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Tutira

Chapter XXIX. — Fire and Flood Weeds

page 282

Chapter XXIX.
Fire and Flood Weeds.

Previous to the 'eighties the effects of burning out the indigenous vegetation of the run had been almost imperceptible; ground temporarily cleared had immediately lapsed into its former condition. As, however, the flocks and herds of the station increased, the ground consolidated and the bracken growth diminished; above all, as light penetrated to the surface, certain weeds one after another temporarily took possession of the fire-blackened tracts. On the better soils of eastern Tutira appeared such plants as Melilotus arvensis, Medicago lupulina, Medicago denticulata, and Sonchus oleraceous; on lands good and bad, Carduus lanceolatus and Briza minor; on grass lands over which in dry summers fires had run, Bromus mollis; on pumiceous lands, Hypochæris radicata, Silene gallica, Cerastium glomeratum, Trifolium dubium, and, at a later date, Erigeron Canadensis.

Taking these aliens in the order named, field melilot (Melilotus arvensis) has never spread beyond the alluvial lands around Tutira lake. Only after flax-fires great or small did the plant show itself; then on rich grounds left black and bare, it appeared, tall, rank, and luxuriant, for a single season. Toothed medick (Medicago denticulata) and nonsuch (M. lupulina), other fire weeds, throve only on fertile hills and flats; they never even germinated on the pumice lands of the trough of the run, though their seed was prominent in the numerous sacks of tailings scattered broadcast over that area. Neither of these members of the pea-flower family took possession on a great scale: I have never seen Melilotus arvensis spread over more than thirty acres as a dense crop, whilst the others never overran more than a few square yards outside of the garden; they were only to be found prominently on land over which fire had passed.

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Sow-thistle (Sonchus oleraceous) was another most prominent fire plant temporarily possessing hundreds of acres of newly-burnt forest land. I have seen brairds of this weed so thick that whilst the plants were still young and flat on the ground, the surface seemed rather blue-green than green, owing to the young leaves' peculiar hue. On soil deep in leaf-mould and grey with ash, millions upon millions of seedlings germinated. As the cotyledons appeared immediately after the first rain, it was evident that seed had been already strewn on the forest floor; carried by the winds from scattered individual plants surviving on cliffs and natural escarpments, lightly buried in leaf-mould and debris, they had but awaited the call of the sun. The sow-thistle flourished with an equal exuberance after the destruction by fire of flax-swamps.

Prickly thistle (Cnicus lanceolatus) was, in the 'eighties, only to be seen in quantity on the seaward fertile portion of the run. Unlike the weeds already mentioned, each of which blossomed as annuals, thistle growth was dependent on the nature of the soil. On sound marl land after autumn fires the seedlings germinated, became great prickly stars during winter, and blossomed during the succeeding summer. On the other hand, throughout the pumice stretches of central Tutira, it became a biennial, reaching maturity only during the second season.

Another plant, not to be found except after fires had swept the land bare, was the little quake-grass (Briza minor). I have found this handsome species on almost every part of Tutira, but never in any single instance plentiful. It has indeed been discovered by me in such out-of-the-way spots at such early dates that I have sometimes wondered if after all it may not be an indigenous species; repeatedly, moreover, I have got it where before fire the countryside had been a sheet of dense fern, where alien grass had never been sown, where almost no human foot had trod. Guesses, at any rate, can be made at the methods by which most species transport themselves from spot to spot, also as to the agencies animate or inanimate employed, but the propagation and spread of this grass remains a puzzle.

In the early 'eighties occurred two dry seasons during which grass fires were run over the hot western and northern faces of certain portions on eastern Tutira; on the blackened ground then and once again seedlings of brome-grass (Bromus mollis) appeared in so great profusion that other grasses were temporarily submerged in hillsides of waving hay. page 284 “Poor Pretences” was then the name by which this brome-grass was known on the east coast: it may be worth putting on record a suggestion as to how the plant came by such a curious designation. It was a “poor pretence” compared with ryegrass, cock's-foot, and white clover, the mixture sown then almost as a religious duty on Hawke's Bay runs, good and bad alike. So much for the sense; as regards the sound, “poor pretences”; can, I think, only be a corruption of Poa pratensis; the Latin name of the one plant done into English has been fitted to another. The reader will recollect how this grass—more widely known as goose-grass—was sown wholesale over the trough of the run. Nowadays, like scores of other aliens once prominent, it has practically disappeared.

Small-flowered Silene.

Small-flowered Silene.

Each of these seven weeds appeared after fire, though none of them overran, like Silene gallica, hundreds of acres; like Cerastium glomeratum, Hypochæris radicata, Trifolium dubium, and—at a later date—Erigeron Canadensis, thousands of acres. The extraordinary spread of small-flowered silene (Silene gallica), after allowing for its taste for soil of a loose light texture, was due to two especial factors,—one the viscidity of the plant's stalks and stems, the other the nature of the sheep then on Tutira; they were merino, not a bare-legged breed, but sheep, on the contrary, wooled to the toes. Fragments of silene adhering to their shanks were thus carried wherever sheep trod; in the vicinity of “Flower Hill” a single stretch of more than two hundred acres was in 1886 densely covered with silene. In another locality the plant came up at a later date in equal abundance. It is still a common weed alongside pumice paths stirred by sheep traffic, but has elsewhere almost ceased to appear.

Mouse-ear Chickweed.

Mouse-ear Chickweed.

Another fire weed that thrived prodigiously on newly-burnt land was mouse-ear chickweed (Cerastium glomeratum.) Scattered as great healthy plants, though never forming anywhere anything approaching a matted growth, this alien in the height of its page 285 luxuriance grew not over hundreds but over thousands of acres. After fires on the “Staircase” and on the “Second Range” these paddocks assumed in certain lights a strange grey-green hue. It was caused by thistle-down blown from other blocks and lodged in the chickweeds' sticky trails. It also has nowadays become almost a rare plant.

Cat's-ear.

Cat's-ear.

In '85, during a dry season, fire ran over the Image Paddock, destroying the only considerable groves of manuka then growing on the run,—groves perhaps in all some twenty or thirty acres. Throughout this block, especially on the edges of the dead groves, “capeweed” or cat's-ear (Hypochœris radicata) germinated in millions of millions of millions; its seed, blown from the adjoining grassed lands, had been caught by the manuka tops and fallen to earth as the seed of the sow-thistle had elsewhere been trapped by woodland boughs. Whilst the plant was at its zenith, from the hill-tops across the lake I have watched, looking downwards, the phases of a marvellous colour scheme develop, a change from orange-brown, the hue of the tips of the closed blossoms, to the dazzling yellow of the fully unfolded flowers; as the plants began to expand their blossoms, I have even temporarily turned my back on them, the more fully to appreciate the change when viewed again. By nine on a hot dry morning over scores of acres a sheet of gold was spread, a dense bright carpet of colour only possible on land tenanted for the first time by an alien thoroughly appreciative of its environment.

Suckling.

Suckling.

Suckling (Trifolium dubium), though at an early date noted as a plant perfectly adapted to the pumice soils of central Tutira, was nevertheless comparatively slow in taking full possession. It reached success by no short cut, its little seeds were neither blown abroad as thistle, or sow-thistle, or capeweed, or Canadian groundsel, or glued to the legs of sheep like mouse-ear chickweed or silene; it was carried in the stomachs of sheep. Its spread in the centre and west was slow because in page 286 early days those parts of the station were lightly stocked or altogether unstocked; nevertheless, as time progressed, the range of the plant extended until after fires it has become the most important fodder-plant on the station. Unlike the majority of aliens on Tutira, suckling appears and reappears on the same ground more and more thickly. I never look on this insignificant weed without thankfulness: to it I owe my continued ownership of the station; it has produced more wool and saved the lives of more hoggets than any other single fodder-plant on the run. Now that a larger proportion of the pumice soils are open to light and air, its germination, early or late, profuse or sparse, according to meteorological conditions, decides the nature of the coming clip of wool.

After fires in the 'nineties, over central Tutira paddock after paddock was temporarily overrun by Canadian groundsel (Erigeron Canadensis). It also, like other aliens named, has almost completely disappeared.

Spread of plants after fire has, however, been by no means confined to aliens. Readers will recollect that it was as a fire weed that manuka attained its grip of the run; several of the terrestrial orchids, the common catch-fly (Drosera rotundifolia) and Pelargonium australe, have also sprung up and spread after fires, particularly after fires through manuka thickets.

Of late years, too, after fires on rich damp swamp-land, has appeared in profusion Polygonum serrulatum. It is a weed which follows the flax-mill, carried in men's boots, sacking, and machinery.

One weed only on Tutira owes its rapid spread to flood. In the late 'nineties Gillia squarrosa appeared thickly on a sheep-camp on the top of the Image Hill. During the following year the paddock containing that hill was crushed, immense mobs of sheep being run on it, and innumerable new paths stamped out. Then occurred one of the floods which pass at irregular intervals over the station; paths became runnels, runnels became brooks, the Papakiri, into which they poured themselves, rose feet above its banks; everywhere along its course sand was deposited from a couple of inches to a couple of feet. During the following season, on this flood-drift as on tilled soil, germinated masses of the evil-smelling plant, Californian stinkweed it is called, on account of its malodorous savour. Next year it was gone, the following season or two there was a sparse recrudescence of the plant, now it has become a rare weed, appearing only where by chance the surface has been broken and the soil stirred.