Sow outdoors May. Sweet corn can be sown outdoors for ease. Choose a sunny, sheltered location for best results and wait until the soil has warmed up, ideally to around 10°C or more. If the soil is very heavy, cold or waterlogged an indoor sowing is preferable. Sow 5cm deep directly where plants are to grow. For surest results, sow two seeds together, with 40cm between each pair and in a block formation to help the wind pollinate all of the cobs. Gently firm the soil and keep moist. When large enough to handle remove the weaker seedling of each pair, leaving the strongest to grow on. It is good practice to water well after thinning out, to wash any dislodged soil back around the roots of the remaining plants. Remove any weeds as they appear.