"Pernicious weeds". Could they be allies?

Some of our native plants are labelled as pernicious - meaning to cause "insidious harm or ruin"; to be "wicked", "noxious", or "destructive" and the status quo is that they must be eradicated.

Is it really the case that plants can be intent on causing such harm? Or have we unfairly villified them? Perhaps there's another side to this story.

There are five main British pernicious weeds: Creeping thistle and its cousin, Spear thistle, both common on sheep-grazed pasture; Broad-leaved dock, and its smaller sibling curled dock, common on arable farms; And last but not least, Common ragwort, commonly found in hay meadows.

Why do these plants plague us? It is actually no accident that they grow where they do. In fact, if we are prepared to look and listen without immediate judgement, we find that they are telling us important information about the land. Not only that, but they are attempting to help in other ways too. Stay with me and I'll let you know some of their secrets.

Lets start with the thistles - found abundantly on sheep farms, in particular fields that have been heavily grazed for many years. Creeping thistle is hated by many, not only for those painful prickles that seem to pierce right through even the thickest of trousers, but for the way the plant spreads underground using its root system. It is a regular candidate for "spraying" when it gets out of control and sometimes even the faintest appearance of creeping thistle can put a land manager into a frenzy. Yet despite attempts at eradication, these thistles keep popping up. Why? Well, if we don't like the prickles, sheep don't like them either! If given the choice, sheep will stay away from areas that are heavily plagued, allowing some of the other grassland species to grow in the relative safety of the thistles. These areas can begin to regenerate - grassland oases in a sea of millimetre-long sward. The thistles are telling us that we may be trying to graze too many sheep on the grassland. At the same time, these thistles are attempting to help the grassland grow back by protecting it. One final important quality of the thistle is that insects, including the beloved bumblebee, love to forage on their flowers! Thistles are often an important nectar source in the heavily grazed landscape.

Next are the docks. These are found on crop fields, most often, but they veer off into pasture and meadows too. Docks have deep roots and large leaves, which gives clues as to their qualities. The long roots of docks push straight downwards through compacted soils that other plants struggle to get a hold on. This action can be the first step in helping break up soil over time, allowing moisture and other plants in and making space for creatures such as worms. The more docks that are found growing in an area, the more compacted the soil is likely to be. The large leaves of docks cover over areas of bare soil, protecting it from the elements. Soil likes to be covered, not exposed, as bare soil gets easily damaged, compacted and washed away, whereas covered soil is protected. Soil is filled with life, and living organisms, whatever their size, need places to take refuge from the sun, the rain and the wind. When the large dock leaves die, they leave a layer of organic matter on the surface, helping protect the soil. If your soil is covered with docks, it is not only telling you that the soil may be compacted, but could also be being left bare for too long a period. You might want to consider making sure that it is covered for more of the year - ideally all year round! You will probably also need to add organic matter. A final word on docks - they produce hundreds of small flowers that are great for small insects, and hundreds of small seeds, that are important for birds during the winter. The leaves are also food for small animals, including slugs and snails, and help keep them off the veggies!

Ragwort, the final pernicious weed, is hated for its poisonous qualities when fed to horses. It is true that if a large quantity is fed to horses in dried hay, it can poison them, and this should always be avoided. However, when ragwort is in a field where horses, or other animals, are grazing, they will not eat it - they know it is not good for them. That is, as long as it is left to flower and is not cut, as the flowers are visible whereas the leaves are not. As with thistles, the presence of ragwort creates areas in heavily grazed fields where the animals will avoid, if possible, allowing regeneration of the grassland in those places. Ragwort also grows in nutritious soils, and is a sign that the soil nutrients are high - usually from the dung of grazing animals. The main useful quality of ragwort is its bright yellow flowers, that are especially attractive to insects and will always be covered with pollinators, so whenever possible, they should be left alone.

All of these plants will disappear naturally over time when land management changes. This may take three or more years - it could be less in the case of thistles, when reducing or removing grazing quickly has an impact - or more in the case of docks, where compacted soil is slow to de-compact and bare soil is slow to regenerate. With docks, the process can be sped up by aerating the soil and bringing in a large amount of organic matter (e.g. compost or manure), to help the soil organisms re-establish. Worms, ants and moles all help with aerating the soil, so providing an environment where they can thrive will be of great benefit. Ragwort will disappear if the grassland is left to scrub over, but to my mind, as long as a field where it grows is not used for hay, especially for feeding to horses, it is such a beneficial plant it should be left in place and appreciated for its bright yellow flowers and quality nectar source.

Is it time to appreciate what these plants are doing for us before grabbing the herbicide or the spade? By listening to nature and making a longer-term plan that benefits the soil and wildlife, we ultimately benefit ourselves!