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June 2014

This month we again revert to our series on alien invasive plants and more specifically those commercially propagated genuses such as Pines (Pinus spp) and Gums (Eucalyptus spp). Most reasonable people accept that commercial timber plantations are an unavoidable necessity in a country such as ours thathas  no indigenous timbers that can meet our huge timber and paper requirements.

The detrimental effect of these commercial timber plantations on the environment is well known, since they are primarily established in our scarce high rainfall grasslands. These are areas of high flora diversity and are critically important in terms of our scarce water resources. It is therefore important that these timber plantations are well managed to limit the spread of alien vegetation within their boundaries and into adjacent areas. It is also important that ALL landowners become aware of their responsibility to identify and curb the spreadof these invasive species.Lesley Henderson of SANBI’s (SA National Biodiversity Institute) Weed Research Programme lists 3 Pine species as invasive in our summer rainfall area.

These are: Slash Pine (Pinusellioitti), Patula Pine (Pinuspatula) and Chir Pine (Pinusroxburghii). The Slash Pine and Patula Pine are currently widely grown in commercial plantations in our area and the Patula Pine is particularly invasive and often seeds itself in areas surrounding commercial plantations. The Chir Pine is no longer grown commercially in SA but spreads rapidly in areas where it has become established. The Slash Pine is the least invasive of the 3 species.

  • Slash Pine: introduced from the SE United States, has a straight clean stem; furrowed grey bark. It has a lightly branched, light green compact crown; adult needles are stiff and coarse and crowded together at branchlet ends. Female cones are 6-14 cm long at maturity, are slightly asymmetrical and cone shapedand yellowish-brown in colour.

  • Patula Pine:originates from the mountains of east-central Mexico. Its bark is initially reddish-brown and flaky but later greyish and furrowed on the lower bole.The crown is somewhat branchy and spreading withbright green, pendulous foliage. Adult needles occur in bundles of three and are slender and flexible. Female cones occur in clusters of 3-5 on short stalks, are pale brown in colour and lustrous, conic to ovoid in shape and bear minute prickles.

  • Chir Pine:originates from the outer ranges of the Himalayas. The bark is brownish-grey, thick and deeply fissured, providing resistance to fire. It has distinctly ascending branches forming a cone shaped to oval, spreading crown.Female cones are large with prominently raised and reflexed scales. It is an aesthetically attractive pine, freely planted for shade and ornament.

Pines are fortunately easy to control as once they are cut down (as close to ground as possible), they do not re-grow as do many other invasive woody plants. Their seed is however wind dispersed and it is imperative that plants are removed BEFORE they reach seeding age. Hand pulling of plants up to 1m height is usually possible as they are shallow rooted. The Chir Pine is however problematic as it can re-grow and there are no registered herbicides for it. Stumps should be de-barked into the ground

References:

Our Green Heritage: The SA Book of trees (1973)
Mike Martyn (Silvex Nelspruit)

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October 2013

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September 2013

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February 2014

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March 2014

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April 2014

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