Balcony vegetable gardening: techniques and suitable varieties

Growing on a balcony is not a scaled-down version of a vegetable garden: it is a different exercise, with its own constraints. The main one is neither space nor light, but the volume of substrate. In the ground, a plant explores, compensates, and seeks out water and minerals wherever they are. In a pot, it has strictly only what you have provided—and when that reserve is exhausted, there is no fallback.

Everything that follows stems from this constraint: size the container generously, compose a substrate that will last the season, water accordingly, and choose species that can cope with limited volume.

Sizing the containers

This is the most consequential decision, and the one where optimism most often leads us astray. A pot that is too small dooms the crop from the outset: no amount of care can make up for insufficient volume.

Three details that make all the difference

• Drainage holes, always. A container without drainage turns the bottom into an anaerobic zone where roots rot. If you repurpose an object, drill holes in it.
• A light color is preferable. A black pot in full southern sun can exceed 40 °C at root level, a temperature at which roots stop functioning and then become damaged. A light terracotta pot, or simply shading it with another pot, solves the problem.
• A saucer in summer only. It provides a small reserve that is useful during hot weather, but in winter it drowns the roots and increases the risk of freezing.

With the same volume, a wide, shallow pot dries out much faster than a narrow, deep pot: less exposed surface means less evaporation. The extra depth also allows roots to grow down to where the substrate stays cool.

The substrate: a miniature living soil

A store-bought potting mix used on its own runs out in two months and compacts: its structure relies on fibers that decompose, and nothing replaces them. A mix that lasts the season:

• 60% quality potting soil for vegetables — the base
• 20% mature compost — the fertility reserve and, above all, the microbial life that will make it available
• 20% drainage material — coco coir, perlite, fine pumice, or coarse sand

Some people add a small amount of clay (bentonite) to improve water retention: it works effectively when used in moderation.

Mulch your pots too

This is the most rewarding thing you can do on a balcony, and almost no one does it. Two centimeters of hemp, flax, cocoa shells, or simply dry leaves significantly reduce evaporation, prevent the substrate from crusting over on the surface, and buffer temperature fluctuations.

Maintaining fertility

A pot has no reserves: nutrients are carried away with the drainage water. Add compost or vermicompost every six to eight weeks for heavy-feeding crops (tomatoes, zucchini, peppers), and less often for Mediterranean herbs, which prefer lean conditions. An apartment worm composter closes the loop: kitchen waste goes back into the pots.

What to grow according to exposure

Full south-facing exposure, 6 hours of sunlight or more

Everything is possible, but the constraint becomes thermal rather than light-related. Favor cherry tomatoes, peppers, hot peppers, eggplants, and Mediterranean herbs — thyme, oregano, savory — which thrive in relatively dry, poor substrates. Provide light shade during the hottest hours in July and August.

East- or west-facing, 4 to 6 hours of sunlight

In reality, this is the best exposure for a balcony vegetable garden: morning or evening sun, with much less water stress. Lettuces, Swiss chard, radishes, dwarf beans, strawberries, basil, and zucchini in a large container.

North-facing or shade, less than 4 hours

A challenging situation, but not a barren one. Parsley, chives, mint, sorrel, lamb’s lettuce, spinach, arugula, and summer lettuces that bolt much more slowly in the shade. However, give up on fruiting vegetables: without sufficient light, they produce leaves rather than a harvest, and you will lose a season hoping.

Make use of vertical space

A 3 m² balcony often provides 6 m² of wall space. Trellises for sweet peas and climbing beans, tiered shelves to prevent the pots from shading one another, wall pockets for herbs, hanging baskets for trailing cherry tomatoes and nasturtiums.

Watch the weight. A 40 L container filled with wet soil weighs around thirty kilos. On an older balcony, distribute the load along the load-bearing wall rather than at the edge, and check the maximum permitted load if in doubt.

Watering: the real challenge

This is what causes most balcony vegetable gardens to fail, in both directions: too little water kills quickly, while too much kills slowly but surely by suffocating the roots.

• Test with your finger to a depth of 3 cm before each watering. A dark growing medium at the surface may be dry underneath, while a light-colored medium may still be wet. The weight of the lifted pot is another good indicator.
• Water generously until water runs out through the holes, then let the soil partially dry before watering again. Small, frequent amounts only wet the top of the pot and keep the roots near the surface.
• Early in the morning or in the evening, never in full sun on the foliage.
• A completely dried-out growing medium becomes hydrophobic: it shrinks, water runs down the sides and out through the holes without moistening the root ball. In that case, immerse the pot in a basin for twenty minutes, until the bubbles stop.
• Plan for absences. In July, a tomato in a 20 L pot drinks every day. Group the pots in the shade before leaving, double the mulch, or install a timer-controlled drip irrigation system — the most reliable solution for absences lasting more than three days.

Wind: an underestimated challenge

At height, wind dries things out faster than the sun and breaks stems. An openwork windbreak — reed screening, trellis, row of sturdy plants — is much more effective than a solid wall, which creates turbulence behind it and can make the problem worse. Always stake fruiting vegetables, even dwarf varieties, and choose heavy or weighted containers on upper floors.

Frequently asked questions

Can potting soil be reused from one year to the next?

Yes, provided you revitalize it: remove the roots and large debris, then mix it with one-third fresh compost and a little drainage material. Replace the substrate completely if there has been a root disease, and avoid planting the same botanical family in the same pot two years in a row — crop rotation applies to containers too.

Are clay pebbles needed at the bottom?

Contrary to common practice, it is not always useful. A drainage layer at the bottom creates a change in texture that can hold water just above it, exactly where you wanted to avoid it. A properly well-draining substrate and good drainage holes are usually sufficient; a layer of clay pebbles is still useful in very deep containers or those without side drainage holes.

What should you do in winter?

Corn salad, spinach, arugula, and perennial herbs can stay outdoors without any problem. Two precautions: group the pots against a wall, and remember that roots freeze much faster in pots than in the ground — it is the container that needs to be wrapped in winter fleece or cardboard, not just the foliage.

Do balcony-grown vegetables have less flavor?

No, provided fertility and watering are adequate. Slight water stress can even concentrate flavors, especially in tomatoes — but if repeated, it greatly reduces yield and causes the fruit to split.

Can you harvest your own seeds on a balcony?

Yes, and it is even simpler than in the garden for self-pollinating species: fewer varieties nearby means fewer crosses. Tomatoes, beans, lettuce, and basil are particularly well suited to this. See How to save your seeds.

Key points

Choose larger containers, mulch your pots, and start with three or four carefully selected species rather than ten struggling ones. A well-managed balcony can produce all the herbs needed for a kitchen, plus enough to accompany summer meals — which is already quite an achievement in three square metres.

Further reading

• Creating a permaculture garden in a small space
• The month-by-month sowing calendar
• Basil seeds: sowing and companion planting
• Heirloom tomato seeds: varieties, sowing, and care

Our year-round sowings and our culinary and medicinal herb seeds, particularly well suited to growing in pots.