Buy petunia seeds online from Kings. These are another of the garden's versatile plants that can be grown under all conditions and in different situations. A must-have for hanging baskets! We have all types including multifloras, granifloras and millifloras in a range of colours. Sow petunia seeds in pots or trays in the greenhouse at 18°C from February to March. Seedlings will be ready for pricking out in about 7 weeks, unless, of course, you are using plug trays, in which they can be left to grow on. Do remember to give the petunias some feed when watering. Plant out as soon as the chances of frost have gone. They will flower virtually straight away and last right through from June onwards.