If you don’t need a professional gardener or landscapers, you can make a planter in any style by using ferroconcrete— and you do not need a mould. Although the technique is quite simple, it takes some practice. But fortunately the materials are very cheap, so you can afford to make several planters. The basis of the planter is a wire form, which gives it both strength and shape. Make it from lengths of galvanized baling wire and chicken wire mesh.
The more wire you use, the stronger the resulting planter, but the harder it will be to pack with mortar. You can make the form in any shape, but the simple flower pot shape shown is the easiest. Make up a 2:1 mortar mix and add some plasticizer to make it easy to work.
Plaster the mould with this, wearing rubber gloves to protect your hands. Work it thoroughly between the wires from both sides. You should aim to build up a 20mm thickness with the form embedded in the centre. It does not matter at this stage if the finish is rough, because you can trim off the excess when the mortar goes ‘off using a trowel, a length of batten or scrapers. The same tools can also be used to add details such as rings or a plinth. Leave a drain hole in the base, then set the assembly aside to allow the mortar to cure. When it is thoroughly dry, fill with earth over gravel. If you want a more decorative planter, add some colourant to the mortar mix or stain it when dry.