I planted a giant hyssop and a regular anise hyssop June this year, they both grew and established very quickly. However, they are tall and a bit weak in that the top with the flowers are falling over on their neighbours. How do I maintain it this fall and next spring so it does not fall over.
Lovely choice of plants! To keep them from getting too tall and droopy, the best approach is to prune the anise hyssop (Agastache foeniculum) or purple giant hyssop (Agastache scrophulariaefolia). Cut back up to 1/3 of the plant (just above bud nodes) in early spring to stimulate new growth. Until early summer, encourage bushy growth by pinching back new growth using your fingers or pruning shears – this helps shape and strengthen the plant. Deadhead the flowers (this may help somewhat with the drooping and also prevents prolific self-seeding – although birds enjoy the seeds as part of their diet!). However, if you prune the plant later than mid-summer, this could stimulate new growth in the autumn that may not survive the coming winter. Every 3-5 years, divide the plant as the centres tend to die out.