With its ample supply of food and nesting materials, an expert has warned that a compost heap in the garden is “the ideal spot for rats”, no matter the time of year.

However, gardeners should not let pests deter them from creating a compost heap. 

Not only are they a great way of discarding kitchen and garden matter, but they can be incredibly beneficial once added to the garden. 

Matt Jordan, gardening expert for The Greenhouse People, has shared some “mistakes” gardeners make with their compost heaps that “invite rats into your garden”.

1. Not covering a compost heap

Of course, one of the “easiest ways to prevent rats from creating a nest” in compost heaps is by ensuring that they can’t access it.  

Matt said: “An uncovered compost heap will emit odours that will be especially attractive to rats looking for food.”

The type of covering gardeners will need to use for their compost containers may depend on the weather. 

The expert explained: “If it’s very wet, then a tarp is an ideal protective cover. This will prevent the compost from becoming too soggy. 

“Mesh or wire fencing can also be used to keep out bigger pests while allowing for airflow and moisture.” It’s important to note that the cover should be removed when adding new materials to the heap and when turning the heap, to allow air circulation and prevent odours. 

2. Getting the wrong ratio of greens and browns

Getting the ratio of greens and browns right in a compost heap can be tricky for any gardener, however, paying attention to the layering will help ensure compost is nutrient-rich “without inviting pests into your garden”.

A ratio of four parts “browns” to one part “greens” is typically considered to be “the best option” for a compost heap. 

The greens include nitrogen-rich materials such as grass clippings, food scraps, coffee grounds and tea bags, while browns are high in carbon i.e. dry leaves, paper, branches and pine needles.  

Matt warned: “Adding too many greens, typically food scraps, will draw attention to rats searching for food. 

“Be sure to layer brown materials over the greens to promote faster decomposition and reduce the odour of food, which will attract pests.”

3. Using too much water 

A soggy compost heap may “attract rats” for several reasons. Firstly, too much water can cause the compost to become “anaerobic”, which means there is not enough oxygen in the soil. Matt said: “Anaerobic compost heaps often have a foul smell, which attracts rats.”

Too much water also slows down the decomposition process. This means that food scraps, which attract rats, are likely to sit around in the compost heap for much longer than necessary. 

While there is no exact rule for how much water to add to a compost heap, it’s generally best to feel it out. The compost should be damp to the touch but not soggy. If gardeners squeeze a handful of compost, there should be some water drops but not dripping wet.