In theory, as long as a thing is capable of holding a reasonable amount of compost, you can grow something in it, and you do not have to spend a lot of money on something specifically designed for the purpose. Here are a few ideas for improvised containers:
Plastic and metal ice cream and other large catering containers
These are not suitable for using outside in winter because frost can penetrate easily, freeze the compost, and kill the plant, but they can look quite decorative in summer, especially if the sides are concealed with trailing plants and they are, of course, free of charge. They are only temporary as the plastic eventually becomes brittle and breaks, and the metal ones usually rust. They need drainage holes in the bottom, otherwise they become waterlogged. They may look a bit austere but can be painted in pastel or gay colours – quite effective in the right place, and it prolongs the life a little.
Plastic and galvanized buckets, bowls, baths, etc.
The same remarks apply as for the previous items. Large, heavy wooden boxes. These can blend in quite nicely, especially if treated with a coloured spirit wood preservative (not creosote). The timber of which the box is made should be fairly thick. The box should be slightly raised from the ground it stands on with bricks or similar to prevent the bottom rotting quickly.
Stone and earthenware sinks and troughs, old baking bowls and similar kitchen equipment
These are certainly not cheap to buy — if you can find any – but look very attractive. Sinks can contain dwarf shrubs or bedding plants, or can be planted as ‘sink gardens’. Sometimes you can pick up old white glazed sinks and other obsolete sanitary equipment at a nominal cost from plumbers and builders. These can be coated with a PVA adhesive and then covered with a mixture of equal parts cement, sand and peat to make them look like stone, but it is fiddly. A quicker method is to paint them with car undersealing compound and then shot-blast them with coarse sand and pea gravel while the bitumen is still wet.
Earthenware containers are not really suitable for outdoors in winter as the frost can sometimes crack them. They should have drainage holes in the bottom or they will become waterlogged.
Old chimney pots
Again, these are not cheap, but can sometimes be found in antique shops. They are an awkward shape to plant successfully, but trailing plants like ivies look nice.
Laid un-mortared, these make good plant holders up to 18 in. (450 mm) high and if they are not permanently bonded, they have the advantage of being movable if you want to change their position.
If troughs are constructed of brick, mortared or otherwise, and placed against a wall, the wall should be thoroughly damp-proofed with polythene, felt or similar before filling the container with compost.
This comprises split logs, wired together along the flat side and is usually used for edging beds and paths, but can be made into a circle to form a well insulated and attractive planter.