Art. XLVIII.—On the Growth of Phormium tenax.
[Read before the Auckland Institute, 24th June, 1872.]
The growth of the Phormium plant, the period of its decay, the increase of its off-shoots, and more particularly the rate at which the leaves are produced, and the time required to bring them to maturity, are questions of great importance to those interested in the manufacture of the fibre.
The attention of the Flax Commissioners, when making their inquiries last year, was directed to these points; the mode of growth, and its increase under cultivation, were ascertained with some approach to accuracy, and are stated in the pages of their report; 357 but as that report has not yet been generally circulated (though I am glad to say that it has just been reprinted with the latest information that can be obtained), and as I have procured specimens to illustrate what they have noted, I will repeat the substance of their observations.
The plant when full grown consists ordinarily of a rhizome or prostrate stem, from the under side of which numerous fibrous rootlets strike into the ground, and from the extreme end a number of leaves proceed in succession, decaying and falling off after arriving at maturity. At a certain period a flower stem shoots up from the apex, after which the whole of the leaves and their rhizome having completed their functions die away; but every year various fresh side shoots have started from the main rhizome, forming separate fans with roots and leaves, receiving at first nourishment from the parent stem, and gradually becoming independent plants, producing further shoots, and dying away after perfecting flower and seed. In dry, hard ground the rhizome is but imperfectly developed, and amongst sand-hills it becomes a vertical stem several feet in length, seeking its nourishment at that depth where abundant moisture is to be found.
[Footnote] * App. to Journ. H. of R., 1871, G. No. 4.
Some few attempts have been made at cultivation, but the slowness of growth of transplanted sets, and the great expense, have not given capitalists much encouragement to form plantations on a large scale for the supply of the raw material. It was found that the average rate of multiplication of sets did not exceed six in three years, and even at the end of that period the plants were not sufficiently established to supply a succession of well-grown leaves for manufacture, whilst the first cost of planting was very expensive, and in the case of a field of twenty-five acres near Patea was as much as £18 per acre, exclusive of fencing and clearing the ground.
Seeds sown in the Botanic Gardens at Wellington in the month of November, 1870, were above ground in twenty days, but at the end of ten months the most vigorous plants were not more than a foot in length, and others sown in a nursery garden near Wanganui, in soil of the richest possible description, from two to four feet deep, and irrigated in hot weather, after a growth of sixteen months were only single fans of four or five leaves, averaging two feet long by three-quarters of an inch in width; and it was evident that they would require several years more to grow into a bush which would bear cutting for fibre; although seeds of only the best varieties of tihore were sown, the young seedlings did not show any marked resemblance to the parent plants, but were of all varieties of colour.
In a large flax field, where all sorts of varieties may be found, the plants growing in the same description of soil are much of one size; the luxuriance of growth depends not on the variety, but on the nature of the soil in which they have established themselves. To illustrate this I have here several fans of the rataroa, one of the best varieties of tihore, grown at St. John's College from sets that were procured by Bishop Selwyn some twenty-five years ago from the East Cape. You will observe how greatly they vary in size and luxuriance. The large fan, with leaves nine or ten feet long, is from a plant which grew in the lowest, wettest, and richest part of a drained gully. The other specimen grew on a poor clay hillock; and there is every gradation between the two, according as the soil was wet and good, or poor and dry; yet they are all the same variety, and I believe the fibre is equally good for manufacturing purposes from each—it is, at least, as strong, and can be stripped out in Maori fashion with the same facility.
The Phormium attains its greatest size by the banks of streams, where there is plenty of running water to nourish the roots. In very wet stagnant swamps it is never so good, but improves immediately the swamps are drained.
The information obtained by the Commissioners with respect to the growth of the leaves was not so exact, as sufficient time to make the necessary observations had not been afforded them. They, however, ascertained from a variety of testimony that if a flax plant were cut quite down, there would be
a fresh growth of from four to six leaves within a twelvemonth; and they found that there was no constant difference of strength and quantity of the fibre procured from the various leaves of the same plant; but they were not able to determine what was the normal rate of growth of leaves in uncut plants, nor when each leaf had arrived at maturity. The opinions of manufacturers varied very considerably on these points—some supposing that the leaf required several years to reach its full growth, at all events that it did not commence to decay until it had remained for a long time in a state fit for manufacture.
For the purpose of settling this question, in the month of May, 1871, thirteen months ago, I marked the young centre leaves just shooting up in a number of the plants at St. John's College, and found that by September, during the four winter months of the year, in every instance at least one fresh leaf had made its appearance and taken the others' place, and in November, two months afterwards, these had again been replaced by fresh leaves. I found a more rapid growth in the summer months, so that in the course of the year generally six, or at least five, fresh leaves had been produced in every instance. I have two of the fans that I marked in this manner. One leaf marked “May, 1871,” was the centre leaf thirteen months ago, it is now the seventh, and has already begun to decay; and the other leaves were marked at intervals, giving an average of two months for the growth of each leaf.
In two other fans I cut all the leaves at the same height from the ground on the 5th April last, and now observe that only the three centre ones in each plant have made any further growth, showing that the others were fully developed and had reached their full size, and that this maturity has been attained within six months of the first appearance of each leaf.
As to the age of a plant, or of any portion of it at the time of flowering, I cannot speak positively, and I believe it varies very much. Many of the tihores flower very sparsely, and often fail to perfect seed.
In large Phormium fields in certain years (it is generally supposed every third) there is a profusion of flower stalks (in 1871 in the Wairau plains there was a perfect forest of them), and in other years comparatively few, but we must not conclude that each fan flowers at the end of three years. On one rhizome there are the cicatrices of more than fifty leaves, which at the rate of six per annum would make it eight years old, and on another which flowered the year before there are only twenty-five or twenty-six. It will require several years of close observation to determine this point, but I do not think it is one of any practical importance, as the decay of one fan does not seem to interfere with the growth of the remainder of the bush, which increases as it gets older, the rate depending of course on the soil and locality in which it is found. We have found that with transplanted sets the increase
has been on an average six-fold in three years. I have counted forty-four fans on one that has been seven or eight years planted, and over 200 are often found on well grown bushes in suitable localities. The fan that has flowered, as already stated, invariably dies down the following year, but I have never yet seen an uninjured one which has shown any signs of decay from old age before flowering.
I do not profess to have given you in these remarks very much that is new, but I thought that you would not object to a résumé of what has been ascertained on this subject, and I will finish my paper with the following general conclusions:—
That there is an annual growth of five or six leaves on each fan of allPhormium bushes growing in favourable positions, and that each leaf is mature and fully developed in six months from its first appearance.
That leaves more than thirteen or fourteen months old are generally so decayed as to be unfit for manufacture.
That the practice of mowing off all the leaves of each fan must injure, and will gradually destroy the whole plant.
That the growth of transplanted sets and of seedlings of the Phormium is so tedious, and the expense of planting so great, that the cultivation cannot be carried out with advantage so long as the fibre is prepared only for roping purposes.
That as manufacturers must therefore depend on the existing Phormium fields for the supply of the raw material it is to their interest to use every means in their power to preserve them from injury.