This weekend I saw that one clump of Japanese iris (Iris ensata, below) close beside the waterfall of the large koi pond was dangerously crowded by overhanging branches of an exuberant Oakleaf hydrangea (Hydrangea quercifolia). On the other side of the falls a rambunctious Winter jasmine (Jasminum nudiflorum) has invaded another clump, and both shrubs required immediate attention to be certain that the irises were not overwhelmed. The pruning was accomplished without much effort, but in the future I must be vigilant to monitor the shrubs’ growth so the irises aren’t lost.

Just outside the pond, a clump of iris with large, dark purple flowers has sprouted from seed (below) between the columnar, red leafed ‘Helmond Pillar’ barberry, a low, mounding cypress, and yellow leafed seedlings of ‘Golden Jubilee’ agastache. As often happens, this accidental grouping is a superior combination to anything I’ve planned, so of course the irises will be kept, and encouraged. A year ago this iris was barely there, and I could have easily plucked it out as a weed if I was inclined to keeping the garden more tidy. Now, the challenge will be to keep the iris growing in ground that is drier than it would prefer.

In the shallow water of the pond, named cultivars (though I’ve forgotten most of the names) grow vigorously, flourishing with their roots constantly wet. Outside the pond, Japanese irises require a constantly damp soil to thrive, but wedged between small boulders and planted in only gravel in the pond the irises spread to fill as far as the boulders will allow. I’ve read that Japanese irises require only constant moisture, and dividing once every few years, but the roots of the pond’s irises are spread through gravel and under boulders so that lifting them would be troublesome, so they are likely never to be split.

The green and white variegated iris (Iris ensata ‘Variegata’, above) is the shortest growing of the cultivars, and in some years it has seemed less vigorous so that I considered pulling the clump out to divide it despite the hardship. But, as often happens, if a garden project is delayed long enough the problem is resolved by doing nothing at all, and today the variegated iris appears to be in perfect health. The dark purple flowers are splashed with a slight streak of yellow, and in scale with the shorter foliage, the blooms are smaller than other varieties.

‘Lion King’ (above) is the latest flowering of the irises in the pond, and it seems to be the least vigorous with the clump barely increasing over several years. The flowers are quite marvelous, but I wonder if the sturdiness of other Japanese irises was left out in the breeding process. But, it survives, and I look forward to the blooms that arrive just as other varieties are fading the third week of June.

From start to last bloom Japanese irises flower for about a month surrounding my koi pond in mostly full sun. In prior years I planted them in damp soil with what I thought was just enough sun, with only brief success. For two years they bloomed fine, but it was clear they weren’t happy and after another year they disappeared completely. At the edges of the pond they’re planted and enjoyed with no care except to cut off the overwintered foliage in early spring before they begin to grow.