For years now, South African gardeners have been urged to rid their gardens of invasive alien plants. Ironically, many of these plants were recommended to us as ‘fast growers’ by the local nursery when we started our first garden from scratch in Pietermaritzburg many years ago. Times have changed, along with a broader understanding of how some of the more aggressively spreading alien plants can displace our indigenous vegetation. The former tend to grow well because they are not prey to local insects or diseases.
While we can look back with satisfaction at all the indigenous trees we have planted in our present garden over the years, and having got rid of an infestation of Lantana spp. – as attractive as they are – a recent ‘audit’ shows that we still have a way to go. Many of these plants were either inherited with the garden or have arrived uninvited. In this occasional series I will highlight some of the alien visitors we still need to see the back of.
The first is an old ornamental stand-by in gardens all over the country, the hardy Sword Fern (Nephrolepsis exaltata).
Swathes of Sword Ferns have commonly been used to fill empty spaces where ‘nothing else will grow’ and have even been given pride of place in large pots to provide a flush of green on hot verandas. If you look around, many city buildings have Sword Ferns growing in neglected cracks and they feather damp patches in old walls and outbuildings. Sword Ferns have been popular because they are tough and apparently drought-resistant – qualities that have endeared them to even the most lacklustre gardeners.
The Sword Fern is an import from North and Central America, however, and is difficult to get rid of once it takes hold of one’s garden. I can attest that the small patch we inherited has spread vigorously, almost taking over the area where the infestation began and in doing so has crowded out some of the plants that were growing there. Try pulling them out and you are met with stolons and tubers that break off and get left behind to spawn another colony while your back is turned! Apart from the afore-mentioned, Sword Ferns are also spread by the dispersal of their wind-borne spores.