The Air They Breathe

Air circulation, both above ground and below, is another thing herbaceous perennials need. Pore space in soils provides room for root and the exchange of gases essential for growth. Soils that are anaerobic will not support herbaceous perennials. Breezes and wind draw moisture away from plants susceptible to foliar diseases, spread seeds and support the movement of pollinating insects. Too much air movement can be detrimental, causing desiccation of leaves with thin cuticles or pale pigments, browning or aborting of flower buds, and general 'wind burn' to susceptible herbaceous plants. What can we control or manipulate regarding air circulation for herbaceous perennials? Improving the soil structure, avoiding working soils when they are wet, and minimizing additional compaction help maintain pore space for underground air circulation. Modifying air movement by spacing plants far enough apart to allow air movement can help reduce disease. Dead or stagnant air combined with high humidity can be compared to the 'wet blanket' days of a hot, humid summer, and perennial plants, particularly those more suited to a dry environment, will suffer. Providing protection from the most severe winds by placing herbaceous plants behind fences or woody plants will help avoid dessication and loss of flowers. Choosing plants with characteristics that make them capable of withstanding severe winds where the effect of the wind cannot be mitigated is the only sure way to achieve an acceptable landscape. But we can't make the wind stop blowing, or introduce it when the air is too still.