Related to kale, broccoli, and Brussels sprouts, watercress is a   peppery-tasting, leafy herb naturally found growing in gently running water   forming dense mats of nutritious, edible foliage. While it prefers a moist  spot in full sun, it can be grown indoors in a water-filled container to extend  the season.
                                    
                                        Growing instructions:
                                         Sow seeds into very moist seed compost in pots   or trays at 61-64°F (16-18°C). Prefers a shady position to germinate which   takes approx. 1-2 weeks. Plant out into reliably moist ground, or a regularly   watered windowbox, and pick regularly to ensure juvenility and to prevent   premature flowering.
                                     
                                        
                                            Eventual height:
                                            0.15m
                                            Eventual spread:
                                            0.15m
                                         
                                        
                                        
                                            Rate of growth:
                                            Fast-growing
                                         
                                        
                                        
                                    
                                        
                                            - 
                                                
This perennial dies back to below ground level each year in autumn, then fresh new growth appears again in spring.