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« Hot off The Press - The NEW Lawn Guide | Main | Why Weed Control should not be ignored »

Getting Weed Free

Weeds_on_path_2There is a lot of confusion concerning which chemical product for which job. This not only applies to Selective Weed Control on lawns but also Total Weed Control on Pathways, Patios, Driveways and Non Crop Areas such as Car parks. Total Weed Killers should never be applied to a lawn area unless you want to kill off the lawn or grass area to start again and then you should use a Non Residual active ingredient.

Weeds and weed grasses destroy the fabric of a building, fence line, pathways and driveways. We see weed killers as a management tool compared to digging them out yourself which is time consuming and really only removing the top growth and not the roots.

I often watch consumers at the chemical section of the garden centre - there is too much confusion out there and a lot of head scratching ahead of the product being taken of the shelf - it annoys me! Let me break some of the myths and help you all out on this subject so you can purchase with confidence and save a few ££ as well, but most of all get the right product for the right job to acheive the results you are after.

'A Weed is a Plant whose Virtues have not yet been discovered' - Emerson

The success of any weed control task is dependant upon correct identification of the weed or problem, correct selection of the chemical active ingredient and then correct timing of application and then correct calibration of the applicator and application process. We have tackled How to Calibrate a Knapsack in earlier posts.

A lot of chemicals are 'cherry picked' by Consumers off the DIY Warehouse or Garden Centre shelves without much thought to what is actually being purchased. Although some of the more expensive products are shunned because of their perceived high value, the physical amount of active ingredient in the product is far greater in the more expensive pack and the unit cost per square metre sprayed will be far less and the application more successfull. Perhaps this is what the Manufacturers actually want to happen so you buy more product, a synical view but probably true.

The key to it all is to read the label which will give you the field of use and target crop, active ingredient such as Glyphosate and then the amount of each active ingredient in the product expressed as grams per litre of solution, so expect to see 360 grams per litre or even 12 grams per litre in Swan Kneck or Ready to Use Packs. This means that the more grams per litre of active in the solution (normally water based) the more effective the treatment will be cost and the more effective over all. There is some comment required on using the weakest formulation to protect the environment and water but you will use more of a product that has fewer grams per litre of active to get the desired results. Read the small print to see what you are actually buying or often the number of square metres the pack will cover will often give some clue to the strength of product within.

There are primarily three modes of action or types of total weed control chemicals for pathways and driveways and patios. Contact, Residual and Non Residual or Translocated.

A Contact Weed Killer is one that will kill any vegetation as soon as it touches some green vegetation and its speed of kill is controlled by the sunlight. The leaves of the weeds and grasses are severely burnt but the roots may still re generate. One such example is Paraquat or Diquat. 'Weedol Max' is based on a new active of Pelargonic Acid, an active ingredient that occurs in nature and is found in minute quantities in many plants. When concentrated and sprayed onto unwanted plants, this active ingredient becomes a unique fast-acting weedkiller. It works by quickly destroying several layers of plant cells, causing them to rupture, leak and die.

A Residual Weed Killer is one that is based around an active ingredient that is applied to cold soils and one that latches onto the soil colloids or particles to form a barrier in the soils upper surface to prevent the initial spring burst of weeds. One such example is Oxadiazon which is one active ingredient found in Scotts Pathclear Ultra. Residual Weed Killers are best applied in the colder months BEFORE the weeds are present on the area you are treating. If you apply a product like Pathclear Ultra too late in the season, you are not getting the benefit from the Oxydiazon or the Residual part of the control product. I would lilke to see more Pathclear Ultra applied in around February when the soil is traditionally colder to get more use out of the Residual active. The majority of Residual active ingredients break down naturally in the osil when the soil warms up later in the year, another reason why applying in June, the Residual active in the box will not work, soil too warm and or dry!

A Non Residual or Translocated Weed Killer active ingredient will be absorbed by the plant and be transported (translocated) around the plants natural system of pipework to kill the roots and leaves and stems. One common example is the well known active Glyphosate or commonly known as Roundup or Tumbleweed. These products comes in other trade names and guises with varying strengths and in ready to use packs and pump action packs. Common to general belief, Glyphosate is used for Aquatic Weed Control and is a very very safe product for the environment to use if the label is followed correctly, like all weed control products. It neutralises as soon as it touches the ground. It will kill grasses quite quickly - say in around 7 - 10 days with the more resistant woody weeds like Nettle and Brambles taking a little longer. Give the product time to do it's stuff before you start pulling or digging the weeds up! Let the vegetation totally go pink then die back and burn off in the sunlight. Glyphosate disrupts the production of Chloroplasts in the plant, the cells responsible for converting sunlight into sugars or plant food and providing the plants green look - no food production, no plant.Glyphosate is the active to apply to a lawn just ahead of renovating it by starting again. Let the grass plants and weeds dye and burn off then start the renovation as there will not be any chemical traces left in the soil after say 14 days. Glyphosate based control products can be applied to fence lines and build lines, to spray around the base of trees (about eight inch diameter) to conserve water uptake for the trees, especially saplings in plantations. It is safe to spray agains bark but it will kill leaves should it get onto these if the canopy is low or it is just too windy to spray. Local Authorities apply Glyphosate based products to the street pavements and along the edges of buildings where they border to leavy a four inch 'mowing strip' which reduces strimming.

Just to confuse you, chemical manufacturers will create a formulation that utilises active ingredients with one or two or three of the above modes of action to get greater control of the weed problem present. The best option is to have an programme of weed control. In the Spring when the soil is cold, on gravel paths and driveways and patios, apply a product that provides some Residual and Non Residual control of weeds and grasses and then plan to spray one or two Non Residual Glyphosate only formulations to the same area in around June and October to gain overall control.

To help you identify where you have sprayed, it is possible to obtain Spray Indicator Dyes , then it is a case of spraying by numbers!

Be careful not to get any overspray onto your lawn or shrubs and apply when the weather is dry and rain not expected for a period of around half a day otherwise you may get some water and chemical run off onto where you were not planning to weed kill. Be mindful that pets can pick up on chemical spray and then walk this onto a lawn - I speak from bitter experience and I know what I am doing!

Read the Label - Use Pesticides Safely


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