A watering and fertilizing device comprises at least one fertilizing column and a water supply system. The fertilizing columns are vertically inserted in soil, surrounding roots of a plant to be watered. Water from the water supply system enters the fertilizing columns, taking along fertilizer contained therein and further dripping into surrounding soil at a constant rate, so that the plant is effectively supplied with water and nutrients without waste of water. The water supply system optionally provides besides water water-soluble fertilizer, which flows into soil along with water.