Download Article 70 Pinus radiata - Botanical Society of South Africa

Weeds in our Area (Part Seventy)
By Bob and Ena McIntyre – Garden Route Branch
Pinus radiata
Pinus radiata (radiata pine, Monterey Pine) is another of the ‘pine’ species that are problems in
the Southern Cape. This one originates from the south west regions of North America. As with all
other pinus species that have become problem plants in South Africa the radiata pine was
introduced for commercial purposes. “Escapees” from formal plantations found hospitable and
enemy free surrounds in areas of natural indigenous vegetation and soon established themselves.
Pinus radiata was also recommended as a fairly fast growing, large garden subject well-suited to
the Western Cape and the Knysna areas. Interestingly its attraction as garden subject lay in the
shape (see picture and identification below) - the impressive tall rounded shape making it a
striking solitary specimen in a large garden. Most pinus species seed germinate easily when
conditions are favourable. Their invasive status is that of transformer, and they significantly
increase fire risk. Fynbos, forest gaps, grasslands areas - usually on moist mountain slopes, are the
most affected. Due to the commercial value of the timber production all pinus species have been
classified category two. These are allowed in controlled zones such as registered plantations but
our natural areas should be kept free of these plants.
Identification: Radiata pines are coniferous
trees 12 to 25 meters tall occasionally
reaching up to 30 meters with a sharply
conical canopy in plantations but a broad
rounded canopy when grown in open areas.
The dark green leaves (needles), in bundles of
two or usually three needles are very densely
arranged and 60-150 mm long. The bark is
deeply furrowed and the cones are yellowishbrown, woody, 70-140 mm long and
persistent (long-lasting on the plant and do
not drop easily).
Control: P. radiata (radiata pine) like other
pines does not usually coppice and may be
felled or ring-barked without applying a herbicide. Seedlings and young plants may be hand-pulled
when the soil is damp. No herbicide is registered for this species. The laws regulating the use of
herbicides prohibit the use of herbicides registered for a particular plant species on another
species. This means that herbicides registered for Cluster Pine preclude their use on other pine
species regardless of whether they may work. Follow-up is an essential ingredient with all
eradication programs,.
References: “ALIEN WEEDS AND INVASIVE PLANTS”: Lesley Henderson. Copyright © 2001
Agricultural Research Council. Problem Plants of SA by Clive Bromilow. Ornamental Shrubs and
Trees by Una v.d. Spuy, The A-Z of Gardening in SA by W.G. Sheat
Substitutes: Podocarpus spp (Yellowwood), Widdringtonia spp (Cypress family)