By Tomos Jones

The aim of my PhD is to identify which ornamental plants might become invasive in the future, possibly as a result of climate change. Gardeners have an important role in preventing invasive ornamental plants from escaping gardens, through their choice of plants, adopting good gardening practices and disposing of plants responsibly. This was the message of our gold medal winning #GardenEscapers exhibit at RHS Chelsea Flower Show last year.

The premise of Wild about Weeds – as the author puts it “garden design with rebel plants” – is therefore of great interest to me. The book discusses how weeds can – and should – be embraced in gardens. Indeed, the author goes further and suggests weeds that gardeners should be encouraged to consider as integral elements of a garden. It’s full of example weeds, and beautiful photos giving the reader inspiration on how weeds can look great in their garden.

The attractive cover of Wild about Weeds by Jack Wallington

It’s challenging to distinguish between a ‘weed’ and an ‘invasive’ plant. So, let’s briefly try and understand what a ‘weed’ is. I would personally suggest ‘a plant which (insists) on growing where it is not wanted’, which of course doesn’t fit with embracing weeds as integral to the planting palette of a garden. Wallington defines a weed as “a plant that reproduces seemingly uncontrollably”. Weeds can indeed reproduce uncontrollably, which is why they often appear in undesirable spots, but are weeds invasive?

Despite often being used interchangeably, a ‘weed’ and an ‘invasive plant’ are not the same, yet neither are they mutually exclusive terms. An invasive plant is a non-native species which has a detrimental ecological and/or economic impact. A weed, if we follow the author’s definition, can be native or non-native, and perhaps described as a ‘thug’ (i.e. uncontrollable). Importantly, a ‘weed’ should apply to plants which are problematic for gardeners, within gardens, and not if it has a detrimental impact in the wild.

In his introduction, the author alludes to the issue of invasive species with the example of lupins (Lupinus sp.) in New Zealand, of which he says “in the wild [these are] a problem for native plants and wildlife, but in gardens there is no denying their towering beauty”. I don’t disagree with this; invasive plants can certainly be beautiful. Their beauty is often the reason they were introduced as ornamentals in the first place. However, invasive species are one of the main threats to native biodiversity. In Britain and Ireland, most of our invasive plants originated from our gardens. It is therefore important to consider whether a weed is – or could be – invasive in the wild.

So far, it might seem that I’m reluctant to embrace weeds. I’m not, I agree with the author that – beyond aesthetics – many weeds serve a very useful function in the garden such as filling “a gap where nothing else grows”. Weeds can be sustainable options, thriving without the need for input such as water, and they provide resources for wildlife, e.g. pollinators.

Wallington divides weeds into the good, the bad and the unappreciated. ‘Good’ weeds are those that share the same characteristics as any weed, such as self-seeding profusely, yet they are – for whatever reason – already embraced and encouraged by many gardeners. Examples include the native primrose (Primula vulgaris) and the bluebell (Hyacinthoides non-scripta).

Mexican fleabane thriving on a wall in Jersey (Photo by Alastair Culham).

Also included as a ‘good’ weed is Mexican fleabane (Erigeron karvinskianus). This is undoubtedly a pretty plant; it has an unruly and unkempt habit which makes it look rather ‘natural’ growing in cracks and along walls, as it if belongs. Yet, as the name suggests, it originates from Mexico. It is a species which could become increasingly problematic, perhaps invasive, in the wild. I’ve seen it dominate walls in Jersey, enjoying the slightly warmer climate perhaps.

The book continues with examples of ‘bad’ weeds, plants that (most) gardeners do not want because they are very difficult to get rid-of once they’re in your garden. The ‘bad’ weeds include invasive species (at least here in Britain and Ireland), such as Japanese knotweed (Reynoutria japonica, syn. Fallopia japonica) and Himalayan balsam (Impatiens glandulifera) which he described as “a very pretty weed with beautiful, sweetly scented pink flowers”. The author acknowledges that it is “very invasive in damp soils and especially on the banks of streams…”. Both plants fall under UK legislation in efforts to control them as invasive species.

The rest of the book is dedicated to the ‘unappreciated’ weeds, and I’ll pick one example, the bellflowers (Campanula poscharskyana and C. portenschlagiana). For me, bellflowers exemplify differing attitudes amongst gardeners towards weeds. They grow in my grandparents’ garden, thriving in cracks in walls and paths. For my Taid (grandfather) it is a weed, which should be removed. For my Nain (grandmother) however, it might well be a weed but it’s a beautiful plant that can successfully grow in corners where even the best gardener would fail to succeed in adding colour. For that reason, it’s a weed which stays.

Bellflower ‘escaping the garden’ (Photo by Tomos Jones).

Wallington writes an interesting profile for each ‘unappreciated weed’, including how to bring them into your garden by ‘weed hunting’ or propagating and how to manage them. To many gardeners (myself included) this seems very odd – at least initially – but why not?

The plant profiles also include comments on ‘invasiveness’; within gardens and also occasionally referring to their invasive status in the wild. Here is criticism of the book. The author encourages us to embrace these ‘unappreciated weeds’ and bring them into our gardens. I agree with this in principal, but he doesn’t give sufficient emphasis on the detrimental impact that invasive species can have in the wild. If a weed is a ‘thug’ in the garden, it’s possible for it to behave the same in the wild at the detriment of native biodiversity.

As I’ve said, a weed and an invasive plant are not the same. Yet, some weeds are invasive and shouldn’t be encouraged in gardens. Other weeds are more difficult. One example is the butterfly bush (Buddleja davidii), an ‘unappreciated weed’. It’s undoubtedly beautiful; its purple flower spikes are normally covered in butterflies. However, it’s arguably invasive here, although doesn’t fall under legislation, but it is also an obvious resource for pollinators.

In the introduction, the author says that the book is for gardeners who (among other things) want to be ecologically responsible. My criticism is not necessarily of the inclusion of any particular plant – especially as the invasive status of a plant depends on where in the world the reader is gardening – but on a missed opportunity to emphasise how important gardeners are in preventing invasive ornamental plants from escaping gardens. There needs to be a better discussion among gardeners on invasive species.

And so, what is a weed? Further, why is one plant considered a weed (e.g. herb robert) and others – perhaps forget-me-not (Myosotis sylvatica) – not? Such questions cannot be answered with certainty, the answers are too subjective and thus individualistic. However, the author will undoubtedly inspire many gardeners to look at their weeds differently. Wild about Weeds is an insightful book, and very topical with an increasing interest in ‘naturalistic’ gardening for which weeds should be considered. Let’s embrace weeds, but with care!

Wild about Weeds by Jack Wallington. Laurence King Publishing. £19.99. ISBN 978-1786275301

See also a review in Gardens Illustrated.