Ah, polystichums, what a wonderful lot they are. I have never met one I did not like and there are plenty to chose from with more than 200 species and at least 60 hybrids. They are elegant, almost always evergreen, and offer well-mannered har
Polypodium vaccinifolium spreads like a creeping fig on a tree trunk in Trinidad.
mony to the garden's summer and winter woodland composition. The fronds on these tidy plants are frequently shiny and usually have spiny pinnules with a prominent and easily recognized genus-significant auricle (thumb) on the innermost portion of the pinnule(s). On many species and their hybrids, new growth is beautifully trimmed in silvery scales and the crosiers often flip backwards before maturing into uprights.
The genus name, from the Greek poly, many, and stichum, stitches, means "many stitches" in reference to the pattern of the sori that "stitch" the edges of the pinnae. Botanically significant sori have a peltate indusium (round and centrally attached tissue) that opens like a wind-blown umbrella.
Polystichum species are closely related to both Dryopteris and Cyrtomium and were once in a combined classification in the botanical conglomerate Aspidium. Like Dryopteris, they are heavily decorated and botanically differentiated by stipe and rachis scales in assorted colors, shapes, and sizes. While they do not have independent hairs, some of the scales may have hairs (splitting hairs botanically here, if you would). When fertile fronds are present, polystichums can readily be differentiated by their peltate indusia rather than the kidney-shaped indusia of dryopteris. Cyrtomiums share the peltate indusial characteristic but have easily observed netted veins rather than the free veins of polystichums.
Most polystichums are considered horticulturally hardy (which means temperate rather than "easy" as in some interpretations). They range from temperamental alpines, requiring specialized site preparation and maintenance, to stately and reliable garden ornamentals. Eastern North America and Europe are poorly represented with limited numbers of species, although Britain contributes a significant complement of cultivars. For promising hardy introductions, Japan, China (the capital of the fern world for once-pinnate polystichums), and the Himalayas have provided Western gardens with an abundance of ornamental offerings with the potential for yet more discoveries to come. Some of these may be difficult to establish in hot and humid summer climates, but with so many options, all are worth introducing to gardens— at least once.
Unless otherwise noted all of the polystichums described here like light shade and a regularly watered, moist but not wet site. Most will adapt in friable acid to neutral soil. Although all three British species, Polystichum aculeatum, P. lon-chitis, and P. setiferum, are native to basic soil sites, they do not require them. The challenging alpines require good air circulation, excellent drainage, and fresh as opposed to stagnant water. They are accustomed to wintering under snow and usually are not long-lived at lower elevations. Please do not try to collect them. Enjoy them instead in their mountain habitats where they delight the horticultural hiker and are in harmony with their surroundings.
A number of species and some hybrids produce bulbils on their frond tips or, as in the British Polystichum setiferum and many of its cultivars, along the entire proliferous rachis strip. Propagation is easily accomplished by pinning these down onto soft soil. In addition the proliferous buds can be surgically removed from the parent plant and encouraged in the
A collection of evergreen polystichums offers year-round formal elegance in an entryway woodland planting.
Young crosiers of polystichums are elegant with their silvery coats as seen here on a Polystichum munitum hybrid.
accommodating climate of a humid mini-greenhouse. An inverted clear plastic cup over a 4-in. (10-cm) pot works nicely. Firm the bud onto the surface of the soil and place it in good light but not direct sunshine.
Spores are in most cases the only propagation option for the exotics. Germination tends to be erratic and more study is needed to determine optimum conditions for producing reliable and consistent crops. I have found that spores sown promptly from late season rather than early summer fronds tend to reproduce in better percentages.
Finally, since these are evergreens, I am frequently asked whether or not to trim off the old fronds. It is certainly the tidy thing to do, but leaving them on enriches the soil naturally and produces larger plants in ensuing years. If fronds are to be removed, it is easiest to attack the old foliage with one whack before new growth emerges in the spring.
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