Eleocharis geniculata

Eleocharis (Cyperaceae) is a large genus comprised of about 200 species. Most of them are widely distributed in the tropical and subtropical regions over the world. Their very broad geographical range might probably attribute to wind-pollination and wind-dispersal mechanisms, which are particularly efficient in open and windy habitats that most of the members inhabit. No leaf blade can be found in the genus where only shealth is present which is a major characteristic for the genus.

Eleocharis geniculata is uncommon in Hong Kong. Their abundance might be confined by limited suitable habitat which mainly inhabit coastal wetlands. Identification of it is easy by identifying three major characters:

1. Spickelets are broader than culm (shown in 1st photo);
2. Stigma is bifid (shown in 3rd photo);
3. Nuts are blackish, of about 1 mm long with 6-8 hypogynous bristles (shown in 3rd photo).

Scleria lithosperma [misidentified as Scleria biflora]

The above specimen is more likely Scleria lithosperma than S. biflora. After checking a bunch of literatures I found that nuts of S. biflora should be globose, regularly cancellate and beaked with black/purplish persistent style base. It is obviously wrong for the above specimen which is having obtusely trigonous, smooth and shining nuts. Both species could have simple inflorescence which is originally thought not the case for S. lithosperma.

I here keep the original message of S. biflora. However its status might not be correct:

Scleria biflora (Cyperaceae) is most likely the smallest Scleria species in Hong Kong. Inflorescence only bears one or two florets which gives its scientific name biflora. It is quite common in Hong Kong which can mainly be found in forest edge, shrubland or path side. However, the inflorescence or nuts are too inconspicuous which might usually be overlooked. It is also difficult to photograph where the above pictures are heavily cropped in order to show its inflorescence and nuts.

Fimbristylis cymosa

Fimbristylis cymosa (Cyperaceae) is one of the commonest Fimbristylis species seen in Hong Kong especially in the coastal or sandy shores. The height of the plant can be varied quite much which is ranged from about 10 to 40 cm. It has a compound inflorescence with relatively small spickelets. I roughly measured over 10 spickelets from several individuals and most of them are about 3 mm. One of the easiest way to distinguish this species from many other Fimbristylis is that it produces blackish nuts which gives its Chinese name "黑果飄拂草" (literally means black-nut Fimbristylis). Though some publications stated that its stigma is either bifid or trifid, so far I could only find the bifid one but none of them are trifid. I will correct myself if I did find the latter.

Rhynchospora corymbosa

Rhynchospora corymbosa (Cyperaceae) is a globally distributed species which is reported to be found in tropical and subtropical regions. However it was previously assessed as rare in Hong Kong which can only be found in a few localities. The above individual was found in an undescribed locality which is only holding a few individuals. It mainly inhabits lowland wetland or streamside which is, therefore, very vulnerable to disturbance, channelization, development and pollution. There is indeed quite a lot of wetland-associated species in Hong Kong so it's important to take care of this habitat in order to conserve this diversity.