This semi dwarf mix is stunning in the middle of borders or containers and beds. These come in a mix of colours such as pink, orange, yellow and red. These are compact and do not need staking making them perfect for cottage garden borders, they are also ideal for cut flowers. How to Grow Plant Dahlia tubers outdoors in April after all risk of frost has passed. Choose a sunny position in moist well drained soil. Prepare the soil by digging in plenty of well rotted manure or compost. Plant tubers at a depth of 15cm (6") and water well. Alternatively, start tubers into growth in pots of compost in a frost free greenhouse. Transplant them into their final positions outdoors in June. Feed and water dahlias regularly throughout the growing season. While dahlia plants are still young, pinch out the growing tip of each stem to encourage bushier growth and masses of flowers. Deadhead faded dahlia flowers to encourage more blooms to be produced. Bedding dahlia are generally grown as annuals, how