PlantLife Volume 50.4 December 2020. A new species of Hesperantha

 A new species of Hesperantha discovered in the Umtamvuna Nature Reserve

Text by Kate Grieve, Photos by Graham Grieve

The Umtamvuna Nature Reserve is home to many Pondoland endemics and the newest of these is Hesperantha mtamvunae, recently described in the new Iridaceae publication (see the review in this edition of PlantLife).

 

Hesperantha mtamvunae

On regular outings of the Pondoland CREW group to the Umtamvuna reserve in the past few years, occasionally we noticed a tall, elegant, pink Hesperantha and wondered what it was.  It seemed slightly different from other more familiar members of the genus and flowers in late winter or early spring (June to July), whereas the others flower in summer.  Hesperantha grandiflora is similar in appearance but only occurs at higher altitudes (between 1600 and 3000 m) and flowers in late summer (January to April). The most common Hesperantha species in the Umtamvuna reserve is H. baurii.  It also a slender plant but the inflorescence has a characteristic zigzag stem and the flowers are deep pink.  It grows in open grassland and flowers from November to February.  The other species seen regularly at Umtamvuna is H. hygrophila but it has white flowers and generally grows en masse on damp rocky ledges, flowering in late summer.

 

The brown anthers are a distinguishing feature of the species.

Hesperantha mtmvunae being visited by a pollinator

For the citizen scientist, the thought of identifying Hesperantha species is rather daunting and so the plants remained unidentified for some years.  However, my curiosity got the better of me and in 2017 I collected a specimen of the plant in flower and sat down with the key, determined to establish its identity.    The key took me to H. woodii, a species that only occurs inland at higher altitudes, the distribution indicating that the Umtamvuna species was unlikely to be H. woodii.  I then sent an email with photographs to John Manning at the Compton Herbarium at Kirstenbosch, asking for his opinion.  John requested measurements and voucher specimens, initially suggesting that it was a form of H. grandiflora.  However, a few weeks later another email arrived from John with the news that he and Peter Goldblatt had decided it was a new species, much to our excitement.  The next request was for fruiting material, no easy task since the plants grow in long grass and the slender stems are difficult to see, particularly without flowers.  This required a special trip to a northern section of the reserve and a walk through the grassland to the steep slopes where the voucher material was collected. Fortunately we were able to find plants with fruits containing seeds and these were dispatched to Compton Herbarium. 

 

Fruit capsules on Hesperantha mtamvunae

Seeds of Hesperantha mtamvunae (blocks are 2mm by 2mm)

Time passed and we looked forward to seeing the name of our plant in the new Iridaceae book, with publication expected early in 2020. March marked the much anticipated availability of stocks of this new publication, but this coincided with the restrictions of the strict Level 5 lockdown as a result of COVID-19 and with it, the closure of the post offices. It took the kindness of a friend in Pretoria who collected the weighty tome from SANBI and took it to Postnet before I could see the end result of our search.  Finally Hesperantha mtamvunae had arrived.

H. mtamvunae is one of the long-tubed species of Hesperantha, the perianth tube being up to 25 mm long and straight or slightly curved.  It is unusually tall, between 500 and 750 mm, with two upright basal leaves reaching approximately the same height. Like many other Hesperantha species, the flowers are mauve-pink with a yellow throat but features that distinguish this species are the distinctive brown colour of the anthers and the number of flowers (3 to 6) in a spike.  It grows on damp or cooler steep SE-facing slopes in open grassland and woodland margins on Msikaba sandstone.  There are several sub-populations within a section of the reserve but to date it has not been found elsewhere.

 

Typical habitat for Hesperantha mtamvunae; fairly steep, south-east facing grassland slope, on Msikaba sandstone.

 

About the author: Kate Grieve recently moved to a new home near Scottburgh on the KZN south coast and continues to pursue the CREW mandate.  Her passion for indigenous plants is also expressed in botanical art.