Effective ex situ conservation of plants in botanic gardens requires sufficient wild accessions to represent wild diversity. In Rhododendron L. (Ericaceae), c. 64% of the taxa are threatened or require field investigation. As a case study of the analysis of ex situ conservation gaps we used ecogeographical representation as a proxy for genetic representation in ex situ collections of the 65 taxa of Rhododendron subsection Maddenia. We compiled the first list profiling both wild distributions and ex situ wild collections of all taxa in subsection Maddenia. Our results reveal that 55 Maddenia taxa are in cultivation. Of the 18 threatened taxa all are in cultivation but nine require further collection to capture adequate wild diversity. There are 12 Data Deficient taxa: these await further field investigation of wild populations and nine of them require wild collections to conserve genetic diversity. The UK, the USA, Australia, New Zealand and China are the top five countries holding ex situ collections of subsection Maddenia; in these countries nearly 66% of the ex situ sites hold > 86% of the global living collections of subsection Maddenia. We recommend that wild collections of endemic species of subsection Maddenia should be established in all 10 countries of origin and that data should be shared internationally for metacollections. In addition to proposing priorities, our case study highlights the challenges facing data and collection management to help achieve effective ex situ conservation for Rhododendron species.

A biographic summary of the research of Dr Graham Charles George Argent (born 15 May 1941, died 24 April 2019) is presented, summarising his research career. Expedition information, including dates, collection number series and the names of collaborators, is given, as is a list of his publications, annotated with taxonomic decisions and the names of new species described within them.

Metolachlor, oryzalin, and napropamide when chemigation-applied controlled large crabgrass more effectively than when spray applied in container-grown azalea, liriope, and Japanese holly. Oxadiazon and oxyfluorfen were equally effective as chemigation or spray applications. Azaleas were generally more susceptible to contact injury from sprays of oxadiazon and oxyfluorfen and large crabgrass interference than were holly and liriope.

Rhododendron stanleyi S.James & Argent is described as a new species from Mount Yule, Central Province, Papua New Guinea. Its morphological position in the subgenus is discussed and the differences given from the most closely similar species. A note on the habitat and conservation assessment is also provided.

A new species, Rhododendron pseudomaddenii A.A.Mao & M.Bhaumik (Ericaceae), is described and illustrated from India.

The new species Rhododendron mechukae A.A.Mao & A.Paul (Ericaceae) is described from India.

The new species Fellhaneropsis rhododendri is described from living Rhododendron leaves in the Netherlands. It is characterized by pyriform pycnidia with stiff, septate hairs at the mouth. It is doubtlessly due to recent global warming that an obligately foliicolous lichen can be described from a temperate area in Europe.

The orchids Dendrobium infundibulum and Cymbidium insigne are pollinated by the bumblebee Bombus eximius, which also pollinates the ericaceous shrub Rhododendron lyi, A study of the three plants and the bumblebee in maquis-like mountainous vegetation in northern Thailand suggests that they form a floral mimicry system with two mimics (the orchids) to one model (R. lyi). The flowers of the two orchid species offer no food reward to pollinators. Flowers of the three species show definite morphological and visual resemblance, and the species overlap to a great extent in flowering phenology and habitat Mimic flowers were much less numerous than model flowers, which occurred abundantly in the area. The rate of pollinaria removal was very low in both orchid species, resulting in a relatively small percentage of fruit set, especially in D. infundibulum. Infrequency of pollinator visits was, however, somewhat counterbalanced by long-lasting flowers. The pollinaria of the two orchid species are differently positioned on the bee, hence interference between the different reproductive systems is minimized. This is the first report which indicates floral mimicry from tropical Asia.

Rhododendron subgenus Tsutsusi (Rhodoreae, Ericoideae, Ericaceae), commonly known as evergreen azaleas, includes approximately 117 deciduous and evergreen species from Japan, China and northeastern Asia. Subgenus Tsutsusi has been divided into two sections, Brachycalyx and Tsutsusi, based on characteristics of the leaves, young twigs and corolla. We obtained molecular data from three chloroplast (matK, ndhF and trnS-trnG) and two nuclear (nrITS and the third intron of rpb2) regions for 30 species of Rhododendron subgenus Tsutsusi and five species of Menziesia. Parsimony, Bayesian and likelihood analyses based on total evidence were used to assess the monophyly of the sections within Rhododendron subgenus Tsutsusi and relationships among the species sampled. In particular, the placement of the problematic Rhododendron tashiroi was addressed. Results support Rhododendron tashiroi as a member of the Rhododendron section Brachycalyx clade. Molecular evidence also supports a clade within Rhododendron section Tsutsusi containing R. indicum, R. tsusiophyllum, R. tschonoskii and R. serpyllifolium, species which were not previously considered closely related.

The flowering phenology of five alpine dwarf-tree species was observed in the summit region (3900–3950 m elevation) of Mt. Kinabalu on Borneo Island from March 1998 to November 2001. For each target species, 20–50 individual plants were numbered in two observation plots and the number of inflorescences was monitored at 2–3-mo intervals. The flowering patterns varied among species. Rhododendron buxifolium bloomed extensively every March–May at the main plot but the flowering pattern at the subplot was less predictable. Mass flowering occurred in March 1998 when drought stress was very severe due to an El Niño event. Rhododendron ericoides showed continuous flowering throughout the year and high synchrony between the plots. Extensive flowering of Leptospermum recurvum occurred synchronously within and between plots in the early half of 1999, then flowering activity decreased greatly. Photinia davidiana showed an annual flowering cycle but the timing of the peak flowering differed between the plots. Vaccinium stapfianum showed synchronous flowering between the plots and the flowering peak appeared at longer than 1-y intervals. Plant size was positively correlated with mean flower production in all species, and with the flowering frequency of R. ericoides, R. buxifolium, and V. stapfianum at one of the plots at least. Two fleshy-fruited species, P. davidiana and V. stapfianum, had high selfing ability for fruit production and showed relatively low flowering synchrony among individuals in comparison with the other species. These results indicate that the trigger for initiation of flowering may differ among sympatric species in a tropical-alpine ecosystem at least in normal years.