Growing veg on walls

Vertical take-off

Upright structures provide vital extra planting space in small gardens. The protective and heat-retentive properties of a south-facing wall are ideal for those plants from hotter climes. Alexandra Baulkwill experiments with growing techniques to bring on tasty crops.

My motivation for creating a vegetable wall was simple – a desire for fresh produce on a daily basis and a lack of planting space in the narrow garden of my terraced home.

As a backdrop to the patio, which serves as an outdoor space for entertaining, my rather ugly, but fortunately south-facing, brick wall lent itself to growing plants on and up. I attached timber supports and a wire mesh to the wall for climbing plants such as squashes and runner beans. Onto this framework I securely wired shiny, silver containers that started life as olive and plum-tomato tins. These were ideal for growing herbs and compact bush tomatoes.

What to grow?

The wall’s south-facing aspect presented an excellent opportunity to grow vegetables that often perform at their best with some protection, or need relatively long periods of high temperatures for the best flavours to develop. So tomatoes, aubergines and basil were top of the planting list.

It was clear that spaces on the wall would start opening up once harvesting had begun, so I tried to choose crops to fulfil certain growth characteristics. Quick-maturing crops, for example rocket, would mean that any spaces from cropping would be filled rapidly. Many cut-and-come-again crops, including a range of salad leaves, often yield two or more harvests from one sowing. To help hide my brick wall I also selected particular types of vegetable for their attractive, dense foliage among which fruits would develop, as with runner beans and aubergines.

Getting started

If space to grow-on seedlings with protection is limited, use the plug plants now offered by many of the seed companies. Aubergine ‘Mohican F1’, and tomatoes ‘Tumbling Tom Red’ and ‘Tumbling Tom Yellow’ were delivered to the doorstep in late April/early May, at the correct stage of growth for potting on.

Cucumber ‘Marketmore’, chilli pepper ‘Prairie Fire’ and squash ‘Tromboncino’ were all raised from seed in modules or 5–7.5cm (2–3in) pots in a propagator, germinating best at around 20–21°C (70°F). These were then potted on and hardened off when the last of the frosts had passed.

Other plants could be sown directly into the containers from which they would be harvested. I thinly sowed cut-and-come-again crops, such as rocket, coriander and mizuna, approximately 13mm (0.5in) apart across troughs 15cm (6in) deep.

For potting on, containers of a wide range of shapes, sizes and origins were used. At the base of the wall, galvanised dustbins and plastic crates gave planting depth and volume for runner bean ‘Painted Lady’, cucumbers, squash and aubergines. I found that plastic pots and tin cans were well suited for growing basil, parsley and spring onions. And non-porous containers were chosen to minimise the drying effects of wind and sun.

Practical design

As this wall of vegetables was also the backdrop to the patio, it was important for it to look attractive as well as crop heavily. I bore in mind the habits and eventual heights of the plants when planning the layout of the pots across the mesh. I found that the troughs, with their strong horizontal lines, helped to break up the space, while individual pots provided accents and filled gaps.

Practicalities as well as aesthetics also had to be considered. At 2.4m (8ft) in height and 2m (6.5ft) wide, the wall was tricky to crop and water near the top without using a stepladder. For convenience I placed longer-to-mature chilli peppers and tomatoes higher up the wall – but later discovered that in this position the compost is more subject to drying winds. More successfully, I put most of my cut-and-come-again crops where they could easily be reached, to encourage regular cropping with scissors.

The base of the wall provided the most shelter and was a natural heat pocket for cucumbers and aubergines, which prefer higher temperatures. Meanwhile, the shade cast by some of the bigger plants helped to cool less heat-tolerant plants, such as parsley.

Watering and feeding

It was a challenge to keep plants adequately supplied with water through the heat and drought of a hot, dry summer. Positioned on a wall in this way, the pots received little rainwater. Watering by hand, in the early morning and evening would be sufficient, but I installed an automated watering system to ensure a consistent supply. Pipes were fed behind the wire mesh and one or two nozzles inserted into each container. A battery-powered controller fitted onto an outdoor tap timed the watering. However, I still needed to check the pots occasionally to ensure individual plants were not over- or under-watered.

I used a liquid tomato feed from early June onwards, as fruit began to set on the plants.

Winners and losers

A surprising number of the ‘tender and tricky’ plants did well with limited attention. Aubergines and cucumbers produced such bountiful crops that they will definitely be used in future years.

The runner beans gave a small, rather tough crop. The extreme summer heat made growing them in containers more difficult. Squash ‘Tromboncino’ produced too few of its conspicuous, marrow-like, long fruits to justify the space it required.

I cropped vegetables into October, although the productivity of some had declined or stopped altogether by then. The wall’s productive season probably could have been extended – as shown by the survival of several unwatered lettuce plants right into February! Suitable crops, for example winter salads, winter radish and Oriental mustards, could produce a supply of leaves out of season.

As a colourful backdrop for barbecues, my vegetable wall provided interest, excitement and delicious fresh produce.

Produce for wall containers

The following were tried on the garden wall:

Good performers
Aubergine ‘Mohican' AGM
Basils ‘Minette’, ‘Siam Queen’ and ‘Sweet Genoese’
Chilli pepper ‘Prairie Fire’
Coriander
Cucumber ‘Marketmore’
Lettuces ‘Salad Bowl’ AGM and ‘Salad Bowl Red’ AGM
Oregano
Parsley ‘Curlina’
Rocket
Squash ‘Tromboncino’
Tomatoes ‘Tumbling Tom Red’ and ‘Tumbling Tom Yellow’

Disappointing performers
Climbing French bean ‘Violet Podded Stringless’
Nasturtium ‘African Queen’
Runner bean ‘Painted Lady’
Spring onion ‘Rossa Lunga di Firenze’

Attaching containers to the wall

Choosing the site

A south-facing wall will receive the full heat of the summer sun for most of the day, which has both benefits and limitations. Walls that are southwest- and west-facing will also be suitable for container vegetable growing.

Materials needed

Ensure the wall is sound and clean of debris before starting. Take the wall measurements and select mesh or trellis work that will be strong enough to support the chosen quantity of containers and wet compost. It should also allow plants either to climb or cling as they grow. Expanded metal was used in this instance, its galvanized finish producing a contemporary feel.
Fix 5x5cm (2x2in) timber batons at suitable intervals for securing the mesh. Batons hold the mesh away from the wall, allowing air to circulate and making space to tie in plants and attach containers.
Fix mesh to the timber frame with staples at regular intervals. This will produce an expanse of mesh covering the face of the wall. The structure is now ready for planting up.

Preparing containers

Almost anything can be used as a container. Old catering tins of tomatoes, oil and olives make decorative pots when their labelling is removed. The straight sides of tins also fix flat against the mesh, unlike the sloping sides of plastic pots, which helps prevent compost from being washed away. Drainage holes in the bottom of containers are essential and can easily be made with a drill.
Many types of tin have seams running down from top to bottom. Ideally, aim to place these against the mesh; drill two holes either side for the garden wire that will thread through and support the container. For extra security two more holes at the base of the tin can be made; these are useful when pots are positioned at the top of the wall, where they are more likely to catch the wind. If adding extra holes remember to thread the attaching wire through before adding compost.
A range of containers can be used at the base of the wall. Terracotta and plastic pots are ideal for most plants, while dustbins and swing bins give excellent depth and volume of compost in which to grow vegetables, such as runner beans, that require a root run of at least 40cm (16in).
Adequate drainage must be provided. A layer of polystyrene chips in the bottom 5–10cm (2–4in) of larger containers allows excess water to drain away freely and also reduces the amount of compost needed to fill the pot. A soil-based compost can be used where the container stands on the ground, as weight is not an issue.

Planting up

Containers to be fixed to the mesh should be filled with lightweight multi-purpose compost. Water-retentive gel can also be added at this stage.
The illustrated 10cm (4in) wide pot was planted with three plug plants of basil ‘Sweet Genoese’.
Allow a gap of at least 5cm (2in) above the surface of the compost and the rim of a straight-sided pot; with tapered pots leave 7.5cm (3in), as compost is more likely to wash out at an angle.
Position the container, and wire it to the mesh, creating hooks to hold the weight. Once attached, water regularly and apply a liquid tomato feed from mid-June onwards.