Three years ago I began a very unscientific study of flowers per square foot in spring. My targeted plants were peonies versus iris, particularly bearded iris. Which of the two gave me more flowers per square foot? And when I say unscientific, this was from observation only.
Even with my lackadaisical approach, it became evident that peonies gave more color, square foot for square foot, plant for plant. The answer only lead me to analyze why. Could I do something to increase the advantage of my iris? The answer is a simple one, and it’s all about maintenance.
They cycle for many perennials is a period of root growth, sometimes followed by a spurt of growth. With bearded iris, this spurt comes in mid-August. Fresh roots go down, rhizomes are formed up top. If the foliage and crown is overtaken by other plants during this critical growth period, the floral display will be compromised, not a maybe or possibly but a certainty.
Peonies also put out new roots in a cycle. Their root growth is much later, more like early winter. This root growth won’t become a growth spurt until spring, when most plants around them are slow to emerge or still dormant. The timing of new growth occurs when little else is coveting the space and light reaches their new leaves. A peony clump will also grow as a dense plant with light reaching the uppermost leaves, feeding the plant more successfully than iris.
Based on my observations, the critical time to remove overgrowth from iris in now. Lax stems of aster, baptisia, amsonia, phlox, and other perennials will threaten the flowering capabilities of your bearded iris. The more light that reaches the rhizome, the better the floral display.
In my second year of following this maintenance plan, I saw better results. I’m sure that spring of next year will give me more flowers per plant on my iris than the previous year. August is the month to begin preparations for spring.