Spraying weed killer on your lawn or any where in the garden shouldn’t be taken lightly. The active ingredient in weed killer, usually called glyphosate, is a strong chemical and needs care when being used.
So, in this article I’m explaining which types of weed killer are available for use on lawns. You can also read about when you should or shouldn’t be spraying them and how often.
Before I go into it though, I need to tell you that I ALWAYS recommend removing weeds by hand. And if you don’t have loads of weeds to get rid of, then simply use a herbicide once, then look after your lawn through a proper feeding programme and doing a regular overseed with the right type of grass seed for you.
Now that’s been said, let’s get going.
Which types of weed killer are available for spraying on the lawn
Selective Spray Bottle (spot application)
A single trigger spray bottle is perfect for a simple spot application on broad leaved weeds. It’s usually a single action spray that looks like a standard household spray bottle. It’s also called selective because it will only kill the weeds.
It’s extremely easy to apply and can be used straight from the bottle without mixing it with water. The only negative is that it literally does one spray at a time. So, if you have a large area to cover or lots of weeds, then it might not be the best option for you.
A solution is one that needs to be mixed with water before use. There will be concentration and ratio instructions on the packet. These can usually be applied using a watering can with sprinkle bar or knapsack sprayer.
They are used most often needed where there are a lot of weeds across the whole lawn.
Weed & Feed Liquid
Granular weed and feed should only be used in the growing season (more on this below) because it contains a small amount of nitrogen. That means, while killing off the unwanted grasses you’ll be giving your wanted grasses a boost at the same time. Again, this is a solution, which needs to be mixed with water.
It’s most often used across the whole lawn too.
When to spray weed killer
Technically, you can spray anytime between Spring and Autumn when they are actively growing but remember that most weeds don’t make it up to the surface until mid/late Summer. And spray will not affect any that haven’t yet reached the surface.
However, if you’re happy to do one application in the year, the best time is in late August or early September. Mainly because all those unwanted creepers that are going to germinate will have done so by now. Not only that, the ones that have come up during the growing season haven’t been out for a whole winter yet. So, they aren’t as hardy as those which have survived a cold snap from the year before.
Whenever you choose to use it during the year, any application will have an impact on other jobs you want to do with your lawn.
For example, in terms of using herbicide alongside grass seed or lawn feed, this is where you may need to be cautious. Here’s why.
Be cautious when sowing grass seed before and after spraying weed killer
- Don’t sow new grass seed within 6 weeks of using any form of herbicide.
- What’s more don’t spray a herbicide within 3 months of sowing new grass seed
Using lawn feed at the same time as herbicides
It’s not a problem to use lawn feed at the same time as spraying a herbicide. In fact, as we’ve seen above, some products contain both herbicide and feed supplements that help the grass. That’s because herbicide products don’t usually contain nitrogen. So there’s no risk of nitrogen burn.
How often to apply weed killer
I always recommend minimising your use of herbicides. If you look after your grass with regular feeds, then weeds will find it much more difficult to surface. Then you shouldn’t need to use any herbicides at all.
That said, if you’ve left your garden dormant for a while and you’re now on a mission to remove all the weeds or you feel the need to use it regularly, then use 2 different products. The benefit here is that different products usually contain 2 different active ingredients.
For example a spot spray for individual weeds in spring, then a spot solution for the whole lawn in late Summer/Autumn should give you some great results.
Requirements for spraying weed killer
Moist soil but dry grass
It’s all about balance here. You want the soil to be slightly moist but ideally for the grass to be dry. That’s because the solution needs to sit on the leaf so it can work it’s way into the root zone through the plant’s main stems.
No rain forecast for minimum 8 hours
As mentioned above, the leaf needs to be dry when applying. What’s more, it needs to stay dry for ideally a whole day and certainly no less than 8 hours after applying the treatment.
Calm weather so it doesn’t blow into unwanted areas
When using powerful treatments, you want to avoid them going into other areas of the garden because they can cause great harm to other plants. So it’s best to do your work when the wind levels are low.
Out of everything, frost causes your grass the most stress than any other weather. Meaning you never want to apply anything when there’s frost on the ground. That includes your Winter Feeds
A cool evening if applying it in the Summer
It’s not just frost that can cause stress. Extreme heat also stresses out grass massively. So, if you’re gonna do it in the height of the Summer, then be sure to choose a cooler day and do it in the evening when the soil is more likely to have some moisture in it.
Using Weed Killer in Sprayers
Caution must be taken when using any form of sprayer or watering can with this type of treatment. You should never cross contaminate. Meaning you must always wash your equipment thoroughly, immediately after use.
Where possible, I’d suggest trying to use a different sprayer for herbicides as you would for standard liquid fertiliser. Particularly if you’re doing it frequently. That way, you can be sure to avoid cross contamination with standard NPK liquid fertilisers.