Why and how to halt the Formosa Lily invasion.
by Bronwyn Egan
The indigenous vegetation of paradisiacal Magoebaskloof consists of grassland and forest. Despite the rich variety of food and medicinal plants, it has, from the earliest years of human habitation, been influenced by plants brought in from other areas, often with no thought of consequence. Most of these plants stayed in their new homes in a well-behaved manner, sticking to gardens, roadsides and the odd disturbed patch of vegetation. Some species however, had wanderlust embedded in their genes. These became the alien plant invaders of today.
Decades ago, Lilium formosanum, was imported from Taiwan as an innocent ornamental plant. It is known under various guises as Formosa lily, St Joseph’s lily, Easter lily and Trompetlelie or Sintjosefslelie. The lily has a magnificent, pungent, white, trumpet-shaped flower, with subtle maroon stripes down the tube. It stands erect on a stem of soft linear leaves, which set off the stunning flower to great effect. In Magoebaskloof it flowers from February to mid-April. Over the last ten years, the winding roadsides have nurtured more and more of these elegant invaders. Although there are some entrepreneurs who collect and sell the blooms, thus curbing the lily’s spread, the seeds are insinuating themselves further and further into the few remaining fragments of Woodbush Granite Grassland that are clinging to our mountain slopes.
Interestingly, lilies do not often become problematic invaders in the countries they’ve been imported into. They are quite particular about their pollinators and soil preference. Lilium formosanum, however, struck it lucky. Agrius convolvulus, a hawk-moth look-alike, is the lily’s pollinator of choice. Being a common and cosmopolitan creature, it has been ready and waiting in South Africa even before the lilies ever stepped off the ship. If we continue to allow the lilies to prosper, they will destroy the fields of Agapanthus near Bramasole that turn purple every high summer, the clumps of perfect-white arum lilies flowering alongside Magoebaskloof’s streams, the hollows of red Hesperantha nodding next to the rivers, Watsonias skirting the mountain slopes, Kniphofias dotting the landscape in yellow and red, Boophane with their fan-like leaves and deep pink flower wheels, and Merwilla squills wreathing our rocks in blue and white. This kaleidoscope of seasonal magic could all be lost in a few years to a Taiwanese takeover! The alien lilies will smother the amazing variety of indigenous living organisms necessary for our mountain ecosystem to provide us with the very air that we breathe and the water we drink. Therefore, L. formosanum has been classified in South Africa as an invader plant species falling into category 1b in the NEMBA legislation. This means that it is illegal to propagate, plant or trade in the plant and that it must be removed and destroyed wherever possible. Property owners face hefty fines and/or even imprisonment for non-compliance.
Sadly, it is not easy to remove the lilies. Merely pulling out the plants leaves treacherous bulbs behind which will sprout malevolently into new lilies. Chopping off the flower heads before they seed at least prevents the plant from reproducing but at the moment the most effective control method is to apply a herbicide to cut-stems (5% Hatchet (active ingredient: Imazapyr) in water). The plant should be in its active growth stage, stems should be cut down low and the herbicide applied immediately, for the treatment to be effective. This method allows transportation of the poison right down into the bulb to prevent regrowth. The flower heads or buds and seed capsules should be cut off and carefully transported in sturdy plastic bags to be incinerated. The seeds ripen even if the capsule is not on the plant, so it is very important to dispose of them correctly.
Amongst the gardening gurus, there is talk of an alternative: Lilium longiflorum, another beautiful white exotic lily that is presently not listed as an alien invader, is punted as the lily to plant in L. formosanum’s place. Unfortunately, however, the lilies are difficult to tell apart and for this reason, Lilium formosanum was, until recently, considered to be merely a variety of L. longiflorum. It is safer at present to treat all look-alike lilies in the same way: Off limits. Rather plant some colourful local bulbs instead or choose from the myriad of indigenous South African plants! These are so valuable that their seeds are being collected and stored in cryogenic vaults for the future. You’ll be delighted by their truly South African rainbow nation colours next year!