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I have recently been carrying out some work to create a garden seating area using 20mm blue slate chippings. During the planning stages of this work I had to consider how slate chippings would perform as a solution, and how I could best to prevent weeds growing through. Here is what I have learned about slate chippings and weeds.
Slate chippings do not stop weeds. Slate chippings can help to reduce weed germination, especially when combined with a weed control membrane, but they will not stop weeds growing completely.
Lets go into some more detail and look at some of the different uses for slate chippings, along with the best installation and maintenance methods to follow that will help keep the number of weeds to a minimum!
What are the Different Uses for Slate Chippings?
Slate chippings are extremely versatile, are available in a selection of different colours and sizes, and can be used in a wide variety of different situations. Personally I have used them as a mulch topping for plant pots, and as a surface for garden paths and seating areas. (see below). They can also be used in plant borders and even as a surface for driveways.
In the UK, slate chippings are primarily available in 20mm or 40mm sizes. If you are considering using them for a pathway or seating area the 20mm chippings are best to use – 40mm will be too large.
What are the Pros and Cons of Slate Chippings?
Slate chippings are becoming more and more popular because of their many advantages. They are:
- Relatively inexpensive
- Easy to lay – they can be installed by anyone competent at DIY
- Long lasting
- Low maintenance
* To people, but not to cats: the 20mm size of chippings that I used for both my seating area and path have been ignored by cats. Previous gravel surfaces I had laid using smaller diameter gravel chippings often became the local cat litter tray!
Now for the disadvantages:
- The chippings may need levelling off periodically
- The finished surface is loose so you may find yourself having to collect up stray chippings every so often
- Because the chippings are loose and the surface not water tight there is an inherent risk of weed growth. This is the main disadvantage I have found.
How Can You Minimise the Chance of Weed Growth in Slate Chippings?
The key to minimising any weed growth is to ensure that the original installation is done correctly and to a high standard.
Prepare the soil
The first job when laying chippings is to to prepare the surface of the soil and ensure it is weed (or grass) free. Once this has been done it is best practice to lay a weed control membrane.
Lay a Weed Control Membrane
Weed control membranes act as barriers between the surface of the soil and the chippings. They are permeable so will allow water to drain through from the chippings to the soil but will significantly restrict (but not necessarily stop) the ability of weeds to grow the other way. They will help restrict any sunlight getting to the soil, again reducing the ability of weeds to grow.
There are different sizes and types of weed control membrane available – either standard weed control membrane or heavy duty membrane specifically designed for driveways, seating areas, paths and the like.
The main disadvantage of a weed control membrane is that if you are using it around areas with planting it will potentially restrict the amount of organic matter and nutrients able to reach the soil.
What is the Best Way to Get Rid of Weeds From Slate Chippings?
Once the installation is complete it will need ongoing maintenance to ensure that it is kept weed free.
Weeds coming through slate chippings can be from two sources – they will either originate directly from the soil below the chippings or membrane (if fitted) or they will have been seeded from above into the chippings themselves (most commonly via the wind).
Once weeds start to appear, there are a few different approaches that you can take to keep on top of them. The secret is not to let weeds get too out of control otherwise they will have chance to root extensively and spread: the size of the problem will just multiply. Frequent maintenance is definitely key!
– Pulling Weeds up Manually
The first, and most labour intensive, option is to pull up the weeds manually. This is the most environmentally friendly method of weed control.
When you have a small number of new weeds, especially if they are seeded above the weed control membrane, if you get to them quickly they will be relatively easy to pull up whole. The best way to do this to grip the weed at the base, shake it lightly and pull it up slowly. Once you have removed the whole weed including the root you can relax in the knowledge that that it won’t be growing back.
– Flame Weeder
Another environmentally friendly way of removing weeds is to use a flame weeder. These use heat to kill weeds and no chemicals or pesticides are involved. If you do use a flame weeder it is important to read and follow the user instructions exactly!
Flame weeders work by subjecting the part of the weed above ground to an intense heat, killing it in the process. The drawback of this method is that it doesn’t reach the root system so you will probably find yourself having to repeat the process multiple times as weeds are likely to keep growing back from the root.
– Boiling Water
Pouring boiling water over weeds is another method commonly used to try and keep them under control. If you do this, you will see the weeds go limp within a few minutes of application. The problem with this method is that the roots are not always fully killed off leading to re growth of the weed again in a few weeks time. So multiple applications may be required.
There are also many risks with this process, the most obvious one being that boiling water can scald! So it can be dangerous and if you do decide to kill weeds this way it is vital to take relevant safety precautions! You should apply the water to weeds in a controlled way to ensure it doesn’t splash. Damage could be caused to nearby planting that inadvertently comes into contact with the boiling water.
Applying a 3:1 salt / water solution to weeds growing through chippings will kill them, but again there is an associated environmental impact. The salt will leech into the ground so if you have any planting in the immediate vicinity it may be at risk. After all, salt is not specifically marketed as a weedkiller.
Instead of using salt, you could try using a specifically developed weedkiller.
If your weeds have become massively out of control or you are unable to remove them manually then weed killer could be an option. There are a number of different weedkillers on the market which have been specifically designed for this purpose, all with different ingredients and formulations. If you do decide to use a weedkiller the most important thing to do is to read and follow the usage and application instructions!
If you have planting in close proximity to your weeds then you may experience damage to planting if it comes into contact with weedkiller. In such circumstances manual weed pulling may be the best option!
Slate chippings will not stop weeds completely and, once laid, it is impossible to keep chippings completely weed free. But by ensuring that the chippings are laid correctly in the first place and by carrying out regular ongoing maintenance you can keep weeds (and the work involved) down to a minimum, leaving you more time to reax and enjoy your garden!