Download Article 123 Arundo donax Spanish Reed

Weeds in our Area (Part One Hundred and Twenty Three)
By Bob and Ena McIntyre – Garden Route
Arundo donax (Spanish Reed, Giant Reed, Spaans(e)riet)
Revisiting some of our old enemies at this time every year helps to refresh the memories of our
visitors and those homeowners who return for their holidays. Strolling along the road to Fairy
Knowe one simply cannot ignore the well-established stand of Arundo donax (Giant Reed variegated colour version) alongside the tarmac. The species originates from the Mediterranean
region but has been introduced worldwide into countries with a suitable climate. In ideal
conditions A. donax is extremely invasive and fast growing. Research shows that the species can
grow up to 5cm a day and reach its mature height of ±6 meters within one year. Despite this,
during the 1980’s it was recommended as a “striking evergreen for the large garden……..” More
advice along these lines was to cut old stems back to ground level to “encourage new, vigorous
growth” to produce larger and more richly coloured foliage.
To its credit - A. donax has numerous uses: A bio-fuel that produces methanol from gas diffusion
as a byproduct in manufacturing cellulose while new high efficiency gasification systems are used
to convert A. donax into different energy sources e.g. ethanol and bio-diesel. The canes contain
silica, perhaps the reason for their durability, and have been used to make fishing rods and
walking sticks. In musical instruments it is used to manufacture reeds for woodwind instruments
such as the oboe, bassoon, clarinet and saxophone as well as the chanter and drone reeds of many
different forms of bagpipes and in the manufacture of flutes and panpipes.
Identification: Arundo donax is easily
identified - mostly because of its
particularly robust appearance. There are
two colour versions; the variegated cream
and bright green and plain green.
Distinguishing between Spanish reed and
our indigenous common reed (Phragmites
australis) is quite easy Phragmites
australis (common reed/fluitjiesriet) is a
much more delicate plant that grows in a
wet environment and does not have the
large leaf lobes of Spanish Reed. Mature A.
donax plants are very tall - normally about
6 meters but can reach 10 meters. The
leaves are up to 700mm long and 80mm wide with persistent leaf sheaths on the stem, rather like
a massive grass (it is classified as poaceae - the grass family). The inflorescence (flower) is spearshaped and cream or brown. The plant seldom if ever produces seed, reproducing vegetatively by
means of rhizomes.
Invasive Status: Classified as a Category One invasive species (must be removed) Spanish Reed is
very competitive and easily out-competes other vegetation. The plant invades watercourses and
also occurs along roadsides and other sites away from water. Stands of Spanish Reed do not seem
to offer any nesting or feeding habitat for birds or other animals.
Control: As with most reeds control is difficult. Its dense growth and thick root masses make
manual or mechanical removal of the above-ground mass of large clumps a challenge. Rhizome
pieces buried under 1-3 m of soil may re-sprout and the damage to surrounding communities and
disturbance of the soil caused by physical removal may be severe. Follow-up after manual removal
is essential. Spraying large plants with herbicide is not effective. Cut back and allow re-growth to
reach about one meter and spray with a glyphosate herbicide. Regular follow-up is the key to
successful eradication.
Indigenous substitutes: Our indigenous restios are the solution for any garden setting. Typha
capensis (Bulrush), Thamnochortus insignis (Albertinia Dekriet), Elegia capensis (Fonteinriet).
References: “ALIEN WEEDS AND INVASIVE PLANTS”: Lesley Henderson. Copyright © 2001
Agricultural Research Council. Problem Plants of South Africa: Clive Bromilow. Wikipedia.