Though a non-native and invasive species, winter heliotrope is relatively easy to control using cultural methods. Picture: iStock

It's poking its head up all over the country over the last few weeks and if I had an answer for everyone who asked me how to eradicate it easily, I’d be a wealthy man. I’m talking about winter heliotrope or Petasites pyrenaicus to give it its botanical name.

The most important factor regarding this plant is that the flowers which are produced during winter and early spring are a very important source of food for bees during these months. The flowers are always described as vanilla-scented though I don’t get it myself.

It is a non-native and invasive species, hailing from Central, Southern Europe and Africa originally. Like many invasives, such as the problematic Japanese knotweed, the winter heliotrope was planted in many gardens during the 1800s as a good ground cover.

It escaped from these gardens and is now widespread throughout Ireland. Only male plants are found in Ireland and thus it cannot produce seed which means that it can only spread vegetatively, in other words by division or root cuttings. This is what makes it so difficult to control. The roots are rhizomes (underground stems) and these rhizomes have plenty of leaf buds which means that it has plenty of opportunity to sprout new leaves.

Anyone who has had it in their garden and has tried to eradicate it by digging it out once, will know that it is a losing battle for if you leave the smallest amount of root, and its impossible not to, then the plant will regenerate with a vigour as if it has been nicely pruned.

The first cousin of winter heliotrope, Petasites hybridus, also called butterbur or coltsfoot, is native to Ireland and the UK. Though similar, it is easy to distinguish from the winter heliotrope as butterbur makes a far bigger and broader plant, reaching up to 1.5 metres in height with leaves often over 50cm in diameter whereas the winter heliotrope will only reach up to 30cm in height. The flowers too are quite different, the butterbur blooms are pure white and more densely clustered than the winter heliotrope.

The main issue with the invasive plant is that it spreads forever and forms a monoculture, crowding out light to all other plants and bullying everything out of its path. The Irish name Plur na Greine translates as flour of the sun, though it does like to keep that sunlight all to itself.

It is easier to control winter heliotrope than many other invasive species. The penny dropped with me many years ago, when I noticed that you tend not to ever see it as a problem weed on lawns, even if it is flourishing around the perimeters.

Lawns are mowed regularly and this is what made it obvious to me that regular cutting of the plant will weaken it to the point of eradicating it.

Every time you cut it or dig some out, you will weaken the colony. So repeated, strimming or cutting and digging will help.

That’s not always practical or even possible depending on where it is growing but there is no need to go spraying unnecessary and damaging herbicides on the plant as, firstly they won’t work and also because it is relatively easy to control physically.

Cover it with a compostable weed block, soaked newspapers or cardboard and further cover this with an organic material as a mulch such as bark, wood chippings, homemade compost or clean topsoil to a depth of 15cm-20cm and this will also work.

If your garden is large enough, I would be inclined to leave a stand of it growing, provided it is not encroaching where you don’t want it and also in the wild, I would leave alone unless it is becoming too much of a problem. The reason I would leave some growing is because of what I spoke of at the top, it is an extremely important food source for bees when there is little else available.

Petasites contain pyrrolizidine alkaloids and whilst the root extract is sometimes used in medicinal drugs, it should never be eaten as these alkaloids are toxic and are believed to be carcinogenic.

This species is included in the Spring Flowering Plants Project which is a collaboration between the National Biodiversity Data Centre and the Botanical Society of Britain and Ireland. This project aims to collect valuable data to improve our knowledge of the current distribution of some common plants. Other plants on the spring-flowering list are bluebell, common dog violet, cowslip, early dog violet, early-purple orchid, lady’s smock (cuckooflower), lesser celandine, lords and ladies, primrose, toothwort, wild garlic, winter heliotrope, wood anemone, wood sorrel, and three-cornered garlic,

You can report sightings of any of these plants through the National Biodiversity Centre website https://species.biodiversityireland.ie.

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