This perennial dies back to below ground level each year in autumn then fresh new growth appears again in spring. Position full sun Soil well-drained fertile soil Rate of growth average Flowering period July to October Hardiness hardy borderline Hyssops are great for adding vertical accents to a border with whorls of long-lasting tiny flowers arranged like a bottlebrush and pointed aromatic fresh green leaves that are attractive to butterflies and bees. They are short-lived though and may need replacing every few years especially after a cold or wet winter.