Weedkillers: choose wisely...

A/N: Still in production. Read at your own risk of sanity.

Weedkillers, or more correctly Herbicides are probably the most used chemicals in the garden. They are also the chemicals most likely to cause damage when used poorly, both to people and plants.

What are weedkillers? - Types of weed - Using weedkiller - Types of weedkiller - Conventional vs Organic - Specific Plants

Weedkillers in stock

What are weedkillers?

Herbicides are products to destroy plants, they may be designed for it like glyphosphate or they may be natural products such as fish oil or pelagonic acid. As herbicides are a type of pesticide then as per the Food and Environment Protection Act 1985 it is actually illegal to use pesticides outside of the manufacturers recommendation (such as wrong dosage) or to use them for purposes not listed on the container. In reality most of these laws are nominal for casual gardeners and recommendations can be very vague. Nonetheless weedkillers used carelessly can be dangerous. It is also illegal to apply herbicides to areas outside your own property, such as rented accommodation or allotments, but again those laws are nominal and not likely prosecuted unless damages occur.

Weedkillers are required to state their active ingredient however the other ingredients in the sprayers are considered 'trade secrets' and do not need to be disclosed. This means there may be other toxic chemicals in it, so even with seemingly innocuous chemicals like pelagonic acid follow the manufacturers instructions.

See: This


Types of weed

There are a number of types of weed and they should be treated differently. If you can then you should find out what weed you have, or at least its growth pattern.

Ephemeral: These weeds often have more than one lifecycle per year, this means slow weedkillers are non-effective and they can propagate massively. For   weeds like this then either use contact herbicides or physical removal.

Annual: Annual weeds produce a single life-cycle in one year, they are often quick to grow and flower but not to the terrifying extent of ephemeral weeds. These often overwinter as seed and come back throughout the next year. As long as they are treated quickly then most of the time they are easy to deal with. These can be dealt with by most weedkillers.

Perennial: Perennial weeds are some of the more important. They are persistent and prone to becoming more and more problematic as time goes on. These are often best treated with a systemic herbicide as they often able to regenerate from the simple damage caused by a contact weedkiller.

Other important qualities of a weed can be important to check when dealing with them, many weeds can regenerate from damaged tissue, often even forming new plants, some are chemical resistant by having waxy leaves and some are even hazards!

Taproots, Rhizomes, Tubers: These can make it hard to kill a plant, with physical damage then it is possible you could actually make the problem much worse! This is especially common with Bindweed. On these weeds you should use a systemic herbicide, there are some special methods of application that can be used to deal with weeds like this, but we cannot legally recommend you use them. see: ##using weedkillers##

Waxy Leaves: This is common with many plants, some such as horsetail are almost completely untouchable whilst others like ivy can be dealt with by cutting the plants back and allowing young growth to come through


Types of weedkiller

There are three methods of action with weedkillers, contact and systemic. Each comes with its own benefit and downsides so it can take some judgment to decide which is most suited to the weeds you are treating.


These weedkillers range from synthetic chemicals such as diquat to simple vinegar or certain types of oil. In most cases these will work quickly, they are physically destructive but they only affect the area they are applied to, notably not the roots.


Found in Weedol2. This is a fast and effective treatment for most leafy plants, it destroys the waxy layer of leaves meaning they dry out and die. This is the most powerful contact weedkiller available to the casual market.

Pelargonic acid:

Found in Weedol Fast. This is a weaker contact killer but it has the advantage of being much safer. Pelagonic acid itself has next to no toxicity for either animals or ponds however the surfactants and other chemicals in Weedol Max might.


This is the traditional organic control, at 5% acetic acid then it is only useful on young weeds, it breaks down quickly in water so it dose not damage soil unless overused. Despite this being an 'organic' control, still be aware if blown into your face it can still cause irritation.




These weedkillers are entirely synthetic, they work by being absorbed into the leaves and disrupting growth inside the plant, often targeting the roots.

This is a much more reliable way to deal with weeds and better for older weeds. The downside is that they only work when the weed is actively growing and they take longer to show an effect.


Found in most systemic weedkillers. This is the most controversial of all weedkillers, it has been linked with super-weeds from over use, However it is a very good weedkiller.

This works by disabling enzymes in the plant, meaning it cannot produce new proteins and therefore new cells. When glyphosphate comes into contact with the soil, it binds to it effectively disabling the chemical and making it safe for planting.

Glyphosate is absorbed through the leaves. The best time to spray is when the plant is starting to bud (as this stresses the plant further) but it is effective whenever the plant is in growth. Some weeds with abnormal root structures will need to be treated differently.


This is found in SBK. which is primarily a tree stump killer. It has poor absorptive ability through leaves so when used as a systemic herbicide should only be used on soft growth, when it is used as a stump killer it should be applied to a fresh cut in the stem/trunk at 50:50 with water (although oil supposedly gives much better results).

Synthetic Hormones:

Found in Lawn weedkillers, this is a weedkiller designed to mimic plant hormones, it disrupts growth by stimulating growth points on plants. With monocots (grasses and such) then there is only one growth point, at the base of the plant. This means that it is completely unaffected (if the grass is mature) whilst broad leafed weeds are distorted and killed.

The downside of this is that it takes a long time depending on the weather and is only useable once a year. Although it will not damage mature growth it should not be used on grass younger than six months and seed should not be sown for 6 weeks after applying. This is very effective on fast growing plants such as bindweed.



This is technically the same as systemic but with a different way of treatment. It is found either as granules or a liquid and is either Glyphosate or Tryclopryr. It is applied to a fresh wound in the stump the tree will, even if dead compartmentalize and produce waterproof cells on the cut area.




Preventative weedkillers (pre-emergance) are designed to destroy seeds before or during germination. This is useful for patios and driveways. Preventative weedkillers are also sometimes used in farming so the plants themselves do not need to be sprayed.

Flufenacet and Metosulam

These chemicals are used to destroy seeds and have a low effect on most plants. They are normally combined with glyphosate and provide protection of about 6 months on gravel and paving.



Using weedkillers

When you use a weedkiller, always check the back for instructions before applying. Those instructions supersede anything stated elsewhere, even by us.


Weedkillers should always be used with care, as with all garden chemicals they are safe to use when used properly. Do not use them on a windy day and do not over-concentrate.

When applying through a watering can, be aware of the rose you use. A fine rose lets you apply more evenly and reduces droplet bounce but also makes it more susceptible to wind movement.

If chemicals hit non-target plants then wash with water, most weedkillers are not instant acting and if sprayed with water quickly very little damage will be done. If plants start showing damage after drift with glyphosate then try misting with a seaweed fertilizer (be careful of leaf scorch))

If chemicals get in your eyes then wash with warm water and follow instructions on the back of the container.

Applied as a spray

Most ready to use weedkillers are very easy to use, just point and spray. In these situations as long as you are careful then gloves and goggles are unnecessary however be aware of wind. Sprays are safe a few hours after drying, but if you have a pet that licks or eats leaves then still be a bit careful.

Sprays are very good applicators as they cover a small area very thoroughly and they are probably the most efficient at killing plants but can be frustrating to use over a large area. The reason they are so potent is that the droplets are small and cover evenly whilst large droplets such as from a watering can are prone to bouncing off much like rain water as plant leaves are designed for that to happen.

Most concentrates can be used either as a spray or as a can.

Applied as a water-can

Despite the same coverage on most packing, most of the time you need to apply more from a watering can than from a spray. This is because the water drops are larger and they have more kinetic energy meaning they are more likely to bounce from the waxy coating of most non-hairy leaves. As they have a much smaller surface area to volume, the surfactant common to most chemicals are less effective.

The advantage to using watering cans comes from the volume they can hold. They are useful for treating large areas, especially if they contain a preventative herbicide to stop seeds germinating. When using watering cans it is important to get the dosage right. The best way to do this would be using plain water and working out how quickly you need to walk to apply it at the right strength. If you over-dose then you risk damaging lawns or having the chemicals flow away to other parts of the garden or even into the water system!

Again, most concentrates can be used either as a spray or as a can.


Conventional vs Organic

Weedkillers in organics is an interesting topic, most treatments like using vinegar are made from organic materials but the entire ideal of organic gardening is to not use products to affect the local ecology. Even organic weedkillers are not part of the organic mindset. In addition most home treatments are theoretically breaking the law when used. Realistically most organic applications use physical damage to destroy the surface of the leaves, and are therefore most useful on small or young weeds, that are easy enough to deal with by hand anyway.

If you want to use organic treatments to avoid using chemicals, then look into pelagonic acid and vinegar. If you want to use organic for environmental or ethical issues then just weeding by hand is much better than using even organic treatments.


Trouble Plants

Certain plants are mentioned to us time and time again, plants like Ivy or Bindweed are more difficult to kill with chemicals whilst some like Lords and Ladies or Knotweed are almost impossible! There are however ways to make dealing with them easier.

Bulbs: Bulbs are not affected properly by glyphosate and these are some of the hardest weeds to eradicate, the only treatments that are effective are physical such as contact sprays and even then the bulb must be removed. Try to avoid damaging the bulb as many of these weeds can regenerate from small fragments or offsets.

Ivy: Ivy is a resilient weed, its leaves thicken and become extremely resistant to chemicals over time, the best way to deal with this is to cut it back hard and then apply weedkiller to the tender new growth. If a stronger dose is required then see the Bindweed treatment.

Bindweed: Bindweed is extremely resilient as it has a root structure called a rhizome. This is a fleshy underground stem that can be used to send up new plants and if damaged will multiply massively. Because bindweed is so vigorous then glyphosate often struggles to deal with it, instead you can use SBK which will take longer but work better or you can use the Bindweed Method of applying weedkiller.

These instructions are not from the back of the chemicals packet so use them at your own risk

Bindweed Method: Plants in water photosynthesize when they are hit by light, this can be observed by putting some leafy stems in a glass jar and putting them on a windowsill. When this is done they take up huge amounts of water and this is the root of the bindweed method. By diluting a concentrated weedkiller into this water then it absorbs a huge quantity, much more than the plant would from a simple spray. This is often enough to cripple bindweed and repeated applications will kill it in short notice.

Knotweed: Japanese knotweed is well known for being horrifically invasive and just as horrifically difficult to kill, it is persistent and even small plants can take 3-4 years to kill for a casual gardener. This plant has an incredible regenerative ability, that was evolved to survive on volcanic waste ground. The underground rhizomes can reach 7m long between plants and go as far as 3m down, this makes digging nearly impossible! The major problem with this plant is it can grow 10cm a day and break through concrete causing property damage!

To deal with Knotweed yourself then you must be persistant,, it will take between 3-5 years for a small-medium plant to be killed by it! A larger plant or one that is part of a network of rhizomes will take longer! By repeatedly spraying glyphosate then the plant will start to wear down, often it can re-grow up to three times in one year! Try treating the canes with a stump killer when the canes reach 3ft as the leaves are highly resistant to chemicals. This can be done numerous times in a year as the canes will regenerate or new ones will grow.

Be aware you can be fined £3000 for letting it spread to a neighbour's garden.

Japanease Knotweed: its stems are square and hollow with many nodes.



Weedkillers we stock

Roundup (systemic)

Roundup contains glyphosate and comes in many forms. It can be applied as a rub on gel or as a spray. It is also available in concentrate.

This is the weedkiller that most people turn to when they have a problem plant. it works quickly and has a good wetting agent letting it penetrates most leaves.

As with all glyphosate bases, it is best used when the weather is warm.

We also stock a touch version of Roundup that can be rubbed on weeds in the middle of a flower bed.

Weedol (systemic)

Weedol rootkill contains glyphosate. It is often sold in sachets that cover a set square meterage. It is typically cheaper than roundup and just as effective on soft weeds, although anything resistant should be treated by roundup.

As with all glyphosate bases, it is best used when the weather is warm.

Weedol 2 (contact)

Weedol 2 contains Diquat which is used to destroy the surface of the leaves and to desiccate the plant. this is the quickest weedkiller available to casual gardeners and is quite useful for quick control in the winter.

Dose not kill the plant's roots

SBK (systemic)

Best used as a stump killer, mix it with water and apply to the stump of a shrub or tree. If you have young leaves you can also spray it on the foliage.

Weedol Lawn (systemic/Hormonal)

Weedol Lawn (formerly Virdone) is used to kill lawn weeds, it is slow to work and should only be applied over the whole lawn once (spot weeding is ok).

It will kill grass younger than 6 months and kill seed put down within 6 weeks of application.


Bayer Path and Patio (Systemic / Preventative)

This is most useful as a concentrate as you need to apply it over a wide area for the preventative use to be worthwhile.

It will prevent seed growth for up to 6 months.