Unless you look very carefully you will not usually see sprayed weeds in my garden.
I could not manage five acres of gardens without using glyphosate. I have explained in my previous posts how I have created diverse and naturalistic plantings of thousands of healthy plants. I have also tried to show how my gardens provide rich habitats for wildlife. I know many of you do not agree with using glyphosate and I respect your view but for me it is an essential part of what I do.
I believe ‘Roundup’ is a most useful tool to create and maintain beautiful gardens and the purpose of this series of posts is to share with fellow gardeners my experience of using glyphosate over the last thirty years. So far I have described the ‘easy bits’ such as clearing an overgrown plot, clearing fence lines, spraying under coarse hedges, spraying pathways and drives and rough-grass edges inaccessible to mowers, spraying between widely spaced shrubs and under trees. All to varying degrees, are selective methods based on the directional action of the spray. Glyphosate does not know the difference between a plant and a weed. It potentially will kill them all!
There is a fine balance in the care needed when using glyphosate. I find to my horror some men just stand there and vaguely direct their spray in the hope that magically the weeds will be killed and the plants will not. Equally perplexing are those gardeners who faff around spraying a square meter in the time I spray a small garden! There is a happy medium!
It takes less than three minutes to spray my ‘acid border’
It is no secret why the horticultural press say little about using glyphosate among plants. Not only is it of no interest to most gardeners, in inexperienced hands it is an unfortunate way to damage and kill plants. Too many things can go wrong! I am sure you have all seen ‘Roundup footprints’ across the lawn. I will go further. I do not want to persuade inexperienced gardeners to spray among delicate plants at all! What I do want to do is to provide guidance for those who choose to spray to do it well.
Two of the main methods to achieve selectivity with glyphosate are the use of directional application and timing. An example of the latter is when bulbs are dormant you can safely spray above them, more about this principle in my next glyphosate post!
|It might be inappropriate to spray now but it would be ideal in winter|
Although counter-intuitive a professional knapsack sprayer with a long lance is the most accurate way to spray. It is important that the sprayer has a trigger to stop/start application and that the pressure can be adjusted by the pump handle to everything between a mere dribble and a full thrust of spray.
I found it completely inappropriate for ‘spot spraying’ the way our students were taught to spray by agricultural engineers who worked to professional specifications. They were taught to spray with almost continuous liquid flow at constant pressure. ( I once mistakenly bought a knapsack fitted with a constant pressure device and immediately threw the device away!). Such methods are appropriate to agricultural situations where large uniform tracts need to be sprayed accurately per unit area. The accuracy I am interested in is to kill the weeds and not the plants!
Tips to achieve accurate directional spraying with a knapsack sprayer (spot spraying)
- Only spray when there is no wind and it is absolutely still. Early in the morning is frequently best.
- Direct your spray down and/or angle it away from your garden plants.
- The nearer the spray nozzle to the weed the greater the accuracy.
- Vary the spray pressure with circumstances. For a few isolated weeds direct the nozzle close to the weed and give little more than a squirt. For larger weedy spaces hold the nozzle a little higher and pump a little harder.
- Do not spray at too high a pressure. I usually achieve sufficient pressure with two to four thrusts on the handle - maintained by a single thrust as the pressure subsides. In truth, I find it difficult to describe what I do, it is so instinctive and varies with circumstances.
- Do not attempt to control pressure with the trigger. It should be either, off or on!
- Although it is wasteful and normally counter productive to spray to ‘run off’ I am quite happy for this to occur when spraying a rosette forming weed like epilobium in winter when ‘stem flow’ will direct it to the roots. Although leaving no horticulturally significant residue in the soil, glyphosate will be absorbed by basal roots for a little while.
- Although it is normally alright for the bark of woody garden plants to be wetted any green plant tissue will absorb weedkiller.
- Do not spray anywhere near soft actively growing plants. Unless you are exceptionally skilled the best weed control in your vegetable garden is with a hoe!
- Normally use the glyphosate at the lowest recommended dilution.
- Practice first. I once had a colleague who found his former employer expected him, on his own, to control weeds in a small park. He taught himself to spray accurately with pure water in his knapsack and carefully sprayed around upturned plant pots on a concrete surface. When he could wet the concrete and not the pots he rightly concluded that he was ready to spray!
- Spray shields over the nozzle are often recommended and some gardeners swear by them. Personally I never use them. I prefer to see what I am doing!
Getting Roundup a bad name
Although to kill established perennial weeds they need to be allowed to make a full head of foliage, this is not the way to tackle ‘weeds from seed’ which should be sprayed when very small. Otherwise you get a mess like the above! The casual observer never sees sprayed weeds in any of my gardens.
Anyone unfamiliar with glyphosate spraying should read all these previous posts before attempting selective spraying.
If you read this post you might doubt my competence to spray.
This links to control of ‘weeds from seed’