It is possible to use herbicide or organic weed killer to kill unwanted plant growth in organic gardens without introducing any dangerous chemicals into your backyard. There are a growing number of people that will look specifically for organic weed killer even if their garden is not 100% organic.
If you are looking for weed killer for a vegetable garden, it is a reasonable assumption that very few people, if any, will want to spray a lot of unknown chemicals onto plants that you are growing for food. Even if you do not have a vegetable garden, organic weed killer will generally be safer for pets. In all cases, if you are using weed killer you must check the labels to understand what is in the ingredients.
The word ‘organic’ has two different meanings.
One is any substance that is carbon based, which includes almost all weed killers.
The other meaning of organic relates to a product that can be used on land that has been certified for organic food production.
This latter meaning is what we generally use when we refer to organic weed killer, but unfortunately there are not as many of these products available. So if you do decide to buy a commercial weed killer, make sure you check that it can be used on organic land.
Herbicide (which just means ‘plant killer’) is available in two types.
There are some types that only kill certain plants. These are referred to as selective herbicides. For example, a generic leaf weed killer will kill dandelion, clover and other similar types of weeds in a lawn without causing any harm to the grass.
The other types of herbicides are referred to as non-selective herbicides, as they kill all plants. It would be very unusual to use these in a garden but they may be useful to clear weeds from areas where you do not want anything to grow at all, such as a gravel area or driveway.
Non-selective chemical weed killers that kill everything can be very dangerous to use in a garden as they can easily be spread into other areas by rain and stop anything from growing in your garden at all.
The main organic alternative however is vinegar, used in around 15% to 20% concentration in water. You can spray this over any unwanted plants during a dry spell and they will more than likely die off. Also, whilst the weeds may grow back, they are unlikely to grow back so strongly in future. As with all sprays of this nature however, repeated spraying will usually prevent any future growth in that area, so avoid any continuous use of this on areas where you may want to grow other plants later.
For many organic gardens, a better solution may be to use a layer of felt or sheets of newspaper under the gravel or decking where you want to stop the weeds growing. If you have a large area that you want to clear before replanting, you may prefer to use a flame gun to burn off the weeds. Normal safety rules apply however and you should only do this when they are wet, so that the fire does not spread or get out of control.
A possible organic selective weed killer is citrus oil or D-limonene. If you paint this on to the leaves of any unwanted plants, it will strip them of their protective waxy surface, which in turn causes them to dehydrate and die. Obviously you will need to be very careful that you do not contaminate any wanted plants with the citrus oil, as it will inevitably kill them too.
There are some people who are against the use of any type of weed killer in an organic garden, and it is definitely true that you can usually control weeds by hand. However, in some cases such as around paths or in large gardens this can become very difficult and in these cases, organic weed killer can provide a good solution.