Growing Parris Island cos is no different than growing any lettuce plant. Seeds can be sown directly in the garden and will mature in about 65-70 days. They should be planted in rows set about 36 inches (91 cm.) apart and thinned so that plants are no closer than 12 inches (30 cm.) apart. Lettuce plants require about an inch (2.5 cm.) of water per week for optimal growth. If growing Parris Island cos lettuce during the hot summer months, they will require extra water to prevent bolting. Keeping the soil cool and moist with layers of mulch or straw will also help it grow through difficult weather. Keep in mind that, like most lettuce types, slugs and snails can sometimes be a problem.