Adaptation to cultivation of Hypericum pubescens Boiss., an endangered species in Alentejo (Portugal)

Hypericum pubescens Boiss. is a medicinal plant, classified as endangered species, in the Portuguese red list of vascular flora, mainly due to the intensification of agriculture. This species is widely used in traditional medicine, increasing genetic erosion risk. Thus, studying propagation methods for its efficient cultivation is our main goal. Three seed samples were tested: a) cultivated in 2016; b) from nature in 2017; c) cultivated in 2021. Seed were incubated at 20°C, 12h photoperiod, using 4 replicates. In November 2021, a propagation trial was done using 30 stem cuttings (5 cm length) of four types of cuttings: softwood terminal; softwood sub-terminal; semi-softwood and hardwood. Cuttings were placed in a 5×5 cm cells on trays, using a commercial turf grass substrate. Cuttings rooting success and height was registered after 1 and 2 months. In May 2021, rooted stem cuttings from spontaneous plants were installed in an experimental field, using weed control fabric, constituted by 3 randomized blocks (5 plants block^‑1). Phenology descriptors (flowering dates: beginning, full, end) were observed. In November 2021, agronomic descriptors were observed: plot area, plot biomass production and main stem descriptors (height, length, number of internodes, number of ramifications and biomass production). The germination capacity was maintained after 5 years’ storage in a refrigerator (ca. 5°C). Best seed germination rate was 86%; 1000 seed weight was 0.084 g. The highest survival rate was obtained with sub-terminal cuttings (100%), but softwood terminal cuttings grew faster. On the agronomic plot, average height of plants was 21.9 cm, stem average length was 66.1 cm, thus, plants have prostrate habit; main stems had average of 67 ramifications and 45 internodes. The 4.6 m² plot produced 862.2 g m^‑2 fresh herb and 1.73 t ha^-1 dry herb. Plants were vigorous and cultivation installation using weed control fabric was considered a success.