Raised Bed Gardening in Small Spaces: Building and Planting on Balconies and Terraces

Why Raised Beds Beat Individual Pots

A single 1 x 2 meter raised bed on a balcony gives you 2 square meters of planting area — equivalent to 12–15 individual 30 cm pots, but with several advantages. The continuous soil volume lets roots spread without restriction, eliminates the constant watering that individual pots require, and creates a stable soil ecosystem that improves over years. You also get more food per square meter, because plants can be spaced more efficiently in a continuous bed than in separate containers.

Raised beds are particularly valuable for root crops (carrots, beets, radishes, potatoes) that need 25+ cm of loose, well-drained soil — much more than most pots provide. They also make gardening physically easier, since you can sit on the edge of the bed to plant, weed, and harvest rather than bending to ground level. For older gardeners or anyone with mobility limitations, a raised bed at waist height (60–80 cm tall) is transformative.

Choosing the Right Size and Depth

The ideal raised bed width is 1 meter — narrow enough that you can reach the center from either side without stepping on the soil. Length is flexible and usually limited by available space. Depth matters more for what you can grow: 15 cm is enough for shallow-rooted greens (lettuce, spinach, herbs); 25 cm supports most vegetables (peppers, bush beans, carrots); 40+ cm is needed for deep-rooted crops (tomatoes, parsnips, leeks) and perennials.

If you are building the bed on a balcony, depth is also a weight trade-off. A 1 x 2 x 0.4 m bed holds 800 liters of soil — about 500 kg of dry mix or 700 kg wet. Reducing depth to 0.25 m cuts the weight to 500 kg wet, which is much more manageable. You can also create 'variable depth' beds that are deeper at one end (for tomatoes and root crops) and shallower at the other (for herbs and greens).

Recommended bed depths by crop type:

• 15 cm — lettuce, spinach, arugula, most herbs, radishes, green onions
• 20 cm — bush beans, beets, carrots (short varieties), strawberries
• 25 cm — peppers, eggplants, peas, kale, chard, full-size carrots
• 30 cm — determinate tomatoes, summer squash, cucumbers (with trellis)
• 40+ cm — indeterminate tomatoes, asparagus, perennial herbs (rosemary, sage)

Lightweight Soil Mix for Balcony Beds

Standard garden soil is too heavy and dense for balcony raised beds. Use a lightweight mix designed for container growing — the classic 'Mel's Mix' from Square Foot Gardening is a good starting point: 1/3 compost, 1/3 peat moss or coco coir, 1/3 vermiculite or perlite, by volume. This mix weighs about 600 kg per cubic meter wet, compared to 1,200+ kg for garden soil.

Replace peat moss with coco coir for an environmentally preferable alternative — coir is a byproduct of coconut processing and does not involve the destruction of peat bogs. Use coarse vermiculite rather than perlite if you can find it, as vermiculite also holds moisture and provides trace minerals. Mix in a slow-release organic fertilizer at planting time and refresh with compost topdressing every 3–4 months.

Drainage and Waterproofing

A balcony raised bed must drain freely without leaking onto the balcony surface or the neighbors below. Line the bed with a permeable landscape fabric (not plastic, which traps water) and add a 5 cm layer of perlite or coarse gravel at the bottom. Drill drainage holes every 30 cm along the bottom edge of any solid-sided bed, and elevate the bed 2–3 cm on small blocks to allow air circulation and drainage underneath.

For waterproofing, place a rubber pond liner or thick plastic sheet under the bed and curl it up the sides by 5 cm. This catches any drainage and directs it to one end where you can collect it or route it to a drain. Do not seal the bottom of the bed — the soil must drain freely. The goal is to catch any overflow, not to make the bed watertight.

Best Crops for Small Raised Beds

In a 1 x 2 meter raised bed, you can grow a surprising amount of food if you choose compact varieties and use vertical space. The most productive crops for small raised beds are those that produce continuously over a long season, rather than single-harvest crops like head lettuce or cabbage.

High-yield crops for small raised beds:

• Cherry tomatoes (indeterminate, trained on a trellis) — 5 plants in a 1x2m bed, 10+ kg fruit per season
• Bush beans — 12 plants in the same space, harvest over 6 weeks
• Swiss chard and kale — 8 plants, harvest outer leaves for months
• Leaf lettuce mix — cut-and-come-again harvesting, 4+ harvests from one planting
• Radishes (between slower crops) — 25 days from seed to harvest
• Strawberries — 12 plants in the same space, fruit from spring to autumn
• Herbs (basil, cilantro, dill) — fill gaps between larger plants

Succession Planting for Continuous Harvest

The key to productive small-space raised beds is succession planting — replacing each crop with another as soon as harvest finishes. In spring, plant radishes (25 days), then bush beans (60 days), then fall lettuce (50 days) in the same square meter. Three harvests from one section of bed, in a single growing season. Plan successions at planting time, not after harvest, so you have seedlings ready to transplant the moment a crop is removed.

Keep a simple garden journal noting what was planted where, when, and how it performed. This becomes invaluable the next season for rotation planning — moving plant families between beds prevents the buildup of soil-borne diseases and balances nutrient demands. A 4-year rotation (solanaceae → legumes → brassicas → alliums/root crops) is the gold standard but any rotation is better than none.