Several clumps of Japanese iris (Iris ensata, above) surrounding the koi pond have been invaded by yellow flag (Iris pseudacorus, below). These are pried from the tangle of roots with great difficulty, and with only limited success. Yellow flag works splendidly to populate the gravel bog filtration area of the pond, but if left alone the vigorous iris will overwhelm the slightly less robust Japanese iris.
Several seedlings of Japanese iris (below) have sprouted in shallow water between stones at the pond’s edge, but also an exuberant seedling grows several paces outside the pond in dry ground. I suspect that irises are easily crossed, and that many hybrids are discarded by breeders as nothing very special. Probably, several that grow in this garden would not pass muster, but these are plenty good enough by this gardener’s low standards.
Each clump of iris flowers for just over a week, but if several cultivars are chosen it is likely that flowering will extend for several weeks or a month from start to finish. I would fib to boast that varieties were chosen with intent to extend blooming, and I suspect that if three were chosen randomly the gardener would enjoy three weeks of flowers. If five (or fifty) are planted there will be flowers for a month, and no longer.
I have tried, and failed, planting Japanese irises in drier ground with the exception of the tall, purple flowered seedling. This has grown into a thick clump, and I rejoice that I did not pluck it out as just another weed. It’s sword-like foliage stands above a low mounding cypress, a better design accent than I’m able to imagine.
In shallow water, planted in one inch gravel, there is no secret to growing Japanese iris. Larger stones constrain the irises from spreading further, and after a year or two the clump will fill a square foot area. In damp, but less soggy soil growth is a bit slower, but irises planted fifteen inches apart will fill the space in three years. At least, this has been planned for a damp area of the rear garden that has become progressively more waterlogged in recent years.
While only one cultivar has been planted, I expect others to be added to extend flowers from mid May into June.