Lesson 4
Vertical gardens and green walls
Vertical gardens are irrigation nightmares unless you plan properly. Water runs down; plants at the top dry out while those at the bottom drown. Pockets drain fast. Wind accelerates evaporation. A felt-pocket wall garden in full sun can need water twice a day.
The only sustainable solution is an integrated drip system. Most modular wall-garden kits — VertiGarden, Verti-Plant, Burgon & Ball — include a drip line that runs along the top with emitters feeding each pocket. Connect it to a timer and run it for 5–10 minutes twice daily in summer. Check the bottom pockets weekly; if they are waterlogged, reduce the duration or add drainage holes.
For DIY systems or older setups without built-in irrigation, retrofit a drip line by clipping 4mm micro-tubing along the top rail with inline emitters positioned above each pocket. Use pressure-compensating emitters so every pocket gets the same flow regardless of height. Expect to spend £30–50 on tubing, emitters and a splitter manifold.
Choose plants carefully. Shallow-rooted herbs and salads — thyme, oregano, lettuce, rocket — cope better with the limited soil volume than deep-rooted crops. Strawberries are ideal. Trailing tomatoes work if you feed weekly. Avoid anything that resents root restriction: beans, courgettes, full-size tomatoes.
Common mistakes
- Planting top-heavy crops that exhaust the compost in weeks
- Running irrigation once a day for 20 minutes — top pockets flood, bottom ones silt up
- Forgetting that walls radiate heat — south-facing walls can be 5°C hotter than ambient
- Using garden soil instead of a lightweight, moisture-retentive mix designed for vertical growing
- Not checking the bottom pockets for drainage — stagnant water kills roots fast
What thrives in vertical pockets
- Herbs: thyme, oregano, marjoram, chives, parsley, coriander
- Salads: cut-and-come-again lettuce, rocket, mizuna, land cress
- Strawberries: especially compact varieties like Flamenco, Toscana, Mara des Bois
- Edible flowers: nasturtiums, violas, calendula, borage
- Trailing veg: tumbling tomatoes (Tumbling Tom, Hundreds & Thousands), alpine strawberries
Mount vertical gardens at least 5cm proud of the wall to allow airflow behind — trapped moisture against brickwork invites slugs and mould.