2024 Articles:
We conducted a three-year study at the University of California Research and Extension Center in Irvine, California on the effect of the plant growth regulator paclobutrazol on the growth of seven species of common landscape shrubs. The shrubs were in 3.8 l standard nursery containers. We randomly arranged and planted four plants each of Bougainvillea ‘Raspberry Ice’, Escallonia × exoniensis, Nerium oleander, Pittosporum tobira, and Rhaphiolepis indica and two plants each of Buxus japonica and Photinia × fraseri in a row. We included six replicate rows in the study. We placed the plants 2.1 meters apart in a row and spaced the six rows 3.7 meters apart. We randomly applied four treatments to the five species with four plants in each of the six rows: a control (no treatment) and low, medium, and high amounts of diluted ready-to-use (RTU) paclobutrazol (1 part Shortstop® 2SC concentrate to 11 parts water). We randomly applied two treatments to the two species with only two plants in each of the six rows: a control and medium amount of diluted RTU material. We determined the amount of diluted RTU material to apply to each plant by each plant’s crown volume and whether it was a low, medium, or high rate. Paclobutrazol tended to reduce growth across all seven shrub species at any rate 4 and 13 months after treatment. At the end of the study, 23 months after treatment, none of the treatments significantly reduced growth compared to the control. Paclobutrazol significantly reduced plant appearance across all seven species at any rate at 4, 13, and 23 months after treatment. The reported effects of paclobutrazol, including reduced shoot elongation, shorter internodes, more compact growth, and disease resistance tended to be true in our study. However, other reported effects, such as normal sized and darker green leaves, did not occur in most cases in our study; leaves tended to be smaller on treated plants while only Buxus japonica had greener leaves on treated plants. Suspected phytotoxic responses, mostly leaf discoloration, deformation, marginal chlorosis and necrosis, and defoliation leading to canopy thinning, were present in over half the species. https://doi.org/10.21414/B1301Z
Schinus molle, the California pepper tree, is one of the most iconic trees in the State's landscape and well adapted to its ever-heating, -drying, and increasingly arid climate. Unfortunately, a new and serious malady causing canopy thinning and dieback and even tree death has appeared in the last several years. Here, we discuss the host tree and provide the history and suspected causes, symptoms, and potential management strategies for canopy thinning. https://doi.org/10.21414/B16P4X
Two new species of Basselinia and a new variety of Chambeyronia divaricata are described, illustrated, distinguished from related species, and their history, ecology, and conservation status discussed. https://doi.org/10.21414/B1BC76
The mite Brachytydeus formosus, the disease caused by Botryosphaeria sp., and the abiotic stress of improper irrigation (excessively moist soil and/or perhaps even prolonged drought) can now be added to the leafhopper Empoasca sativa as possible causal agents of Schinus molle canopy thinning. It seems probable that any one of these factors is not acting alone but that two or more are acting in combination. A likely scenario is that excessively wet soil or prolonged, consecutive years of drought could not only stress trees and lead to canopy thinning on its own but could initiate or predispose trees to disease (Botryosphaeria sp.) and pests (E. sativa and B. formosus). Also, improper soil moisture could enhance pest and disease damage, making them more severe than they would be on a healthy, stress-free tree. https://doi.org/10.21414/B1G594
Anthurium anomalum (Araceae), a new species in sect. Urospadix, subsect. Obscureviridia from cultivation, is described, illustrated, compared and distinguished from similar species, and its cultivation discussed. https://doi.org/10.21414/B1KW2N
Collectors Humboldt and Bonpland in 1801 and Poeppig in 1823 made the first five collections of palms in Cuba. Based on these collections, Kunth in 1816 and Martius in 1838 provided the first names and descriptions of Cuban palms. Here, the taxonomy, nomenclature, and status of these names and descriptions are reviewed and updated. The type locality of the corojo of Cuba is verified. https://doi.org/10.21414/B1QP4K
Eight species of indigenous palms are reported for El Salvador. We base this finding on bibliographic information, websites, research projects, consultations with Arecaceae specialists, and review of material deposited in various national herbaria, including LAGU (Jardín Botánico La Laguna), MHES (Museo de Historia Natural de El Salvador) and TECLA (Banco de Germoplasma de El Salvador). We provide Information on nomenclature, synonyms, species descriptions, distribution, phenology, habitat, conservation status, and ethnobotany of the indigenous species of El Salvador. We also provide a key to the species, distribution maps, tables, and photographs as supporting documentation. We highlight Brahea salvadorensis as the only palm species originally described in El Salvador. Finally, we list and discuss additional palm species previously thought to be indigenous but now no longer considered so and exotic species. https://doi.org/10.21414/B1VC7V
Osa pulchra (Rubiaceae), a rare and endangered shrub to small tree from Costa Rica and Panama, is described and illustrated, and its history and cultivation, including propagation, are discussed. https://doi.org/10.21414/B1059S
Early-season, height-reduction pruning of Lantana strigocamara ‘Balandrise’ (LuckyTM Sunrise Rose) to 15 cm tall to assess whether plants could be maintained low and compact without loss of flowering performance had significant but mixed results. Pruned plants eventually grew taller and had more shoots with longer internodes but shoots initially were shorter and required more leaves before flower initiation while unpruned plants had fewer but initially longer shoots with shorter internodes and more leaves. On unpruned plants, lateral shoots were longer and had more leaves and longer internodes but required more leaves before flower initiation than tip shoots. The results suggest that early-season pruning can be initially growth limiting but growth invigorating later yet did not result in low, compact growth and enhanced flowering. https://doi.org/10.21414/B13W29
The taxonomy of palm (Arecaceae) collections in Cuba carried out by Sagra or collaborators, some of them published by Richard in 1850, is discussed and updated. Here, ten species, nine of them indigenous or endemic and belonging to seven genera, are identified. Sagra’s collections are present in seven herbaria. https://doi.org/10.21414/B17P47
The history of the introduction and early cultivation of the date palm (Phoenix dactylifera) (Arecaceae) in Hawai’i is discussed, illustrated, and analyzed. Some of the original or early introductions are still present in the landscape. https://doi.org/10.21414/B1CC7H
The neotropical genus, Rhodospatha, is completely revised with 136 recognized species. It follows the just-published revision of the genus for Central America (Croat & Delannay 2024). A total of 91 new species are described here. Species are fully described, compared, and illustrated. A dichotomous key is included here and a separate Lucid Key has been prepared and will be published later online.