Tuesday 19 June 2018

Use of a knapsack sprayer for glyphosate spraying between plants

It's easy and speedy to knapsack spray weeds in the spaces between bold clumps
This is written as an appendix to yesterday's article about weed control in Bolton Percy churchyard garden. It addresses the problem of how one can spray speedily and precisely in delicate plant situations. My methods are not widely reported or well understood. If you have already attended an official sprayer training day course you might want to sit down and cry.

Today I make the assumption that you understand glyphosate spraying and perhaps you have read a good number of my previous  glyphosate posts

I recently promoted this sprayer as a Christmas present for  keen gardeners
Although you can work wonders with a very cheap hand sprayer any serious gardener needs a proper knapsack sprayer. Not an amateur toy but a proper professional product such as a Berthoud or a Cooper Peglar at perhaps £150. This is as nothing to the kind of silly money gardeners spend on mowers and other machinery. 
Such a sprayer will last you forever and is far superior to any alternative. False economy is very unwise.

If a fifteen litre sprayer is too heavy for you you don’t have to completely fill it and I rarely do now!

A professional knapsack has the following advantages
  1. It is sturdy and lasts a long time with little need for maintenance
  2. It has a long flexible lance and reaches the weed very easily with no need for stooping
  3. It is extremely accurate and its pressure is easily adjusted when you pump on the handle
  4. It covers large areas very speedily
  5. One fill will spray a very large area, quite easily 1000 sq. metres and professional product goes a very long way. I usually spray the whole of the Bolton Percy acre in two hours with a single fill at a cost little more than two pounds.

Unlike the usual recommendation I always use a cone nozzle. It is far more accurate when you are constantly adjusting height, direction and pressure.

I have more than my fair share of rare and unusual plants. I use just about every known method of weed control in the book but spraying is my backbone
If your idea of spraying is to hold the lance rigid, walk in straight lines pumping energetically look away now. This is completely inappropriate for spraying amongst existing plantings.
The name of the game is to spray all the weeds, not weed-free  soil and never your plants (well there are exceptions and well established clumps and especially woody plants are much more resistant than you think if their leaves only get a light touch of spray).
I might in the past in my zeal to discourage too much pumping and describing the use of the sprayer as a squirter I might have given the impression that I do not get the advantages of the excellent cover of fine spray. I do you a disservice when I tell you that my spray might diminish to gravity flow. More often, I maintain the pressure of several pumps on the handle. I find it almost impossible to interpret for you what is now instinctive for me.
Suffice to say that my spray head pressure and height is constantly varied to plant and weed distribution as is the angle of the spray nozzle albeit normally down. 

Near plants or under low shrub or hedge canopies my spray head almost touches the ground. More usually the cone nozzle angles away from the plants.

My spray head is in constant motion in all plains although mainly horizontal. With zig zag movement I weave patterns in more open spaces between the plants and over the weeds. In a sense I follow the weeds. Sometimes I hover little longer over 'difficult' weeds. 
If I cutback on myself and some weeds get sprayed twice all the better. I can remember and usually see the wet leaves I have already sprayed.

In really complex situations I quickly go over the site a few days later to find the weeds that I have missed.

With a little practice the job is and easy and is safe to yourself and your plants. 

A beginner should get used to his sprayer using pure water! 

360gm/litre glyphosate comes in various guises. Diluted at 1 in 50  in practice they are all the same.
As I am in France today here it is French style
What about the weather?
Some people think their local climate is too wet or windy to justify the expense of a sprayer. They are usually wrong.

Although my most delicate work will be on a still early morning where there is not a breath of air movement this is not the norm. In my very next post (sorry, Roundup again), I describe successful spraying of an overgrown new allotment in a nine mph wind. I do not recommend any stronger!

Ten days after spraying a friend of a friend's allotment the couch grass was as dead as a dodo - and that patch could be planted up immediately if required
When spraying relatively small weeds as described yesterday you do not need the regulation rainless six hours for success. An hour or so is usually enough. Actually very light rain might even enhance take up.
Don’t start spraying if immediate rain threatens but otherwise carry on. My friend Peter Williams commented yesterday that he hardly ever gets caught out by going ahead.
Where you really need the full six hours  - or better a couple of dry days and dewy nights, is where you are spraying well established perennial weeds such as ground elder or mares tail.
Actually it rained heavily two hours after I sprayed the afore mentioned allotment but my pictures show you the formerly rampant couch grass is totally dead.

A small demonstration in the farm field. Intact plants of couch grass sprayed in January, dead in December
Another circumstances where you might want sprayed leaves to stay un-rained on for longer is in Winter. I describe in this post how in a wet Winter or Autumn, glyphosate spraying of still green weeds is the best selective weed control method of all.

One final word. Because glyphosate is translocated and kills via the root it is not necessary to achieve complete leaf cover if the intact weed is in an awkward place 

Let a proper knapsack sprayer be your unpaid gardening assistant
Link to yesterday's post


  1. It was the weight that put me off....I looked it up and it said something like 20kg? I presumed that was empty, in which case it seemed a lot. I even filled a rucksack with tinned food to see what it was like!!!

    1. Come on Sarah. You identified yourself as a thinker in your last comment.
      I looked it up - its 2.2kg - not really heavy. Half fill it and stand in on steps to put it on and it is a cinch
      PS If we go walking I always get the rucksack.

  2. I must have thought too hard, it brought on one of my funny turns. Not 20kg but 5- 6kg according to the brochure. No idea why I had 20kg in my silly head, it might have been my estimate for a full 15L. But with 5L that would still be around 10kg, which seemed quite a lot to me and my rucksack full of tinned tomatoes.
    Page 21 (and while you are there, it's worth looking closely at tip No.5!!)

    1. My reference definitely said 2.2kg but then there are different models. I think the gross reference of 6kg must be a full one?
      I could walk around all day with a gallon of water on my back (5litres) without noticing!
      As to your tips! No. 5 is mere meaningless platitude and as to temperature here in France yesterday I sprayed Peter's ten foot bamboo he wants rid of and it was 25 centigrade. Mind you it was only a five minute job
      The temperature advice is good if you are spraying volatile chemicals especially in a greenhouse!
      Tip no 4 is even worse and is based on the technology of old herbicides where it is only partially significant in limited cases.. Not for roundup - what idiot is going to wait to Autumn to spray?
      I love your little challenges Sarah, keep them coming

    2. 'To avoid chemical waste, do not overpray'
      I'm sure there must be a connection with the hostas there, if I could just work it out.

    3. got it! easily overlooked
      from your earlier hosta comment you won't be creating chemical waste!


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