Polystichum (Class: Filicopsida, Order: Polypodiales), or
shield ferns, as they are commonly called, is a genus of 160 to
200 species. They occur throughout the temperate parts of the world
as well as the montane tropics, but are mostly absent from the lowland
tropics. There are two distinct centres of diversity; a larger Asiatic
centre and a smaller tropical American centre. Both these regions
fall within the mountainous tropics characterized by mild, moist
climates that are hardly seasonal.
Polystichum is generally considered closely allied to Dryopteris,
the wood or oak ferns. Shield ferns are characterized by having
1-pinnate to 3-pinnate leaves, which are more developed on the upper
side of the pinna-rachis or mid-vein than it is on the underside.
They also have shield- or umbrella-like indusia protecting the developing
sporangia. In a number of species, however, the sori lack indusia.
Polystichum species mostly occur on the ground, but often
also on rocks. They can be divided into two groups; the first has
short erect, mostly unbranched rhizomes, sheathed by closely spaced,
persistent stipe bases, whereas the second group has longer, prostrate
rhizomes, which are frequently branched and the leaves more widely
The rhizomes, like the leaf axes, always bear chuffy scales which
become abraded as the leaves grow older. The leaf stalk and main
leaf axes are always channelled on the upper side. Depending on
the species, the leaves are 1- to 3-pinnate. The leaflets on the
upper side of the pinna mid-vein and closest to the lamina axes
are always longer and eared. The leaflet margins are mostly strongly
toothed and often end in an elongated spine-like tip.
sporangia are borne in round sori, mostly situated in two rows on
the underside of the leaflets. When young, the sori are protected
by centrally attached or umbrella-shaped indusia, which become shrivelled
and darker in colour as they mature. Within each sporangium, 32
or 64 dark brown to blackish spores are formed.
Polystichum is poorly represented in Africa with only 17
species recorded. They are all confined to the eastern mountainous
regions of the continent with the Drakensberg being the centre with
the highest diversity. Some species occur from near sea level, others
are confined to higher elevations, often extending up to 3 000 m.
Name and history
Polystichum is derived from the Greek word poly meaning
many and stichos meaning order or rows. This probably refers
to the arrangement of the sori on the leaflets.
Shield ferns mostly occur in seasonally moist, evergreen forests,
but at high altitudes the plants are generally confined to rock
crevices and shaded cliff bases. In these harsh conditions the plants
are often exposed to fires and snow. Since the rhizomes are mostly
subterranean these events generally have little effect and plants
re-grow rapidly. In spite of the low temperatures some species are
exposed to, none of the Africa species are seasonally dormant. New
fronds are generally produced at, but not restricted to the onset
of summer, especially after the first summer rain. Reproduction
is either through spores or by rhizome division. The latter feature
generally results in the plants forming clonal stands.
Economic and cultural value
Polystichum species, and in particular variations and sports
of some European species were highly sought after during the Victorian
fern craze in the late 19th century. There were 366 named forms
of P. setiferum alone. Many of these cultivars are unfortunately
now lost. A limited number of shield fern species are available
in local nurseries, mostly as house plants. They unfortunately have
not become popular garden plants.
Rhizomes of various shield fern species have been used since the
18th century as a cure for intestinal worms. Also the Zulu use a
decoction of rhizomes from various Polystichum and Dryopteris
species as a general anthelmintic.
In the Garden
Several South African shield fern species are suitable for cultivation
in the moister parts of the country. The suitable species are discussed
below. Since none of them are exceptionally large, they are ideal
for the smaller garden. For successful cultivation a few basic requirements
must be met:
- Shade: All the species require light shade, especially
during the warmer parts of the day. Direct sunlight in the mornings
or late afternoon is generally not a problem once the plants are
well established. It is also best to protect plants against strong
- Moisture: Ferns have shallow root systems and the soil
must therefore be kept moist at all times. This is especially
important while the plants are still young and not yet fully established.
Maintain soil moisture by mulching. Also ensure that adequate
humus is worked into the soil before planting. Ferns in general
do not require a special feeding program, but if additional plant
food is provided they are quick to respond.
South African shield fern species suitable for
incongruum: forest shield fern (Eng.); woud skildvaring (Afr.)
This species is confined to the Western and Eastern Cape in South
Africa, occurring at elevations ranging between 600 and 1 350 m.
Although it mostly occur in forests it is not confined to them,
often forming large stands on road cuttings. As a result of the
decumbent and branched rhizome, the species has a shrub-like growth
form, reaching a height of up to 0.8 m. The leathery dark green,
erect to arching leaves may reach a length of up to 1.8 m, and can
be up to 3 times divided. The species is best cultivated in moist,
shaded conditions, although it will tolerate some sun once well
established and the growing medium is kept adequately irrigated.
Propagation is best done by rhizome division.
luctuosum: mourning shield fern (Eng.); treur skildvaring (Afr.)
The species has a wide distribution in the Old World, extending
as far as Japan. It is also widely distributed in South Africa,
occurring from the Eastern Cape through KwaZulu-Natal to the northeastern
parts of the Free State, Mpumalanga and the Northern Province. It
grows at elevations ranging between 760 and 1 740 m. The species
is confined to evergreen forests where it grows on the forest floor
or on rocks. P. luctuosum is often sold as P. tsus-simense
and is a predominantly single-stemmed species resulting in a tussock-like
growth. It can reach a height of up to 0.4 m. This smaller species
has a very neat appearance, and is characterized by the almost black
scales and dark veins, which contrast with the olive-green leaves.
It is best cultivated in shade and needs to be kept moist, but not
wet, at all times. It is a slow grower. Propagate by spores.
macleae: McLea's shield fern (Eng.); oostelike skildvaring (Afr.)
Polystichum macleae is confined to the Drakensberg Escarpment
and Wolkberg in Mpumalanga, occurring at elevations ranging between
1 350 and 1 960 m. It usually occurs in evergreen forests, but at
higher elevations it is also found in the lee of large boulders.
As a result of the decumbent, sparsely branched rhizome, it often
forms small clonal stands resulting in a shrubby growth form. This
is the only South African species with 1-pinnate leaves. They are
mid- to dark green and can grow up to 1.5 m long. This very attractive
species is worthy of cultivation. The species is best cultivated
in light shade and requires permanently moist conditions. Propagate
by rhizome division.
monticola: mountain shieldfern (Eng.); berg skildvaring (Afr.)
Polystichum monticola is confined to South Africa, extending
from the Kamiesberg in the Northern Cape, through the Western- and
Eastern Cape, KwaZulu-Natal and the Free State, to Lesotho, occurring
from 600 to 2 740 m. The habitat includes seasonally moist, evergreen
forests, rock crevices, cliff bases, stream banks, and forest margins,
often growing in exposed, seasonally xeric conditions. The rhizome
is decumbent and closely branched, resulting in plants forming a
shrubby growth form. This variable and predominantly high altitude
species is ideally suited for garden cultivation. The arching leaves
are mid-green in colour and up to 0.8 m long. Although the species
will tolerate some sun once well established, it is best cultivated
in moist conditions in light shade. The species is slow growing
and propagation is best done by rhizome division.
pungens: forest shield fern (Eng.); woud skildvaring (Afr.)
Polystichum pungens is restricted to South Africa and Swaziland.
In this region it ranges from Table Mountain, along the southern
mountain ranges, and the Drakensberg foothills to the Wolkberg in
Mpumalanga. It occurs at elevations ranging from 600 to 1 350 m
and is restricted to forests. The rhizome is decumbent and regularly
branches, resulting in the plants forming clonal stands and a shrubby
growth form. The leathery leaves can be up to 1 m long, are dark
green and suberect to arching. The species is best cultivated in
moist shaded conditions, but will tolerate morning sun once well
established. Propagate by rhizome division.
transvaalense: stemmed shieldfern (Eng.); enkelstam skildvaring
Polystichum transvaalense is widely distributed in temperate
and tropical Africa. In South Africa it occurs from the Drakensberg
foothills in the Eastern Cape along the KwaZulu-Natal Drakensberg
escarpment, the Eastern Cape and southern KwaZulu-Natal midlands,
the Free State-KwaZulu-Natal and Mpumalanga-Limpopo Province escarpment
to the Soutpansberg, with outlying populations in the southern Cape
mountains. It occurs at altitudes ranging from 365 to 1 840 m and
is confined to forests. It has a short erect, usually unbranched
rhizome and a tussock-like growth form. In suitable conditions the
suberect to arching pale- to mid-green leaves may be up to 1 m long.
The species is suited to be used as a focal point in smaller gardens
and should best be cultivated in light shade, preferring moist conditions.
The species is worthy of cultivation because of its neat appearance.
Propagate from spores.
Compton Herbarium, Kirstenbosch