Sunday 13 November 2016

Will Roundup damage my plants?

How careful do you need to be when using glyphosate?

There may be blemishes in my Spring garden but none are caused by misdirected glyphosate

The answer to the above question is very careful. If you are one of those people who think you can dangle a sprayer and somehow your weeds will be killed and your plants won’t, you are wrong.
Glyphosate is one of the best herbicides ever invented but it does not know the difference between a plant and a weed!

Although knowledge and caution is required to use glyphosate some people  are excessively careful. It always amuses me when gardeners earnestly tell me how they bravely tangle a convolvulus shoot in a beaker of dilute spray for example! If you have a garden full of this weed that way takes for ever. With skilled use of a hand sprayer you might treat all of the bindweed in a small domestic garden in the time that others treat the weed growing over a single plant.

This canopy of bindweed growing over an old shrub provides its own curtain and can be carefully sprayed with a small hand sprayer

You can take a minute to cut this back to the ground and it will be back in a fortnight.
You can spray it with one in forty dilution of 360-glyphosate in five seconds and it is gone for ever
I confess I have been known to do fiddly things spraying such as to place inverted pots and tubs over a friend's delicate plants when surrounded by a jungle of perennial weed!

My example is a little ‘potty’ but if a treasured delicate plant in the garden is surrounded by a mountain of perennial weed this is worthwhile
My article today looks at the balance between over scrupulous care and confident use
You really need to read all of my glyphosate posts to become expert but today I would like to explore how far you can go.

A word of caution for experts
You may know that if working for clients that you can save them a shed load of money and hugely enhance their garden by using glyphosate. But beware. People who are doubtful about chemicals can be hugely sensitive to even one yellow leaf on a plant. You can kill client’s plants with impunity as a result of gardening  incompetence, ill timed pruning and inappropriate soil cultivation. Plant death as a result of shredding surface roots or chopping dormant plants by excessive digging might be regarded as 'just one of those things'. 
If glyphosate has been used anywhere  in such a  persons’s garden it is sure to be blamed. 
Plants are routinely sick and die for all kind of reasons. I have even seen glyphosate wrongly blamed  for leaf discolouration in places of higher horticultural education!

I can say with confidence this dahlia in a mountain village in Tignes has never seen glyphosate
Some clients are extremely happy to pay you for toiling away repeatedly pulling out couch grass rhizomes. Some gardeners are very happy to take their money.

But accidents do happen!

It is worth getting a good knapsack sprayer
These days I only use hand sprayers when visiting friends
I have used glyphosate for about forty years and must have used a fifteen litre professional sprayer more than five thousand times. Other methods of application such as hand sprayers almost as often. Most of the following have happened to me, not all and not very often.

*Walking on sprayed weed and then walking across a lawn.
*Not spraying a knapsack diaphragm dry of liquid and next using a lawn weed killer. You will only do this once!
*Using a leaky sprayer

In an old post Harry describe my plumbing as ‘bodge extraordinaire’

*Spraying when it is too windy, particularly if the nozzle is held high and the pressure too great
*Attempting to spray at a constant pressure when you should be adjusting your pressure to the changing conditions.
*Using a cheap knapsack sprayer. If you are serious get a proper one at up to £200. Think how much more you spend on your mower!
*You might be aware that is safe to spray over the top of dormant bulbs and dormant herbaceous plants but neglect to observe they are starting to sprout. Some Michaelmas daisies and phlox are very sensitive to consequent short term damage.

Levels of skill
What a gardener attempts using glyphosate in his garden should depend on his plant understanding and level of practice. I have just made up the lists that follows but it might indicate a measure of what skills he needs and what he can trust himself to do.

Spraying paths and open areas devoid of garden plants. Spraying fence lines and around artefacts in weedy areas.
Spraying under trees and large shrubs
Eliminating weed in garden areas that are yet to be planted 
Using garden centre gels

Slightly more experienced

You do not need to be very expert to quickly and safely spray this border

Spraying under hedges, under woody fruit and in shrub borders, especially when garden plants are dormant
Spraying where bulbs and herbaceous perennials are dormant
Spraying weedy patches between successive crops


You will need to recognise weeds  here and might cut a few corners 

Selective spraying that might depend on timing and extreme accuracy

Using glyphosate routinely as a principle method of of weed control in flower and shrub borders
Recognition of circumstances when plants are extremely sensitive to mishap and  knowing when to use alternative methods of weed control
Good weed identification skills
Able to make 'management decisions' whether plants should be regarded as a plant or a weed!
Can maintain focus and care when spraying

The poached egg plant is a self seeding annual. You can ‘spot treat’ a rare individual weed that penetrates the canopy. If you have a real  problem you can get a clean start when it naturally dies in July. If excessive seedlings germinate in August and spread too far regard them as weeds!
Advice for users of knapsack sprayers when spraying between plants
This is a list of the kind of tips covered in my previous posts

   * Normally spray commercial glyphosate diluted at between     1in 50 and 1 in 80.
    * Usually your pressure will be a result of between four  pulls on the handle and as low as one. I have even used gravity flow for a mere trickle. 
  • Your nozzle should usually be pointed down and sometimes as low as an inch from the ground. More usually a few inches although as much as a foot above large densely weedy spaces. 
  • Learn to angle your nozzle away from a plant and direct it at the weed. Sometimes place your boot between the plant and a weed. I personally prefer to use a cone nozzle for spraying amongst plants

  • When spraying in tricky situations or where the weeds are sparse you will be using your trigger like a yo-yo. In other situations you will maintain continuous flow.
  • Realise that soft new growth is very sensitive to misdirected glyphosate. Be particularly careful when garden plants are small and when spraying amongst clumps of herbaceous perennials in Spring and early Summer. Recognise when to not even try. Not between your vegetables. Even shrubs that are relatively tough have sensitive leaves if making a new flush of soft growth.
  • The other side of the coin is that tougher stems of more mature plants or the barky bases of shrubs (not green or sprouting) normally suffer no damage whatsoever from minor inaccuracies in direction.
  • In as much that glyphosate is a very poor choice if you actually want to kill shrubs you have to be a very bad sprayer indeed to do shrubs and trees any harm. There are exceptions. Elderberry leaves are amazingly sensitive and even though you need several goes at killing brambles, garden blackberries and related climbing hybrids are very easily damaged. You will never harm ivy!
  • Although if you want to effectively kill a difficult perennial weed such as  ground elder you let it grow vigorously and then spray it all over this is not the same situation to when a sturdy herbaceous perennial receives just a tiny amount of misdirected spray. A large plant usually has the resources to just 'shrug it off' with no damage at all.
  • When herbaceous plants are completely dormant when they have died down you can spray over them and if difficult weeds growing among them are still green it is an opportunity to tackle them. The same opportunity arises when deciduous shrubs have dropped their leaves. Most evergreens with tough shiny leaves are unlikely to suffer harm when you spray under the canopy. You can be very bold indeed when dormant ground covering conifers such as junipers are entangled with weed.  Even some sturdy evergreen herbaceous plants such as Helleborus orientalis  and Cyclamen hederifolium are surprising resilient.
This would be an excellent time to spray still green and vulnerable couch grass. I never need to!

I have hundreds of self sown hellebors in my gardens. If weedy I point the nozzle down close the ground and they are unharmed

You would have to be really incompetent for your spray to harm this juniper. Note you will never eliminate the couch grass if you just pull it out!

Although misdirected glyphosate will not harm this conifer you might just as well pull this weed out

When I spray this area in Worsbrough cemetery the wild fescue is a plant, not a weed

My most useful posts for anyone contemplating using glyphosate selectively are ‘selectivity by direction’ and ‘selectivity by timing’
More than a dozen glyphosate posts can be found in my theme column
I described how I eliminated bindweed from Steven’s garden in a single morning. It never returned
(scroll to end of this post)


  1. Roundup is so dangerous that it is forbidden in the European Union. Linda@Wetcreek Blog

  2. What have you been reading Linda? Sorry it is a rhetoric question, I have seen all the (mainly) misinformed propaganda.

    1. You are abolutely right! I read nothing! A very reliable source gave me my info about the EU. But I trust the WHO report and found this article I will definitely be reading more about this and pulling weeds whenever possible. Thanks for taking the time to write your blog. Happy GardeningšŸ˜‰Linda@Wetcreek Blog

    2. Thank you for your gracious reply. I would imagine we could argue all day and throw our facts at each other.
      Come to think about it just about everything in this world has adamant opposing opinions and they are never resolved.

  3. I've heard there's new studies about it causing amphibian mutations. Your article covers damage to other plants but not to other life forms.

    1. No Oregon91 I have not attempted to address such issues but I have elsewhere.Read my post why the recent proposed ban to amateurs by the EU was misguided. Typical of propaganda, Linda above suggests it was banned when after very intensive consideration it was not. Such distortions- the opposite of the truth - stick in the public mind
      There is much very low quality research in this world and much of it is carried out by vested interest and not all by big bad pharma. The organic lobby are very cavalier with the truth.
      If laboratory experiments douse amphibians with unrealistic concentrations of glyphosate I am not surprised you get a result.
      The 'good old organic' blunderbuss natural derris insecticides killed fish even in minute concentrations.
      I have thousands of healthy amphibians in my gardens such as frogs.toads and rare crested newts. They all thrive

  4. The evergreen microbiota decussata is harmed by glyphosate. I sprayed some weeds near it and the branches that got sprayed went brown and lost all needles. The main plant was not harmed.

    1. I don't know this genus Robert but when I googled it it reminded me of sprawling junipers that I have sometimes tackled in client's gardens when tangled under the canopy with a mass of perennial grass weeds such as couch. It is impossible to spray without wetting a few conifer leaves and I too have noticed little brown patches that grow out after a few weeks in Summer but no harm to the plant overall.

  5. I use this for spot treatment with glyphosate in the borders and think in a small garden it is very useful.

    1. A handy little weeder Brian. As you say spot treatment in a small garden.

  6. Certainly herbicides should be used with great care. I try to avoid them, but I think there are times when their use is justified. Mainly I have used them to paint stumps of buckthorn and other woody plants I'm trying to remove. I once used GrassBGone to eliminate grass in a border. Despite the name, it seriously damaged many of the non-grass perennials in the bed.

    1. There is no herbicide that will safely take out grasses (other than from known resistant plants) where the herbicide provides its own selection. With glyphosate the selectivity comes from timing and direction. OK in the USA they use Roundup Ready crops but we won't talk about that!
      There ARE selective herbicides that DO take out broad level weeds from grass -eg lawn weedkillers
      The product you name is NOT glyphosate and is the sort of thing that gets herbicides a bad name.

    2. Correction The damned spell checker changed broad leaved weeds to broad level weeds!

  7. I spray thistles over an eight acre site and since finally acquiring a Berthoud rucksack sprayer I find I use les than half the amount of spray, presumably due to the finer droplet size.
    Jo M

  8. I guess it is a lot quicker too. I expect you wonder why you did not get one sooner.
    It should be good for a thousand fills!


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