(1916) The Planting Of Flag Irises by Dykes

The GardenersÂ’ Chronicle p.282, December 9, 1916


Mr. Jenkins' article on this subject ( see p. 264) has appeared at a time when it was already in my mind to write a note suggesting certain modifications in the rule that I have hitherto observed, namely, to endeavour to transplant my Irises as soon as possible after the flowering season. I was going, however, to advocate a later, and not an earlier, period of the year, and Mr. Jenkins' article has not converted me to his view.

Statistics are often deceptive, and the figures which, on the surface, seem to support Mr. Jenkins' contention, suggest on closer examination that they may equally well be used as an argument against his view. In the first place, the first flowering season after planting, namely, May, 1913, is altogether omitted, presumably because plants shifted in March could hardly be expected to flower in the following May. Secondly, Argus transplanted in March produced 16 spikes in 1914 and 58 in 1915, increasing to rather less than four times the number, while those transplanted in June increased no less than eight times in the same period, namely, from 4 to 32. For Gracchus the figures also show that from 1914 to 1915 the June-planted specimens increased faster than those trans-planted in March. The figures quoted for Queen of May do not, it is true, support my view, but I am confident that most Iris growers will agree with me that if six plants of this variety were planted in 1913 and gave only three flower-spikes in 1914 and only four in 1915, there must have been something seriously wrong either with the plants selected, with the planter, with the planting, or with the position chosen. Not having any weather statistics at hand, I am unable to suggest any definite reason why the plants moved in June, 1913, flowered so poorly in 1914, but I should not be surprised to find that a period unusually dry, or in some other way exceptional, was the cause of their failure.

If it has been Mr. Jenkins' invariable practice for thirty years never to transplant Irises except in early spring, he has doubtless forgotten that new main roots are pushing out from the rhizomes certainly as late as August, and often even in September. We must remember that an Iris rhizome is not a stationary bulb, but a creeping stem which grows by travelling horizontally, and travels only by putting out fresh roots all through the growing season. Even among bulbs and corms there are two distinct classes, those which, like the Tulip and the Crocus, send out all their annual output of roots at one period of the year, and those which, like most Narcissi and the Gladiolus, are practically always sending out fresh roots unless they are lifted and dried off.

Mr. Jenkins, it seems, wishes us to believe that the Iris behaves like the Tulip or the Crocus, whereas the fact is that it resembles rather the Narcissus or the Gladiolus in producing a few roots at intervals over a long period. This period begins in spring, and continues throughout the summer into the autumn, and doubtless if we always had genial growing weather in March and April, and if we were content to lose the first flowering season entirely, Irises transplanted in March would be better prepared for the flowering season some fourteen months later than those moved later in the season. Unfortunately in March and April we often get long spells of east winds, beneath the influence of which freshly moved plants suffer visibly, and. moreover, we are not always willing to sacrifice the first flowering season.

There is a further point. No Rhizomatous Iris continues to grow in the same straight line beyond the flowering point. The flower-stem is the end of the axis, and growth is only continued by lateral branches. My impression is (but I admit that I should still like to make some observations on this point next spring) that when growth ceases in autumn a rhizome which is going to flower in the following spring has reached the point at which it will flower, and has formed all the roots that it ever will form on that axis, and that the new root-activity in spring is devoted to the extension of the lateral growths which are to carry on the life of the plant after the death of the flower-stem.

Obviously then, if we move our plants in March we sacrifice the first flowering season. I think Mr. Jenkins must admit this. The question then arises, if we prefer not to make this sacrifice, shall we transplant immediately the flowers fade, or shall we wait till July or August? This year I had occasion in August to lift a number of Irises, and I found that each rhizome then possessed a number of stout roots, which were still unbranched, and that it also showed obviously that yet other roots were still to emerge. At the flowering season the new roots are immature and exceedingly brittle, so that there is considerable danger of injury unless the plants have only to be moved a short distance, and need not remain out of the ground for any length of time. Under these conditions it has certainly been my experience that Irises moved in June suffer in no way, especially if in dry weather some water be poured into the bottom of the hole before the roots are put in.

If the plants have a journey to face, I am inclined to think that there is less danger of damage when the majority of the primary roots are mature and as yet unbranched early in August, and that this is, then, the best period at which to transplant them, always provided that they get a liberal allowance of water at the roots if the soil is at all dry. Both in June and in August there is always a danger that even with great care the tender points of roots which have hardly emerged from the rhizome will be damaged ; but whereas in June those roots which have rushed out are only partially developed, and therefore easily broken or withered by exposure, in August a fair number are mature, and therefore able to withstand handling and packing with less risk of injury. Moreover, the soil is warm, and there is still time for the secondary lateral fibres to develop, and for a few more main roots to push into the ground before growth ceases for the year. W. B. Dykes, Charterhouse, Godalming.

( Jenkins' response, December 16, 1916)

For more information on historic Irises visit the Historic Iris Preservation Society at

-- BobPries - 2014-06-24
Topic revision: r1 - 24 Jun 2014, BobPries
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