Best Weed Killer Buyers Guide

A weed: a plant growing somewhere it isn’t wanted. There’s nothing more frustrating than spending numerous weekends mowing, pruning and trimming, preparing your garden for the summer ahead when you look out the window one morning only to see you’ve been invaded! Who invited those dandelions??!! Where did those blasted buttercups come from??!! Is that seriously Japanese knotweed??!! You need to wipe out those flowering infiltrators and fast – they might look all pretty and flowery but, in reality, they’re the leeches of the plant world – sapping precious nutrients from the soil, hogging sunlight and guzzling water, leaving your prize petunias and radiant roses under serious threat. Those weeds need taking down and fast if you’re to stand a chance of saving your other plants.  It’s time to send those weeds packing…

Best Pick Weed Killer

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You need a weed killer. A weedkiller that will tidy up your garden without destroying your healthy plants or breaking the bank. The herbicide market is flooded with weed killer products that claim to be easy to apply, and that is able to get the job done fast, however, in reality, there’s a lot more to choosing a weed killer than the speed it works at and whether or not you need to sprinkle some granules or point a spray nozzle.  Systemic or contact? Selective or non-selective? Gel or powder? Although it might seem a little overwhelming at first, choosing a weed killer doesn’t need to be stressful. Providing you’re clear on the basic herbicide terminology, and you’ve identified the type of weed(s) you’re trying to combat, you can narrow down your search pretty easily. Read on to find out the different classifications of weed killers; which types work best on which weeds; the options on offer when it comes to application and longevity; and any potential hazards you’ll need to watch out for.  

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Identifying your weeds

You don’t need to tell us – weeds are unsightly, obnoxious and downright stubborn!  However, with proper weed identification, you can plan your attack strategically and invest in a weed killer which is tailored to treating your particular weed problem and kills weeds fast. 

Weeds can be classified by their growing behaviour: annual, biennial or perennial

Type of weed	What you need to know
Annual	Germinates and spreads by seedAverage lifespan of 12 months. Winter types germinate in late summer/early autumn; are dormant during winter, and at their most active during spring. Summer types germinate in spring; are active during summer, and die off when the temperature falls
Biennial	24-month life cycle. year 1: Germinates and forms rosettes. Year 2: Produces flowers and seeds
Perennial	Flower annually. Produce long taproots in addition to seeds. Most difficult weed type to gain control of; requires a strong weed killer.

In addition to their growing behaviour, weeds can also be categorised according to their leaves and roots:

• Broadleaf (Dicot): Larger leaves; grow from taproots or fibrous root systems

• Narrow-leaf (Monocot) or grasses: Long narrow leaves; fibrous roots systems

Once you’ve identified the type of weed(s) you’re faced with, and understand their growing behaviour, you’ve got the information you need to begin shopping for the best weed killer for you and your outdoor area.

Types of weed killer

Weed killers come in different forms: powder, granules, liquid and gel. 

The type is important as it affects both the precision and pace at which you’re able to treat a weed-infested area:

Type	Method of application	Used for
Powder / Granules	Drop spreader	Killing weeds in a lawn or another large area
Liquid	Hand-held weed killing spray bottle with a trigger system	Individual lawn weeds, or controlling flower beds/borders
Gel	Painting by hand	Individual weeds; applied to the leaves

Types of weedkiller 

The main types of weed killer include contact, systemic, selective, non-selective and residual. 

It’s important to understand that most weed-killers will fall into more than one category e.g. systemic non-contact. 

How a weed killer works

Residual	Systemic	Contact
Commonly referred to as ‘soil acting’ or ‘drench’ herbicidesGains access to the weeds internal structure via the roots Generally only used in extreme cases due to the negative effect they have on the soil Once applied, soil is deemed unfit for growing for at least two years Best suited to killing weeds on hard surfaces such as paths or drives	Systemic herbicides travel through the weed’s vascular system down to the roots. Can take between 7-28 days to take effect. Works better when a weed is active Highly effective – cuts off a weed’s food and water supply, killing the weed Common herbicides used in systemic weed killers: dichlorophenoxyacetic acid, dicamba, sethoxydim and imazaquin.	Acts on the green – the stem and leaves of a weed  Is then absorbed by the plant and prevents any further photosynthesis Ideally applied early in the day when the weeds are most active due to photosynthesis  Effectively neutralised and locked into soil so cannot be ingested by the roots of other plants You may have to re-apply contact weedkillers several times, as the weedkiller does not penetrate the plant’s roots Can take up to 14 days to take effect
Systemic Vs Contact Vs Residual Due to their aggression and ability to infiltrate the whole weed, systemic weed killers are the best weedkiller choice when dealing with deep-rooted perennials such as dandelions and dock weeds. Contact weedkillers are better suited to smaller annual weeds but do require generous coverage.  Residual weed killers should only be used on hard surfaces and when the use of systemic and contact weedkillers has proved unsuccessful.

Best Budget Weed Killer

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Selectivity 

Herbicides are also classified according to their selectivity. Some herbicides are designed to control a broad range of weeds, while others are designed to control specific types: 

Selective herbicides	Non-selective herbicides
Selective weed killers are formulated to control specific weeds or weed categories, using chemicals which are toxic to some species but less toxic to others.  Regarded as the ‘Albert Einstein of the weedkiller world’ selective herbicides have the ability to ‘select’ the weeds it kills – normally broadleaf – by being able to distinguish between plants’ vascular systems. Consequently, selective weed killers are often the most popular choice of weed killer for lawns and other large areas of turf.	Also referred to as ‘broad-spectrum’ herbicides and kill practically every plant they come into contact with. Often used on severely overgrown, dense areas.   Should not be applied on windy days as highly likely to contaminate other areas. Normally contains glyphosate and/or diquat and glufosinate Best weedkiller for weeds growing on hard surfaces to minimise contamination of the surrounding area
Selective Vs Non-selective The best weed killer for lawns is selective due to the fact it will target the broadleaf weeds but leave the turf unharmed. Non-selective weed killers are advised for treating large areas, along with drives and patios.

When to apply weed killer

When beginning your search for the best weed prevention, you’ll come across pre-emergent and post-emergence weed killers; you may also come across pre-plant and established stands although these are less common. Knowing the differences between these types of weed killers and how to correctly use them throughout the year will have a significant impact on how effective your weed killer will work during active growing periods. 

When to apply	Additional information
Pre-plant	Applied before planting – typically from several days before up to directly prior to the planting
Pre-emergent weed killers	Applied Jan – April prior to germination  Preventative strategy Commonly used to control perennial grassy and broadleaf weeds have no effect once germination has occurred
Post-emergence weed killers	Applied to saplings – designed to kill words post-germinationMost effective when weed plants are young (prior to them producing their own seeds)
Established stands	Designed for weeds which have an established root system Generally selective

Weedkiller science 

Weedkillers are the assassins of the plant world. You’ll find the chemical formula specific to each brand and type of weed killer clearly displayed on the label. 

The most common weapons of choice…

Action	Effect
Desiccators	Dehydration of plant cells
Acids and bases	Chemical burning of plant cells
Nutritional controls	Change to soil pH resulting in unbalancing of vital nutrients
ACCase inhibitors	Disrupts cell membrane production
ALS inhibitors	Starves plants of vital amino acids
EPSP inhibitors	Disrupts the production of vital proteins
Synthetic auxin	Inhibits plant growth and development

Herbicide Safety Guidelines 

The herbicide(s) used in weed killers varies depending on the brand, type and form of application. Glyphosate is the most commonly used herbicide in the UK. It is deemed safe to use providing manufacturer’s guidelines are followed; it was last reviewed in 2018 when it was granted a new 5-year licence for use in Europe.

Applying weed killer safely

• Avoid areas of exposed skin
• Wear gloves
• Protect your hair and head with a hat
• Wear eye protection – ideally goggles 
• Consider a face mask particularly if you’re treating a large area, or during windy conditions  
• Wash any tools or equipment thoroughly to remove all traces of herbicide for future use
• Clothing worn during application should be soaked before being washed separately to other garments
• Shower thoroughly 

Upon completion of the application, it’s advised to keep animals and young children away from treated areas until well after the application has dried, ideally for 24 hours, or at least overnight. If possible, waiting for a heavy downpour is always useful in terms of neutralising treated areas. 

Identifying common types of UK weeds

In order to be able to choose the best weed killer for the job, you’ll need to identify the weeds you have growing in your garden. Dandelions, buttercups, nettles – we all know what they look like, but what about the ones we don’t recognise?

If we’re honest, we’ve all at some time or another contemplated, “Is that a weed or a flower?”

Familiar UK weeds

Common weed	Description
Dandelion	Common perennial Up to 50cm in height Yellow flowersPost-germination, yellow petals are replaced by pappus – feathery bristles
Buttercup	Yellow flowers; can be spotted white split leaves
Nettles	Green flowersJagged-edged leavesSting upon contact

Not-so-familiar UK weeds

Green alkanet

Hairy-leaved perennial which grows up to 80cm in height with bright blue flower clusters.

Herb bennet

Rosette-forming perennial with rounded leaf tips. Yellow buttercup-like flowers which can reach up to 60cm in height. 

Couch

Blades of grass in clumps. Thin wiry white perennial roots, often banded. 

Bindweed

Twinning perennial climber. White trumpet flowers in summer. Fleshy cream roots run deep.

Japanese knotweed

Tall, bamboo-like perennial with tasselled cream flowers and pink-tinged stems. 

Ground elder

Leaves appear in spring. Lacy flowers in summer. Can grow up to 45cm in height. 

Oxalis

Clover-like, often red-tinged leaves. Small yellow or pink flowers. Fleshy persistent perennial root. 

Lesser celandine

Glossy leaves in spring. Yellow starry flowers which grow up to 5cm. Bulbous roots and perennial bulbs.

Enchanter’s nightshade

Grows to 60cm with opposite leaves. Flower spikes of small white flowers and pink buds. 

Cleavers

Long sprawling annual to 1m with whorls of slim leaves. Insignificant white flowers. Green, hairy seeds produced in large quantities.

Herb Robert

Pink flowers, red-tinged stems and lacy foliage from a central rosette. Strong musty smell. 

Bittercress

Annual rosettes of small rounded leaflets. Small white flower spikes up to 10cm

Creeping thistle

Perennial that spreads out by deep roots and readily seeds. Spiny leaves rise from rosettes. Lilac flowers in summer.

Rosebay willowherb

Ornamental spires topped with purple flowers in summer. Invasive perennial. 

Horsetail

Fir tree-like plants which can grow up to 60cm. 

Annual meadow grass

Clumps of narrow-bladed, low-growing grass often found on paths, lawns and in borders. Short pale white flower spikes.

Docks

Can be tapered or broad-leaved. Flower spikes in summer. Perennial, deep growing, forked taproots. 

Best of the Rest

Last update on 2024-12-12 / Images from Amazon Product Advertising API / As an Amazon Associate I earn from qualifying purchases

Last update on 2024-12-12 / Images from Amazon Product Advertising API / As an Amazon Associate I earn from qualifying purchases

Last update on 2024-12-12 / Images from Amazon Product Advertising API / As an Amazon Associate I earn from qualifying purchases

Frequently Asked Questions