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Classification, origin and description
Common name: Polisticum.
provenance: areas with a temperate or tropical climate.
Genre description: includes about 135 species of terrestrial ferns (for the most part) or epiphytes, which have rigid fronds, leathery consistency, often evergreen, with pinnules almost always indented. It includes species suitable for outdoor and greenhouse cultivation.
Polystichum webbianum (Berlin Botanical Garden) (photo website)
Species and varieties
Polystichum acrostichioides: native to North America, this species, suitable for outdoor cultivation, has dark green pinnate fronds, which, at the juvenile stage, are covered with white and shiny scales. The lower page of the highest fronds can be almost completely covered with sporangia. It grows up to 1 m. tall and 60 cm. in diameter.
Polystichum aculeatum: native to Europe, Europe and North America, this fern, suitable for outdoor cultivation, has glossy green fronds, leathery consistency, lanceolate, pinnate, with deeply divided pinnules. The main stems and ribs are covered with brown scales. It grows up to 60-100 cm. in height. Among the best known varieties we find: "Gracillimum", with delicate fronds divided into filiform pinnules, which reaches one meter in height and diameter, suitable for the cold greenhouse; "Pulcherrimum", sterile variety of the same size as the previous one, with silky fronds, with elongated pinnules that are gathered in tufts at the end, suitable for outdoor cultivation.
Polystichum falcatum: native to Japan, China and Himalaia, this species has dark green and shiny pinnate fronds, formed by lanceolate pinnules, with toothed margins and a sharp apex. It grows up to 50-100 cm. in height and diameter and is suitable for growing in apartments, even in less than optimal conditions. Among the varieties on the market we find the "Rochfordianum", of reduced size (30-45 cm. In height and diameter) with pinnules twice the size of those of the typical species.
Polystichum lobatum: native to the forests of Europe, this species with shiny, leathery, semi-persistent and double the length of the width is suitable for cultivation in the garden.
Polystichum lonchitis: this evergreen fern, which is also suitable for cultivation in calcareous soils, has very decorative leathery fronds. The variety "Cristatum" is perhaps more widespread than the type species.
Polystichum munitum: native to North America, this garden species has fronds with linear pinnules with toothed margins. It reaches one meter in height and diameter.
Polystichum setiferum: this garden fern comes from the temperate and tropical climate regions, from the evergreen, double-plotted fronds, which, at the juvenile stage, are covered by white or light brown scales. It can grow up to 50-100 cm. in height and 1-1.5 m. wide. Among the most significant varieties we find: "Acutilobum", characterized by the possibility of producing bulbils along the main rib of the branches, formed by pointed and bristly pinnules at the end which tend to become prostrate during the winter; "Divisilobum", from the large arches to the juvenile stadium and prostrate during the winter, three-year-old at the base and two-year-old at the end, which can reach 1.5-2 m. in diameter; "Plumoso-divisilobum", with four-plucked, overlapping and deeply divided branches; "Proliferum", with expanded growth habit, which produces new small seedlings on the upper page of the adult foliage.
Environmental requirements, substrate, fertilizations and special precautions
Temperature: the minimum winter temperature must remain around 8-10 ° C.
Light: good, away from direct sunlight.
Watering and environmental humidity: water abundantly in spring-summer; reduce doses in autumn-winter, taking care to keep the substrate just moist.
Substrate: based on garden soil, leaf and peat soil, with the addition of sand. From May to September, administer liquid fertilizer monthly. Repotting takes place every two to three years.
Special fertilizations and tricks: greenhouse and apartment Polystichums are grown in 15-18 cm pots. in diameter. The species suitable for outdoor cultivation are planted in March-April in preferably calcareous soil, in a shaded position. They are very afraid of drought and, in hot weather, it may be necessary to water them abundantly.
New specimens can be obtained by division of the rhizomes in March-April. Another method of multiplication consists in planting, in September-October, the leaves with bulbils in a mixture of peat and sand, in bowls or trays. After rooting, they are transplanted into pots filled with the same substrate used for adult plants.