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The best containers for growing vegetables

Any safe container works if it is deep enough for the crop and has holes in the bottom. A bakery bucket with five holes drilled in it grows better spinach than a decorative pot with no drainage. Beginners often buy expensive pots that are too small and too shallow.

What can be a container

• Food-grade plastic buckets of 10 to 25 litres, which held icing, oil or yoghurt: for greens, tomatoes, chillies and herbs.
• Plastic crates lined with shade cloth or sacking: for lettuce, spinach, herbs and strawberries.
• Maize-meal sacks: for potatoes and sweet potatoes.
• Thick woven shopping bags and grow bags: for greens, herbs and potatoes. They dry out quickly.
• Clay pots: for herbs that like dry roots, such as rosemary and thyme.
• Bought plastic pots: choose deep ones in light colours, which stay cooler.

Depth matters most

A container that is too small dries out quickly, runs out of food and stunts the plant.

• Herbs, spring onions and lettuce: 15 to 20 cm deep, 5 to 10 litres.
• Swiss chard, spinach, kale and morogo: 20 to 25 cm deep, 15 to 20 litres, three plants each.
• Beetroot, radishes and short carrots: 25 to 30 cm deep.
• Chillies, peppers and brinjals: 25 to 30 cm deep, 15 to 20 litres, one plant each.
• Cherry tomatoes: 30 cm deep, 20 litres, one plant.
• Large tomatoes, cucumbers and butternut: 35 to 40 cm deep, 25 to 40 litres, one plant.
• Potatoes and sweet potatoes: 40 to 50 cm deep, in a sack of 40 to 50 litres.

A few larger containers are better than many small ones. They hold more water, stay cooler and need watering less often.

Drainage

Roots drown if water cannot get out.

• Make five or six holes about 1 cm wide in the bottom of a 20-litre bucket.
• Cover the holes with a piece of shade cloth or a flat stone, so that the mix does not wash out.
• Do not put a layer of stones in the bottom. It does not improve drainage, and it takes space from the roots.

Setting up

1. Raise the container on bricks, so that water drains freely.
2. Fill it with growing mix to about 3 cm below the rim.
3. Water the mix thoroughly and let it drain.
4. Plant, then mulch the surface.

Safe and unsafe containers

Food takes up what is in its growing mix.

Safe:

• food-grade buckets and tubs, washed well;
• plastics marked 2, 4 or 5 in the recycling triangle;
• clay pots and fabric grow bags;
• untreated wood, and pallets stamped HT (heat-treated);
• maize-meal and flour sacks.

Unsafe, however well washed:

• anything that held pesticides, paint, solvents, oil, fuel, pool chemicals or an unknown chemical;
• paint tins;
• greenish treated timber, creosoted wood, and pallets stamped MB or with no stamp;
• containers with flaking old paint.

Tyres are a special case. Rubber can slowly leach zinc and other substances into the soil. If you use tyres for food, line them with thick plastic so that the mix does not touch the rubber, and make drainage holes in the plastic.

On hard ground, build up

A keyhole garden is a round raised bed about 2 metres across and waist high, with a compost basket in the centre and a notch in one side so that you can reach it. Kitchen scraps and water go into the basket and feed the plants around it. It needs no digging and suits anyone who cannot bend easily.

A raised bed is a box of low walls about 1 metre wide, built on top of the ground. Lay cardboard on the bottom to smother weeds, then fill it with coarse organic material, compost and growing mix.

Moving containers

Decide where a container will live before you fill it. Move large ones while they are empty, or on a trolley.

This guide is based on Chapter 3 of Growing Vegetables in Small Spaces.