Pelargoniums are fantastic plants for providing colour and in some cases scent from June to the first frosts. Most people are familiar with the upright Zonal types (erroneously called Geraniums) but there are so many more from trailing, double flowered, bi-coloured, scented-leaved to climbing or scrambling varieties. Many cultivated varieties have been bred but 90% of wild species originate from South Africa so with this in mind they need protection from frost and the worst of the wet weather. They make excellent container plants for outdoors in summer. You just need a conservatory, greenhouse or bright porch to keep them protected over winter.
Grow in a good loam based compost with plenty of added grit. They like lots of sun but may scorch in a very hot conservatory. Most do best if put out for the summer. Feed bi-weekly with tomato food when in flower. Don't over water Pelargoniums they hate it! You may find you only need to water them once a week even in summer but check the compost regularly and water when they feel they are dry.
By the end of September (UK) you will need to think about bringing them under cover before they get frost. Trim them back by about third and remove half of the leaves to maximise air circulation through the plant. Pelargoniums hate poor air circulation and can fall victim to grey mould (botrytis) if kept in close, damp conditions. Never cover them with plastic and don't pack them together try to give them space.
Pot up in spring or re-pot with fresh compost if you want to retain the same pot size. Add some slow release fertiliser to the surface of the compost. This will gently feed them as they slowly grow away. Keep above 2°C.
