How To Recognise Common Garden Weeds: Garden Weed Identification Guide
Weeds in Gardens Are a Problem. Here Is How To Recognise Common Garden Weeds. Discover Simple UK Weed ID That Helps You Recognise Common Garden Weeds.
Weed recognition isn’t easy. Especially when the weed has just germinated and all you see is a cotyledon or two. And even when they grow a little bigger it’s not always obvious what they are. But once you understand weeds a little more it becomes much easier to spot the clues that previously eluded you. For example, does your weed have one cotyledon (seed leaves)? If so its a monocot. And if it has two cotyledons then its a dicot. These simple differences are important clues to what the plant will grow into.
Now check on the size of the cotyledons. Are they big or small? To make judging the size easier think about when you germinated vegetable or flower seeds. Lettuce seedlings are small. Celery seedlings are even smaller. Now think about the size of e sunflower seedling. It’s much bigger. So you have comparative sizes to judge the seedling and cotyledons by.
If you find the botanical words confusing check out my gardening dictionary
Now look at the seed stem (hypocotyl). Is it long or short? Is it green or some other colour. For example, the weed commonly called redshank (Polygonum persicaria) has, unsurprisingly, a red stem.
Now look at the shape of the cotyledons. Are they long and thin (what we call lanceolate)? Or are they heart-shaped? Or maybe they are notched, or pointed or .. well there’s a huge range of shapes they could be and each shape is a clue to the weed species.
Next let’s consider the shape, size and colour of the first true leaves? Each answer we find here is a clue to the species we have growing in front of us. And don’t forget to look at the configuration of the true leaves. Are they in pairs or singles? Or maybe the plant in front of you has a whorl of leaves above the cotyledon. If it has its most likely cleavers (an alternative would be cannabis .. but let’s not go there).
Most weed plants germinate at certain times of the year. So if you are seeing a lot of the same weeds germinating in, say, May but not in November, then you have another clue. Later I’m going to describe each weed and give an indication of when you might expect to see them germinating.
More on How to Recognise Common Garden Weeds Below
Are the cotyledons or true leaves hairy? Hairy leaves are another clue to the identity of a seedling or mature plant.
I mentioned coloured hypocotyls earlier. Now look at the rest of the plant for colour. spots on leaves are a real giveaway. But don’t stop there. Look under the leaves as well. They could be a totally different colour underneath.
There is a special colouration I want to finish on. Some plants have a thin waxy layer on their leaves, which makes them look a dullish grey-green or blue-green colour. If you see this you have found a glaucous plant. It’s not the most common colouration so another important clue to help you recognise common garden weeds.
The Tips For Recognising Common Garden Weeds
With all these ID and weed recognition tips you should find garden weed recognition much easier. The basic principals also work in arable situations and there was a time when I could recognise a large number of weed seedlings on farmland or in the garden. Since I’ve stopped being a commercial grower I’ve forgotten many of them.
So as a reminder of look to look for I’m going to list the characteristics and other details of the most common weed plants in the following sections.
What is a Weed?
There is one last question we should ask before trying to recognise our weeds. And that is to ask, What is a weed?
The simplest definition I know is “a plant out of place“.
In other words a plant in the wrong place. And weeds don’t have to be wildflowers or even wild non-flowering plants. When I farmed cereals we sometimes had “volunteer” potatoes grow in the corn crop. They had survived from a previous potato crop and were a real menace in the wheat or barley I grew.
So, in that case, a vegetable became a weed.
And in our veg and flower gardens, we have a much bigger diversity of weeds. Some big, some small, some with beautiful flowers and some with none.
Examples of non-flowering weeds in my own garden are ferns. When I took over the garden 18 months ago we have a bed of mixed strawberries and ferns. The ferns have now gone and the strawberries did better without them. And that’s another topic I’ll cover later in this article on How To Recognise Common Garden Weeds. I’ll be going into some detail on how to get rid of weeds. From smothering them when we start a No-Dig garden or burning them with a flame gun to cultivation techniques and using them as green manure.
Finally, don’t forget the value of weeds. They aren’t all as bad as we might imagine. From the dandelions that give early nectar and honey to those we can eat. Plus some weeds give us a clue as to soil type, soil acidity and a lot more. More on that below.
What Weeds Tell Us About Our Soil
Weeds Are Useful Indicators Of Soil Benefits & Problems. They Give Clues About Soil Acidity (pH), Moisture Content & Drainage, Compaction, Nutrient Levels, Soil Type & More. Read What Weeds Tell Us About Our Soil Now.
I’m not suggesting one weed in isolation will give you answers to all these considerations. But if you look at the range and number of weeds they tell so much. And once you are experienced at doing this its possible to judge a piece of land in seconds. So if you are buying a house or thinking of renting an allotment, it will take you seconds to get an idea of the potential of the land you can see.
Weeds & What They Tell Us about Our Soil
Let’s start with an easy clue that can tell us a lot .. if you know what to look for.
Look at the image. It’s of a weed growing in a field. It might be the field you want to buy or rent to grow flowers. fruit or veg in. What is the weed and what does it tell you about the field?
This is a rush, a species called Juncus. It loves wet places. And if you thought it was a sedge you are wrong, but close enough to identify the fact that this is clearly a wet place.
The difference between rushes and sedges can be remembered if you recall that “sedges have edges and rushes are round”.
The other clue when I took this photo is that the field was very wet underfoot. It’s hard to miss that clue! BUT, in the middle of a drought, when the land wasn’t sodden, the fact there was a rush growing would tell us that the land was usually wet.
Drainage / Moisture Content Indicators; What the Weeds Tell Us
So we now know that sedges and rushes are indicators (bio-indicators) that drainage is poor. Often these are heavy soils. We could probably improve the soil conditions, to an extent, by draining the area with land drains or by “Mole Ploughing” or Mole Drainage. In both cases, the aim is to allow the water to drain away. In lots of cases that is enough to ameliorate the problem for the whole year. But it can be costly and may not be enough in very wet times. For example, the bottom of a valley might be easy to drain in summer and the drier months but have so many springs in the surrounding hills that it’s not possible to control the issue in the winter.
Soil Acidity/Alkalinity (pH) Plant Indicators
Here we have an autumnal image of a sheep on a hillside and the picture is worth a thousand words. It screams information about the soil.
The clue is in the predominance of one particular plant. It’s not the grass!
What is the brown plant? What does it indicate?
It’s bracken. And bracken is an acidity indicator.
Bracken grows on unimproved grassland, moors and commons. Unimproved is a farming term that means normal farming practices haven’t been applied to improve soil conditions and make it more productive. The Romans used lime to counteract “sour” land and lime has been used to counter acid land ever since. If you look around the landscape carefully you can often find evidence of lime kilns. For example, near my home, we have a prominent one in the Lime Kiln car park at Budleigh Salterton.
Alkaline soils also have plants that prefer their unique conditions. For example one of my favourite wildflowers is Scarlet Pimpernel, Anagallis arvensis. Another is Red Campion, Silene
dioica. Both are indicators of alkaline soils.
A word of caution here. Many plants grow on a range of soil types and though they may prefer to grow on, say, alkaline soil, may well tolerate slightly acid conditions. And the reverse may be true. It is the combination of plants that give us the real clues and not just one or two plants or plant species in isolation.
Soil Type and Texture
Vipers Bugloss is an indication of well-drained soils and sometimes slightly alkaline soils. And well-drained soils are sometimes sandy in nature. So Vipers Bugloss is sometimes a bioindicator of sandy soil.
Buttercups are the opposite end of the spectrum. They tend to prefer heavy soils. And as we have seen from the section on drainage heavy soils are often wet as well so buttercups can mean we have both wet and heavy soil.
Soil Compaction: What Weeds Tell Us About Our Soil
Soils can become compacted due to heavy vehicles passing over them or even people walking on them when the weather is wet. Soil compaction can happen over years or in a few days. The plant soil indicators are many. Compacted soils mean that deep-rooted plants struggle to get their roots down. The few very deep-rooted ones that do manage to do well as many of their competitors can’t survive the soils drying out above the compaction layer.
What does survive are shallow-rooted and the more fibrous-rooted plants. Plants such as clover, daisies, and some plantains. They will often shrivel up when it’s dry but soon come back to life once it rains.
Clover is a multiple indicator as it tolerates or loves heavy, acid or alkali, compacted soils. So to truly understand the soil we need to use clover as a bio-indictor in unison with other plant indicators.
Soil Nutrient Profiles Indicated By Weeds
Weeds like all plants have nutrient preferences and needs. And these can be used as bio-indicators. For example, we often see nettles as the first colonisers of a site where there’s been a bonfire. Part of the reason is that they are opportunistic early colonisers. But they are also indicators of high potash levels.
Thistles love fertile soils and although a nuisance, are good indicators of fertile soil. Chickweeds, mallow and fat hen are also fertile soil indicators in my experience.
And weeds can indicate soil nutrient deficiencies. Plantains can indicate phosphorus deficiencies. It’s not that they necessarily prefer low levels of phosphorus, its that they tolerate them whilst other plants don’t. And they fill the void provided by the absence of other plants.
Weeds Versus Plants
In a sense, weeds don’t exist. Though often described as plants in the wrong place I prefer to just think of them as plants! They have so many attributes that focusing on the negative seems to me to trivialise them.
Common UK Garden Weeds
Speedwell (Veronica Species)
The beautiful electric blue flower of speedwells is quite intense. There are three species common to the UK garden. V. filiformis (slender speedwell), V chamaedrys (Germander speedwell) and V. hederifolia (Ivy leafed speedwell). In agriculture the main species is V persica (birdeye or common field speedwell).
They look small and insignificant, to begin with. But don’t be fooled. They can all be problem weeds. The reason is partly due to the fact they grow, flower and seed quickly (though the seed is uncommon as many plants are self-sterile. V persica does however produce seed) and partly due to the fact that they can root from a discarded section of stem, spread by hoe and lawnmower. The real problem they cause is that they stifle veg seedlings due to their mat-like growth that competes with other seedlings.
The fact the plant is a perennial adds to the problems it causes. Surviving all winter it soon dashes into growth in spring and stifles everything else before they have time to establish. And if they do struggle through, they are likely to be damaged when we try to how out the mats of speedwells. Pull out part of the mat of growth and it always seems to bring a few veg seedlings with it.
V.persica is an annual so doesn’t normally survive the winter .. though global warming may change that.
Mulches work well. Digging it in doesn’t. Digging tends to bury it and it springs up again very quickly. I get very little speedwell in my No-Dig garden. Speedwells don’t like the looser nature of compost and can be removed whole if they do venture on to my beds.
In the lawn, the best defence is to attack. Stimulate the grass with nitrogen and it can smother out much of the speedwell problem.
Marestail (Equisetum arvense)
The first thing to know about marestail is that it doesn’t seed. It reproduces by spores, much like ferns and by being a very vigorous plant that will regrow from the rhizome. Often referred to as horsetails, this is a plant family that has been around since Jurassic times and is found over most of the non-tropical northern hemisphere. There are numerous species of equisetum but only two are of consequence in the UK, arvense and fluviatile. The latter being the aquatic version sold for use in ponds etc.
Interestingly it doesn’t photosynthesis through its leaves, it does so through the stem which is green. Another fact worth knowing is that the plant has a waxy coating which means weedkillers such as glyphosate are largely useless in controlling it.
Marestail can be quite invasive in gardens and spreads even faster if rotovated or hoed as the cut rhizome grows into a new plant. Hence control methods such as these often propagate it rather than control it!
The best control method I know is to chop it small with a rotavator (I know this sounds contrary advice) and then sheet down the site with an opaque cover to prevent light penetration. The plants will eventually die in the dark. But you have to keep them covered for long enough.
The reason I suggest rotovating first is that if the rhizome is smaller it has less energy to grow a new plant from. Combining this with the opaque cover speeds the process. Even then, it may take months. And in extreme cases a full season.
Beware reintroduction of marestail from adjoining areas. It will soon creep back if given the chance. And spores can reintroduce it as well.
Common field speedwell, Birdeye speedwell, Veronica persica
I love the little electric blue flowers of the speedwell family. But I don’t enjoy the way they seem to germinate and then immediately set seed.
The truth is they are in a class of plants referred to as ephemerals. Plants that actually do germinate and set seed in weeks, so able to exploit the smallest opportunity to survive another year.
The reality is of course that there’s never just one generation. As one dies of old age, at a few weeks old, another has already started to grow to take its place. So, you’d be excused for thinking they last forever. As one dies a sibling takes its place.
Speedwells are dicotyledonous. They grow to 10-50 cm high at most according to the books, but I rarely see one higher than 3-5 cm as they tend to trail along the surface where they can form large mats as adjacent plants merge together. The flower is small, around 0.5 cm in diameter, blue with a dark stripe and white centre that is said to resemble a bird’s eye. The solitary flowers are borne on long slender hairy stems that emanate from the leaf axils.
The seed leaves are medium to large in size, shaped like a slightly rounded Devon shovel. The true leaves are ovate and coarsely serrated, paired on the lower part of the stem but alternate further up the stem.
The fruit is heart-shaped with two distinct lobes. Each lobe (locule) contains 5-10 seeds.