Maintenance: Old growth and flowers should be cut back to the ground to allow new growth annually. Removal of stems, which die out every 2-3 years. Removal of spreading rhizomes to keep the clump to the desired size. Removal of suckers. Apply a slow release 14.14.14 NPK in spring and autumn. Wash down occasionally to remove wind blown sand and dust. Sap may cause contact dermatitis to those with sensitive skin.