To Plant or Not to Plant Erigeron?

Erigeron karvinskianus Image by pen ash from PixabayErigeron karvinskianus Image by pen ash from PixabayThe absolutely irresistible seaside daisy (Erigeron karvinskianus) is extremely popular, and for good reasons, but did you know that in many regions of the world it is classified as an invasive plant. Read all about it below and decide if you still want to plant it or not?

Erigeron karvinskianus is a small, evergreen perennial plant that belongs to the daisy family, and is native to the upper elevations of tropical America, along the Central American region of the American Cordillera, where it is found on slopes and summits from 900 to 3500 metres high. It grows mostly on steep, open banks or hillsides, often on cliffs or in rock crevices, and is abundant in damp or wet thickets or open forest, often in pine-oak forests at elevations of 900 to 3700m, and most abundantly at elevations of 1300 to 2800m. It is a generalist species that tolerates a broad range of environmental conditions.

It is often confused with its close relative the lovely English daisy (Bellis perennis) and has many common names including: Seaside Daisy, Latin American Fleabane, Santa Barbara Daisy, Spanish Daisy, Karwinsky's Fleabane, and Bony-tip Fleabane.

The seaside daisy is a graceful, trailing, woody-based perennial which is noted for its endless production of small daisies throughout summer, and sporadically throughout the year in frost-free regions. The soft and whimsical looking pure white daisies, with their sunny centres, turn a lovely rosy-pink and lavender as they mature. This ground-hugging groundcover forms a low mound of hairy, grey-green leaves, and the leaves have a red tinge if the plant is grown in poor soil.

Erigeron karvinskianus is freely available throughout South Africa, and remains very popular with gardeners, but I was shocked to learn how invasive it can be. Today it occurs widely as a weed in subtropical and temperate regions of the world. It can grow in almost any open habitat, and reproduces and spreads rapidly to form such dense mats that they often smother native plants. It also produces huge amounts of seeds that travel long distances, because they are adapted for dispersion by wind. And, because there is no information on its natural enemies, it is even harder to control without the use of herbicides.

It is considered as one of the major invasive plants in Hawaii and Réunion, and is considered a High Risk weed by the Pacific Island Ecosystems, at Risk assessment. It is widespread in eastern and southern Africa and it is very invasive in Réunion, the Comoros, western India and the Himalayas, New Zealand, Australia and Hawaii. It is treated as invasive, with laws against its introduction, in several countries, for example Portugal, New Zealand, and New Caledonia. However it is still very easily available in dedicated shops, in the mail-order trade and on the internet.

Erigeron karvinskianus is not listed as an alien invasive plant in South Africa yet, and is freely available. I admit, it’s almost irresistible, but I do believe that we should think twice before we plant anything exotic in our gardens, and do our own research on the plants we already have, as well as those we wish to purchase, before rushing out and just buying whatever looks pretty - the choice is yours.

In the Garden:

The seaside daisy will grow almost anywhere - try it as a groundcover in difficult areas, or as an edging plant in a mixed border. It will even grow in the very shallow soil between pavers.

It looks brilliant spilling with abandon over low walls, creeping down the sides of stone or brick steps, or simply tucked into wall crevices, where it seeds itself and spreads slowly with its rhizomatous roots.

If it is planted into hanging baskets or pots its will cascade down most graciously, forming a solid curtain of flowers and foliage.

An added bonus is it attracts bees, butterflies and other pollinators to the garden.

Sometimes, in very hot regions, it may decide to take when a break in summer if it gets too hot, and you may even think it has died, only for it to suddenly reappear when the weather cools down a bit, and once established in the garden, it can pop up in the most unexpected places.

Cultivation/Propagation:

The seaside daisy grows well throughout South Africa, even in the coldest regions, and is known to tolerate temperatures as low as -12°C. In extremely cold gardens it will go completely dormant in winter, only to spring back to life again in spring. It takes humidity and thrives in coastal gardens, and very hot inland gardens. In hot regions it might go completely dormant in the height of summer, but as soon as the weather cools down a bit, it will come back again.

Each plant can spread over quite a large area, spreading 90 to 150cm, and growing about 30 to 60cm tall. The seaside daisy will grow in full sun or semi-shade, in very hot regions it will perform better where it receives shade at midday, or dappled shade throughout the day, and in cooler regions it will flourish in full sun to light shade.

It thrives in sandy soil but will grow quickly and easily in any well-drained soil, including acidic, chalky or alkaline soils. In very impoverished soils, add some compost to the planting holes to help conserve moisture and to get the roots off to a good start. This trouble free, water wise plant requires only moderate watering during dry summer spells, and little or no fertilisation. In warmer regions where it remains evergreen, water less frequently in winter

To encourage fresh, new growth, cut the stems back to ground level in early spring or autumn, and lift and divide large clumps every second or third year, discarding the woody crowns.

Once this daisy is established in the garden, and if it likes where it is growing it will flourish and you will always have it. You will find it popping up in the strangest of places, and it can become invasive, so keep an eye on it and remove small plants which are growing where they are not wanted. If you wish to propagate it simply lift and divide established plants in spring or summer. Seeds can also be sown in spring or summer.

Pests & Diseases:

If grown correctly, the seaside daisy is virtually pest and disease free.

Warning:

Erigeron has no toxic effects reported, but some people who are allergic to members of the daisy may have a reaction.