(1916) Planting Irises by Jenkins

Gardeners’ Chronicle p.264, December 2, 1916

THE PLANTING OF FLAG IRISES. [The start of a Debate, follow links at end]

In endorsing my views as to the best time for planting the herbaceous Paeonies, namely, before the emission of the new root system, J. F. (p. 211) says lie " would extend the practice to Christmas Roses and Flag Irises." I quite agree; but he goes on to say that the Flag Irises " may be divided and transplanted any time after the flowers are over, but not later than September," a remark which I cannot endorse. Flag Irises only agree with Paeonies and Christmas Roses in that all are periodical in their rooting : producing, virtually, but two sets — primary and secondary — of roots each year. In the two last-named the primary or " basal roots " issue at about the same time — September — hence the importance I attach to this time for their planting. In the Flag Irises these primary roots are emitted at a wholly different time — early spring — hence March and April are the best planting months.

The aim of intelligent planting should be to arrive at a good representative flowering with the least possible delay. This in the case of the "Bearded" or "Flag" Irises is only achieved by March planting, preference being given to the earlier month in order to be "in advance " of new root formation. Where for any reason it cannot be done at that time, I place August- September as a fairly good second. At that time leaf and rhizome are fully developed ; the germ of the ensuing year's flowering is fully laid, and, albeit that there will be found on examination a loss of the earlier-formed root-fibres, and a, modified development of the plant, the flowers, though somewhat smaller, will issue in duet season.

Dividing and transplanting these Irises " any time after the flowers are over," as recommended by J. F., is wrong in principle and bad in practice, yet growers of repute, amateur, commercial, and some of those in public gardens continue to divide and transplant at the wrong time. Even so great a student of the genus Iris as Mr. Dykes falls into the common error, and advises gardeners, in Irises (Present-day Gardening Series, Chapter XIV.), about " shifting Irises when they have only just finished flowering, or even when actually in bloom." It is advice of this kind which sends the ordinary gardener and amateur astray. Continuing, Mr. Dykes remarks: "The reason is obvious to anyone who has ever taken the trouble to examine the root system of the Iris." It is; though Mr. Dykes himself is apparently one of those who has failed to grasp all the potentialities of this root system.

Further, Mr. Dykes says, to insure success, then, in transplanting Irises, they should be shifted in time for the main roots to go down uninjured into the soil." I entirely agree. It is a complete endorsement of a practical experience of thirty years with these plants. Unfortunately, Mr. Dykes fixes on the wrong time.

The "Flag" or "Bearded" Iris commences to produce its main roots in March or thereabouts, contemporaneously with the new growth, and divided and transplanted at that time they are prodigal of good results. Planted at any other time, it is impossible for " the main roots to go down uninjured into the soil." The great advantage of March planting is that a maximum development of primary root, leaf and rhizome is promoted unchecked in proper order ; a fact which also accounts for plants so treated flowering cent. per cent. the following year. Planted at flower-time, when the main roots have made considerable progress, mutilation and loss ensue, and the plant, dependent upon the thereby enfeebled secondary, or lateral root- fibres, has to put in another season's growth ere it is capable of a good representative flowering. Truly. as Mr. Dykes observes in the chapter referred to, " Rhizomatous Irises have suffered much from the very fact that their hold on life is tenacious," since the ignorant and unobserving take liberties' "with these long-enduring plants.

When in 1913 a trial of Iris was contemplated at Wisley — the plants being asked for in July —I made representation in the proper quarter that the planting time fixed was wrong, and that March was by far the best month for the work. Eventually, acting on suggestions I had made, a private trial, unknown to myself, was conducted!, six plants each of three varieties being employed. The following table gives the results : —

Dismissing the October flowering throughout as erratic, all else will be seen to greatly favour March planting. The report on the experiment will be found in the Journal of the R.H.S., Vol. XLL, Part 2, December, 1915. E. H. Jenkins. ( Dykes' response; continued debate Jenkins, December 12, 1916)

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

-- BobPries - 2014-06-24