‘Weeds’ with benefits: gorse in sustainable landscapes
Since moving to Scotland from South Africa roughly three years ago, I have come to learn a lot about common gorse, often known as whin. It has become synonymous with the Scottish landscape to me, and I now expect to see patches of its yellow flowers on hills and next to the roadside.
Whin is a member of the legume plant family, which includes peas and beans, and can flower at any time of the year. It often provides the only spark of colour in an otherwise dreary landscape. I admit to being quite partial to its coconut smell, while the flowers are also favourites of bees, as they are an important nectar source early in the flowering season.
a close-up of a bee enjoying the gorse flowers along the Arbroath Cliffs
Although the wide distribution of common gorse across the British Isles would be suggest it is a weed, it is in fact a native plant species. Adding to its ‘weedy’ reputation might be the fact that mature leaves harden into green, thorn-like, spines.
Common gorse can establish quickly and grows especially well in degraded sites with nutrient-poor acidic soils, where it can then form a dense stand, a feature that contributes toward it being perceived as ‘less than favourable’ among many land managers.
Interestingly, gorse is also a metallophyte, a trait that enables it to grow well in sites with heavy metal contamination, such as mine tailings, the waste materials that are left over after valuable minerals have been separated from the ore. Investigation of gorse growing under these conditions has shown that the plants do not accumulate these heavy metals in their above-ground parts, so they are still safe to be consumed by herbivores.
It is gorse’s ability to grow well in degraded sites and its capacity, like many legumes, for ‘biological nitrogen fixation’ (BNF) in association with specific soil bacteria referred to as ‘rhizobia’ that sparks my scientific interest.
In sites where nitrogen is limiting for gorse growth, but compatible rhizobia are present, these bacteria will form structures on the plant roots called ‘nodules’ within which the rhizobia secure atmospheric nitrogen for their plant partner. Studies have identified gorse-compatible rhizobia as belonging to the same group of rhizobia that modulates soybean.
root nodules on a gorse seedling inoculated with a Bradyrhizobium strain. The nodules are the spherical structures on the base of the shoot at the top of the roots
I am part of a group of Hutton researchers that has investigated the influence that gorse might have on soil resilience, like the ability of soil to ‘bounce-back’ after applying stress, and on crop performance, including barley and spinach grown in glasshouse experiments. Our study has found that the presence of gorse had a positive impact on both crop performance and soil health. The results of this investigation have laid the groundwork for greater study of gorse and its ecosystem benefits. A pilot study focusing on the potential of gorse has been included in the ‘legumeES Project’, jointly funded by the European Commission, Swiss Government, and InnovateUK.
Key objectives of this study will be to determine potential positive and negative effects of gorse on crops, to assess whether gorse hedges lessen the impact of soil compaction and erosion and consider the incorporation of gorse in the form of a liquid macerate or green manure and what effect this might have on soil health.
What else can I tell you about gorse?
Gorse provides a habitat for various birds, mammals, insects and reptiles, thereby increasing the biodiversity of a landscape.
Historically gorse had various uses and was cultivated and managed until falling out of fashion. It was crushed as fodder for cattle and horses during winter, and for heating ovens as it can quickly provide sufficient heat while producing only a small amount of ash.
More recently, there’s been a resurgence of interest in gorse. A study at Aberdeen University’s Rowett Institute has highlighted that gorse, harvested from just marginal lands, could provide enough protein to feed millions of people.
In countries where gorse is indeed a prolific weed, people are trying to find a profitable use for it, such as producing fibreboards and biochar, a form of charcoal that is applied to soil to improve its health and fertility.
We now have evidence that gorse can be good for both crop performance and soil resilience, with great potential for slope stabilisation. As future uses of gorse become better established, or re-established (with a science-evidence base), we can hopefully become reacquainted with the scope of ecosystem benefits that can it provides and rethink gorse’s ‘weedy reputation’ – especially in the Scottish landscape.
Let me finish with the sound of gorse. Like all other legumes, gorse carries its seeds in pods which turn black as they mature, eventually shattering when environmental conditions are appropriate. This process is very similar to that of the closely related legume species, broom, whose pods can be heard shattering on this video:
Written by Chrizelle Krynauw
