. ▁ ▁They ▁also ▁can ▁be ▁grown ▁in ▁containers ▁( even ▁in ▁the ▁water ▁or ▁bog ▁garden ) ▁but ▁they ▁must ▁be ▁re - p otted ▁and ▁divided ▁every ▁year . ▁ ▁If ▁using ▁a ▁fert il izer , ▁spr ink le ▁around ▁the ▁plant ▁in ▁late ▁January ▁or ▁February , ▁before ▁the ▁plant ▁is ▁in ▁flower . ▁ ▁New ▁plant ings ▁need ▁to ▁be ▁mul ched ▁to ▁prevent ▁sun - scal ding . ▁Plant ings ▁in ▁the ▁water ▁do ▁not ▁need ▁mul ch ing ▁and ▁tend ▁to ▁grow ▁quick er ▁than ▁others . ▁ ▁Pro pag ation ▁Pro pag ation ▁is ▁best ▁carried ▁out ▁by ▁division ▁of ▁the ▁rh iz om es . ▁Which ▁is ▁best ▁carried ▁out ▁in ▁late ▁summer , ▁when ▁the ▁plants ▁are ▁d orm ant . ▁The ▁ground ▁must ▁be ▁prepared ▁pre - plant ing , ▁with ▁the ▁addition ▁of ▁a ▁gener ous ▁amount ▁of ▁organ ic ▁matter ▁and ▁the ▁so ils ▁d ug ▁to ▁about ▁ 6 ▁inches ▁deep ▁( to ▁allow ▁for ▁new ▁root ▁growth ). ▁Pl ants ▁require ▁div iding ▁every ▁ 3 – 4 ▁years ▁to ▁promote ▁good ▁flow ering . ▁They ▁can ▁combine ▁with ▁other ▁plants ▁but ▁tend ▁to ▁' move ' ▁to ▁suitable ▁positions . ▁ ▁The ▁ir is ▁seed ▁is ▁not ▁hard ▁to ▁raise ▁but ▁a ▁very ▁slow ▁process . ▁It ▁can ▁take ▁many ▁months ▁to ▁germ inate ▁( between ▁ 3 – 1 2 ▁months ) ▁with ▁a ▁ 5 0 % ▁germ ination ▁average . ▁They ▁then ▁can ▁take