden furniture is chained to the railings to prevent it from sliding across the roof. Local regulations at this site do not allow windbreaks to be fixed to the railings, so the garden’s creators have had to improvise. The soil level in the planters is not only kept fairly low to give the crops the additional protection of the walls of the containers themselves, but the raised beds are edged in low, woven fencing. The surface of the potting mix is mulched with a thick layer of cocoa shells to protect against the drying effects of the wind.
As well as this, the choice of crops has been made with the wind very much in mind. Dwarf runner and bush beans are good here but there are no climbing varieties since these would soon be turned to ribbons. Low-lying strawberries, greens, and potatoes do well, while the sturdy raspberry canes and red currant bushes seem to shrug off the wind, gleaming with juicy, red berries. Rosemary and thyme are similarly unbothered, but there’s an absence of tall, lanky crops. Corn would last only minutes up here.
TOP CROPS FOR A WINDY BALCONY
- Herbs: bay, rosemary, thyme, sage, oregano, chives, parsley
- Bush and runner beans
- Bok choy
- Goji berries
- Red currants
STEAL THEIR STYLE: HOW TO COPE WITH A WINDY SITE
Balconies and roofs can be notoriously exposed and windy, thanks to a combination of lack of shelter and the funnelling of wind through chicanes of tall buildings. This is a potential problem for the gardener since wind not only can damage and stunt plants, but also quickly dries out the surface of the potting mix. Windbreaks of woven material such as bamboo, reed, or willow screens are often more effective than solid barriers since they filter the wind rather than push it up and over the other side in a turbulent gust. Well-placed evergreen shrubs, such as box, rosemary, elaeagnus, or grasses, or a trellis planted with climbing plants can also offer valuable protection.
If planting in raised beds, an additional low fence of woven willow or other screening around the edge will protect the crops within. If planting in pots, try keeping the level of potting mix fairly low to allow the pot sides to offer some protection and mulch all your pots or raised beds regularly with garden potting mix, cocoa shells, or an organic product such as composted straw to keep moisture from evaporating from the surface.
Steal their style: grow crops in a shallow raised bed
For those with medium to large balconies or roof terraces, a shallow raised bed around a yard square and 6 in. deep is a great way to maximize the crops you can grow. For those with small balconies there are also plenty of “mini raised beds” you can buy, which are generally lightweight, flexible bag planters that are perfect for getting the most out of a small space. Before adding any considerable raised beds, though, do check with a structural engineer if you’re at all worried about the strength of your balcony or roof. They may advise you to position the loads over certain points or tell you that the roof needs strengthening.
It’s fairly easy to nail together a raised bed using scaffolding boards or other planks, but, for ease, one of the many raised-bed kits available is a good choice. These are basically bottomless square or rectangular frames that can simply be laid down on the floor surface. Those made of plastic, such as Link-a-Bord, are ideal as they are lightweight and can be constructed in minutes without tools. They are also modular, so you can easily add a level to make them deeper, if weight allows, and you can buy additional insect mesh or fleece kits if you want to protect your crops from butterflies and the cold.
Before setting up your raised bed, check that your floor is well waterproofed and that it has a slight fall. All properly designed roofs and balconies, even “flat” ones, have a slight slope to allow rainwater to drain away. Make sure this path isn’t blocked so that water can run away. To increase the drainage properties of your raised bed even further, buy some wire-mesh panels (available from home improvement stores) and place them down on the floor under your raised bed. This raises the level of the potting mix a little, allowing water to drain away more easily. On top of the mesh, lay a porous woven membrane such as landscape fabric or weed-suppressing membrane (mini raised-bed kits may include this). This membrane will prevent potting mix from falling into the mesh and onto the roof surface, keeping the floor clean and protecting the roof.
Which potting mix is best for raised beds?
Since weight is likely to be an issue in a balcony garden it’s best to avoid loam-based potting mixes, as these are heavier. A good-quality soilless potting mix is a fine start, mulched with cocoa shells or bark mulch to retain as much moisture as possible. To maintain the fertility of the potting mix you will need to feed crops as they grow and add a thick layer of organic matter in the form of garden potting mix, spent mushroom potting mix, wormery casts, and/or well-rotted manure at least once a year. A good rule of thumb is to mix a trowelful of organic matter into the soil every time you remove a plant.
Which crops are best for raised beds?
Crops to grow in a 6-in.-deep bed:
- Lettuce and other greens
- Bush beans
- Runner beans
- Climbing pole beans
- Round-rooted carrots
- Onions, shallots
- Tumbling tomatoes
- Oriental greens such as mizuna, mibuna, tatsoi
- Basil, chives, cilantro, chervil, dill, oregano, mint, thyme
- Edible flowers such as nasturtiums, marigolds, violets
Crops to grow in a 8-in.-deep bed:
- Bush and vining tomatoes
- Fava beans
- Florence fennel
- Bell peppers
- Rosemary, sage, tarragon, parsley
Crops to grow in a 1-ft.-deep bed:
- Fruit trees
- Kiwi fruit
- Black currants
- Red and white currants