Flora of New Zealand Series

browntop

Loose to dense perennial tufts to c. 100 cm, often forming a dense turf or loose sward, spreading by very short rhizomes; branching intra- and extravaginal, the intravaginal shoots erect or sometimes decumbent or forming trailing stolons, the extravaginal shoots subterranean, bearing pale scale-leaves. Leaf-sheath glabrous, greenish to purplish. Ligule 0.6-2 mm, truncate to rounded, in non-flowering shoots shorter than wide. Leaf-blade (1.5)-2-13-(15) cm × 1-2.5-(5) mm, flat or ± involute, ± scabrid, acute. Culm erect or geniculate, often procumbent and branching then erect or ascending, sometimes remaining ± horizontal, internodes usually smooth, rarely scabrid below panicle. Panicle 2-15-(28) cm, oblong to ovate or pyramidal, usually very lax with many spreading branches; rachis smooth or sometimes scabrid above, branches and pedicels smooth or slightly scabrid. Spikelets 1.5-3.5 mm, purplish brown to greenish. Glumes subequal, lanceolate, acute; lower slightly scabrid above on midnerve, upper smooth. Lemma 1.5-2.5 mm, smooth or sparsely scabrid, ovate or elliptic, obtuse or truncate, 3-nerved with marginal nerves sometimes slightly excurrent and midnerve not usually reaching lemma tip, or rarely 5-nerved with midnerve produced to an awn arising middorsally and occasionally geniculate and projecting slightly beyond tip of lemma. Palea usually ½-⅔ length of lemma, apex usually bifid. Callus glabrous or with very short hairs. Anthers 1-1.5 mm. Caryopsis c. 1 × 0.4 mm. Plate 3B.

N.; S.; St.: common throughout; Ch., A., C. Sea level to subalpine in disturbed ground and in modified grassland.

Naturalised from Eurasia.

Throughout the world and for many years Agrostis tenuis Sibth. was accepted as the correct name for browntop.

Browntop is a notoriously variable sp. with plants differing in size, habit, presence or absence of stolons or rhizomes, type of inflorescence, and in spikelet structure. It is widespread in pastures of several kinds in N.Z. and a standard component of lawn mixtures. Some of the variation may arise as a result of hybridisation with related spp.

Forde, M. B. in Edgar and Forde (1991 op. cit.), confirmed that where A. capillaris and A. castellana coexist a blurring of the boundaries between the spp. has already occurred and will continue, with characteristics of A. castellana remaining in populations of A. capillaris. However, the difference of two weeks in flowering time between the two spp. may restrict the formation of F1 hybrids and, once formed, these hybrids will most likely backcross repeatedly to A. capillaris, the dominant sp.

Lee, W. G., Mark, A. F. and Wilson, J. B. N.Z. J. Bot. 21: 141-156 (1983) reported their experiments on an ultramafic ecotype of A. capillaris (as A. tenuis) at Black Ridge, Southland. Rapson, G. L. and Wilson, J. B. Functional Ecol. 2: 479-490 (1988) found very little evidence of adaptation of populations of A. capillaris sampled from a wide range of habitats in southern South Id and transplanted back into their own and each other's sites.

Plants of browntop infected by smut fungus, Tilletia sphaerococca, are dwarfed and tufted, with small compact panicles, undulating panicle branches, and glumes often shorter and broader than usual. Plants in which the eelworm Anguina agrostis had formed galls in the spikelets and caused elongation of glumes and lemmas were recorded by Healy, A. J. N.Z. J. Agric. Res. 1: 265-266 (1958).