Guest post by Sarah Gerhardt

In part 1 of this series, I explored how the term “weed” is mostly a human value judgment, and how the presence of certain weeds can indicate what is happening in the soil or can even improve the soil. Many of these plants are also important for wildlife.

Still, shifting our perspective and learning to appreciate weeds does not mean that we have to let every plant grow where it happens to appear. If you have ever watched a favourite plant disappear under a carpet of weeds, you will know that seeing the ecological value of a plant does not necessarily make it less frustrating in the garden. 

I spend a lot of my time in a client’s garden “doing the weeding”, but before I get started, I need to find out what my client considers a weed. Responses to plants such as Welsh poppy (Papaver cambricum), green alkanet (Pentaglottis sempervirens) or Michaelmas daisy (Symphyotrichum novi-belgii) can vary dramatically.

Some people appreciate (some of) these plants in their gardens. How much they are appreciated often depends on how many of them there are, how wild the client likes their garden to be, and what else they are growing. Sometimes people can get a little hung up on a particular plant, and quite understandably so. If you find green alkanet spreading all over a bed, leaving little room for the plants you had in mind for certain spots, it is easy to want it taken out everywhere.

However, it is worth remembering that the same green alkanet growing in a wilder corner of the garden may create little competition and instead provide beauty and wildlife value. So is it really a weed in that situation?

Some plants considered weeds are worth appreciating or making use of. Others can simply be managed, while there are situations where removing a plant makes good sense. The aim is to move away from automatically treating every unwanted plant as a problem and towards a more measured approach.

Manage or Remove?

Not every weed needs to be controlled in the garden, but some genuinely do. Before ripping out a plant, or, worse, treating it with herbicides, it is a good idea to ask ourselves:

• What is this plant doing here? For example, it could be a ruderal plant (see part 1) simply covering recently disturbed ground and thereby helping the ground to “heal”.
• Is it causing a genuine problem in this location, or am I simply not used to the look of it?
• Is there something I want to grow here that it is preventing from thriving?
• Could I live with it, manage it, or make use of it?
• If I remove it, what will take its place?

The answers to these questions depend largely on where the plant is growing. We may find that the same plant that is a problem in one part of the garden may be harmless or useful in another. 

A dandelion in a closely maintained lawn may be unwanted because it disrupts the lawn’s appearance and competes for space and light. The same dandelion growing at the edge of a border may cause very little trouble and will provide food for pollinators.

Likewise, nettles in a vegetable bed may be an obvious nuisance and a competitor. At the same time, a patch in a less-used corner does not pose the same issues and provides food for caterpillars and habitat for other wildlife.

Once we start looking at weeds this way, we can move away from strict categories of weeds and plants of value and look at weeds differently depending on where in the garden they show up. We can then decide what, if anything, we want to do about them.

To help us decide what to do, we can broadly distinguish four different responses to weeds: tolerate and appreciate, manage and use, remove, or eradicate. The same plant might fall into different categories depending on where it is growing. Ground elder in a wild corner may be something you tolerate, while the same plant covering your carefully planted border might be something you remove. The question is less “Is this plant a weed?” and more “What is it doing here and how do I want to respond?” 

These responses are not objective classifications of plants. They are my own practical gardening judgments, and which response we choose to a particular plant often depends on the garden and the gardener. After all, this is another value judgment, just like calling a plant a weed in the first place. However, qualifying weeds in order of “desirability” for the gardener can be a helpful reminder that we can take more than one blanket response to the plants we experience as weeds in our garden.

Weeds to Tolerate & Appreciate

Many common weeds provide food or shelter for insects, including those needed to pollinate our fruit and vegetables and those that are natural predators for common garden pests. By supporting wildlife, they help us, too. We can learn to appreciate them for that or at least tolerate some of them.

Dandelion, for example, is one of the earliest food sources for pollinators in spring, while ivy offers late-season nectar. Nettles are an important food plant for the caterpillars of several butterfly species, and the seed heads of thistles and teasels provide food for birds later in the year. 

It is a good idea to leave some of these weeds until after they have flowered and set seed, or simply maintain a less intensively managed corner where they can grow. A few dandelions in a lawn, or a patch of thistles or nettles at the back of a garden all have value.

When we get to know the weeds in our garden and understand what value they offer, we can decide which ones we can appreciate or at least tolerate.

Helpful questions to ask include:

• Which weeds are particularly valuable to pollinators?
• Which provide food for birds or larvae?
• Which offer shelter?
• Can you leave them until flowering or seed set, then remove them?

Weeds to Manage & Use

Some plants may be useful or welcome in moderation, but less so when they begin to spread through the beds where you want to grow other plants. This is where management can be useful. You might cut plants back before they set seed, remove some of them while leaving others, or repeatedly cut a spreading perennial to keep it within a particular area. For example, we could leave dandelions to flower so pollinators can feed on them, but if we are concerned about them spreading, we can take off the flowerheads as soon as they finish. This way, we can find a balance between wildlife support and our own garden management desires.

We can also make use of some of the plants we call weeds and thereby keep them in check. For example, chickweed (Stellaria media) can be added to salads or a pesto. Hairy bittercress (Cardamine hirsuta) has a hot, peppery taste, making it a great substitute for rocket in soups and salads. Ground elder has a similar flavour to parsley and goes well with fish. It can also be added to salads, but personally I recommend moderation here as the flavour is quite strong and can easily dominate.

All parts of dandelion are edible. The flowers are beautiful for decorating any dish and can be made into dandelion wine; the roots can be added to stir-fries, and the leaves added to salad. The leaves are quite bitter, so best to always use the youngest ones.

Stinging nettle leaves are rich in iron and can be used similarly to spinach. They also make a lovely herbal tea. Furthermore, nettles can be used to make liquid fertiliser for the garden. 

If we eat any of our weeds, correct identification is essential, and plants from contaminated areas or places treated with pesticides should be avoided.

Weeds to Remove

Sometimes we may find that we simply cannot tolerate a plant in a certain situation in our garden because of immediate competition or practical reasons. 

A weed growing through a carefully planted border may compete with plants we want to keep and thereby reduce their vigour, while one growing through a path may be a practical nuisance.

This is where straightforward gardening techniques are preferable to reaching immediately for herbicides. Hand weeding, hoeing, mulching, and cutting can all reduce unwanted plants. Annual weeds can often be dealt with by preventing them from setting seed, while persistent perennials may need repeated removal or cutting to weaken them.

Understanding how a plant grows makes a big difference. A plant that spreads mainly by seed can be approached differently from one that spreads through extensive roots or rhizomes. Rather than clearing everything, we can concentrate our efforts where the plant is actually causing problems.

Weeds to Eradicate

Finally, there are situations where complete removal really is justified. 

Some plants can pose serious risks to health, cause significant damage, or create wider ecological problems. Japanese knotweed (Fallopia japonica) and giant hogweed (Heracleum mantegazzianum) are examples where simply deciding to tolerate or manage the plant is not necessarily appropriate. 

The word “eradicate” is deliberately strong here. It should be an exceptional response rather than the automatic meaning of “weed control”. Where complete removal is necessary, it is particularly important to understand the plant involved and use an appropriate method rather than repeatedly disturbing the soil or spreading fragments elsewhere.

Conclusion

When rethinking weeds, we do not need to give up on weed control completely, but it is a good idea to look at a plant closely before automatically deciding that its presence is a problem. Some weeds can be tolerated or even appreciated; others can be managed and sometimes used. Some are best removed, and a small number may need to be eradicated. 

The more we understand about the plants growing in our gardens, the better we can decide what response is appropriate for a particular plant in a particular place. Ideally, we should use the least amount of intervention necessary.

About the author: Sarah Gerhardt is a gardener, linguist and punk musician based in Edinburgh. She was head gardener at the Dean Gardens, Edinburgh for 9 years and runs her own gardening business Gerhardt’s Garden Service. Find out more via her Linktree: https://linktr.ee/gerhardtsgardenservice