One of the loveliest and most colorful beds in bloom in early summer here at the Garden is the Japanese Iris “pond”, a large island bed situated just below the parking lot. Now just beginning to bud, the “queen “ of the iris world will soon provide us with the most spectacular display of huge blossoms as much as 6-8 inches across. The falls (lower petals) are held horizontally, are often doubled (in sixes rather than threes), and frequently ruffled, veined, stippled or sanded in appearance as the color flows from white centers surrounding a bright yellow signal to outer edges richly saturated in tones of lavender, violet, purple and blue. These magnificent flowers are most effectively displayed en masse but will feature as striking accents in a mixed border providing they are given the necessary growing conditions.
Ideally, the planting bed should be in full sun and be moderately acidic, nutritionally rich and well amended with manure or compost. Soil amendments and fertilizers which tend to raise the PH, such as mushroom compost, bonemeal or lime should be avoided completely and it is essential to keep the soil constantly moist. Very wet soils such as pondside borders are ideal but the crowns should never be submerged. Once established, an annual application of an acid based, high nitrogen fertilizer in spring will keep the plants happy for about 4 years, at which point they will need to be dug and divided or they will lose vigor and perform poorly. Mulching is recommended, and we have found that interplanting with unfussy, vigorous tall annuals such as bachelor's butttons or cosmos is an ideal solution to minimizing the uninteresting appearance of the leaves after blooms are finished. Once the leaves have started to yellow in the fall, the plants should be cut right down and the debris removed. This iris is hardy down to zone 4 and will be completely dormant throughout the winter months.
Although the cultural requirements are more demanding for Iris ensata, the Japanese iris, than for some of the other beardless varieties, the beauty of the flower in bloom makes the work very worthwhile. If you are an iris lover, this is a must for your garden. To see our bed in bloom, you will need to visit in mid to late June; be sure to bring your camera.