WEEDS AND THEIR IDENTIFICATION.

New Zealand Journal of Agriculture, Volume XXXVI, Issue 3, 20 March 1928, Page 201

WEEDS AND THEIR IDENTIFICATION.

Esmond Atkinson,

( Continued.)

Biological Laboratory, Wellington.

SPEAR-GRASS (STI PA SET ACE A). ' . The grass illustrated in this article has been known in New Zealand for fifty years or more. It was first discovered in Otago, and was then thought to be an undescribed native species, being given the name of Stipa Petriei* Only after some time-when it had begun to spread considerably and showed unmistakable signs of being an introduced plant'—was it found to be the same as the Australian Stipa-setac'ea. Cheeseman (“ Manual of the New Zealand Flora/’ 1906, .p. 858) describes spear - grass under this name, but, while including it among the indigenous grasses, remarks : “A common Australian plant, stretching from Queensland to Tasmania. It is probably naturalized only in New Zealand.” In the Appendix he says : “I have received numerous specimens of this plant from various localities on the east coast of the South Island from Marlborough to Otago. It is evidently spreading rapidly, and no doubt can be entertained of its exotic origin.” In the second edition, of 1925, however, it is still included among the native species. Little has been heard of spear-grass as a weed in New Zealand (though in Australia it has proved troublesome from time to time) until within the last few years, when it • has spread rapidly on Banks Peninsula and in the Marlborough Sounds. Lately there have been a good many inquiries about it at this Laboratory, on account of its danger in sheep-country.

Spear-grass is a striking plant when in flower, owing to the graceful, open head, with its unusually long awns. (The awn is the bristle-like attachment to the scale which forms part of the covering of the so-called “ seed ”in grasses.) Fig. aof the illustration shows the general appearance of a head, but larger ones than this, with many 'more flowers, are often seen. The whole grass is slender and wirylooking (Fig. d), even the leaves being so, owing to their inturned edges. Fig. & shows (magnified) the junction of leaf and leaf-sheath with its tufts of hairs. At Fig. c (also magnified) is shown the “ seed,” sharply pointed at the lower part, and at the opposite end the base of the awn, which is spirally twisted. It is these sharp-pointed “ seeds,” with their long twisted awns, that make spear-grass so troublesome a weed under certain conditions. The following quotation from Hilgendorf’s “ Weeds of New Zealand ” (p. 27) gives a very clear idea of. the actual damage done : “ Each seed has a very sharp spike, and the twisted awn helps to drive this spike into sheep's wool. The seed sometimes penetrates the pelt, and embeds itself in the subcutaneous muscle, entirely spoiling the appearance of the carcase. An area of 3 square inches of the surface muscle of a sheep killed at Picton works was found to contain thirty-three seeds of spear-grass. The tails had broken off as the seed had passed through the skin, and only the heads were embedded in the muscle. . The pain, and consequent loss of condition, to the , sheep must have been

very serious. It appears that only occasionally does the seed ripen hard enough to act in this manner, because in some cases where speargrass is found the sheep are not affected.”

This article is written primarily with the idea of showing what spear-grass is like to look at, so that where it has only recently made its appearance there may be no delay in recognizing it. It is too early as yet to formulate any definite rule for combating the weed, but the owners of country where spear-grass is spreading are likely to have noticed many points about its behaviour under varying conditions. The possession of such facts from a wide range of country would, when they were correlated, certainly be of great value in dealing with a weed like spear-grass, and any information sent in to the Department of Agriculture would be appreciated.

* Buchanan: “New Zealand Grasses,” Plate 17, ii.