How to Mix Lawn Weed Killer with Fertiliser
How to Apply Weed Killer and Granular Fertiliser
Your weed killer works best when the weeds are growing well which means the lawn has been fed, there is moisture in the soil and the weather is warm.
- In spring apply your Lawnsmith granular fertiliser at the desired time usually between March and May.
- Apply your liquid weed killer late May to July
In autumn you should apply your weed killer anytime after the fertiliser has greened the lawn but before it turns cold.
Why do I need to wait?
Two reasons:
- Weed killer works by massively increasing the growth rate of the weed so that it basically burns itself out. You can increase the speed by which this happens by watering and feeding the lawn at least a week before using the weed killer.
- Because liquid weed killer is so strong and effective most products only allow one or two applications a year. If you apply too early in spring before all the weeds are growing well you'll have wasted an application. In addition, you shouldn't be putting lots of weed killer into the ground unnecessarily. This isn't an issue in autumn.
If you can be patient and follow this guidance you'll have such a good result that you'll more than likely eliminate 99% of the weeds and can get away with spot spraying or manually removing the weeds in the following couple of years.
How to Mix Weed Killer with Soluble Fertiliser
When using soluble fertiliser you have the opportunity to mix this with weed killer in the same container and complete two jobs in one! This is best done once the weather warms between late May and late August. This slightly contradicts the advice above regarding waiting but remember, soluble fertiliser reacts very quickly because it is adsorbed through the leaf so no time delay!
How to Calculate the Mix
- The Lawnsmith soluble fertiliser should be applied at 4 to 6 grams per square metre. For this example we'll use 5grams.
- We'll use Weedol as the weed killer which should be applied at 1.5mls per square metre.
- If you're using a watering can with a sprinkle bar you need to use 25 to 50 litres water per 100 square metres of lawn.
- If you're using a sprayer you only need 8 to 12 litres of water to cover the same area as the spray is finer and coats better.
For this example we'll use a lawn area of 150 metres square and we'll use a watering can. This means:
150 x 5 grams soluble fertiliser = 750 grams total
150 x 1.5 mls weed killer = 225mls
It's hard to know how much water to use unless you do a test run with just water. Let's say this test run used 50 litres and my watering can holds 10 litres. This means I need to make up 5 equal lots as follows:
10 litres of water
750 grams fertilizer divided by 5 = 150 grams
225 mls weed killer divided by 5 = 45 mls
Put the water in a bucket, then your soluble fertilizer and weed killer, then give it a good stir until the fertilizer has dissolved. You may end up with a few grains that won't dissolve in the bottom of the bucket so when you pour your mixture into the watering can make sure to leave these dregs in the bucket. This way you won't block the sprinkle bar.
Now go and put it on the lawn and repeat 4 more times.
How to Mix Lawn Weed Killer with Fertiliser
For price comparison this is a 'Super Agro Pro' NOT a 'Super Green'!
More Lawn Food Do's and Don'ts
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Follow a few simple rules to apply your lawn fertiliser and get the best results from your grass whether it's a spring, summer or an autumn feed
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For convenience you can fertilise the seeded lawn area on the day of sowing however, due to changing weather patterns this may not always be best.
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Lawn Food Do's and Don'ts
You can save time and money and get a better result if you use the correct fertiliser for your lawn. Adjust for these and your grass is 90% of the way there.
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The soil in your lawn controls the amount of fertiliser, air and water to the grass roots, therefore sandy and poor soils should be fed more than clay soils
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Lawn Food Do's and Don'ts
Knowing what to use to feed your grass in spring can make a big difference to your lawn whilst saving you time and money.
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Lawn Food Do's and Don'ts
In summer you can use a granular or liquid fertiliser. However, the conditions for application are very important during the warmer and dryer summer months.
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Lawn Food Do's and Don'ts
Autumn fertiliser needs to be able to support the grass nutritionally, give maximum colour to make use of lower autumn light levels and promote deeper roots.
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Lawn Food Do's and Don'ts
There is plenty of root growth in winter as the lawn soil at root depth is invariably warmer than the air. Keeping the roots fed means a healthy resilient lawn.
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Lawn Food Do's and Don'ts
Clay soil tends to be heavy and dense, with poor drainage and good nutrient retention. Your lawn feed should take this into consideration.
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Lawn Food Do's and Don'ts
Sandy soil tends to drain quickly and lacks essential nutrients, so the best lawn fertilizer should provide a generous level of prime nutrients to compensate.
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Seaweed promotes health, goodness and biological activity within the grass and the soil producing a greener, stronger and more disease resistant lawn.
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Lawn Food Do's and Don'ts
Using a proven mix of nutrients you can rapidly enhance the green in your lawn in less than a day. Ideal for application between seasonal feeds or as a standalone fast green-up before an event.
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Lawn Food Do's and Don'ts
Liquid feeding of the lawn is suitable from late spring to early autumn during the main growth period in warmer weather.
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Lawn Food Do's and Don'ts
When spreading fertiliser on the lawn you need to do two simple things otherwise you'll damage the grass: spread the correct amount and put it on evenly.
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Lawn Food Do's and Don'ts
There is only one way to spread fertiliser on your grass safely and evenly and that is with a rotary or broadcast spreader; not by hand or with a drop spreader
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Lawn Food Do's and Don'ts
Watering-in a fertiliser treatment is necessary for fine powdery products such as weed and feed so try using a fertiliser that doesn’t need watering in!
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Lawn Food Do's and Don'ts
There are three factors that control how long fertiliser takes to work. The availability of moisture, the temperature and the type of fertiliser.
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Lawn Food Do's and Don'ts
Lawn fertiliser may not completely dissolve in to the grass for a variety of reasons. Most of them are good and better for a healthy lawn!
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Lawn Food Do's and Don'ts
Use a granular or pelleted feed without weed killer or iron that is slow-release. These settle deep into the grass pretty much out of reach of dogs and cats.
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Lawn Food Do's and Don'ts
Aftercut is very similar to ‘weed and feed’. There are those with weed killer and those without. Do not use the one with weed killer on a regular basis.
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Lawn Food Do's and Don'ts
'Weed and feed' is a clever lawn care idea. The problem is, for most people it doesn't work leaving stripes, burnt grass and even bigger weeds
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Lawn Food Do's and Don'ts
The shelf life of fertilizers can vary widely based on type of fertilizer, storage conditions, and packaging. Here's a guideline for common types of fertilisers.