If I had a pound for every wildlife gardening article I have read which recommends making a log pile I would be a wealthy man (I’ve even written a few myself). But if I had to give the pound back for each of those articles that didn’t explain why a log-pile is important to wildlife I would be just as poor as I am now. You might think me an obstinate old wildlife gardener but before I make a log-pile I want to know why I should do it and if I understand the reason I might even do it better.
I feel I should start by describing a log-pile but I am thinking that even the most obstinate of gardeners can probably visualise what a pile of old logs looks like, but I do have a point to make. I know that some people, who like their gardens to be perfectly manicured, are turned off by the thought of a messy old pile of logs. But hold on! If you have ever visited a National Trust wildlife garden you will know how beautiful and sculptural a pile of logs can be so you are not allowed to dismiss the log-pile on aesthetic grounds.
So let’s get down to some log-pile positives.
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How a wildlife log pile helps biodiversity
There are plenty of things that grow on log piles. Mosses, lichens, fungi and moulds all thrive on damp logs and each of these supports a range of small insects, they form a micro-habitat of life. The plants begin to penetrate the logs helping the process of decay which helps wood-boring beetle larvae to create their homes.
This log-pile is positioned adjacent to a wildlife pond to attract and support amphibians
Underneath a log-pile the ground is dark and damp, protected from the heat of the summer sun. Here we might find amphibians such as frogs, toads and newts. The logs offer protection from predators and help them to keep their skins moist in this temperature and humidity-controlled environment. As gardeners we should do everything we can to support amphibians because they tackle some of our pest species such as slugs and snails, although it is also acceptable simply to love amphibians without them having a purpose!
In sunnier spots plenty of insects come to log-piles to bask. Here they can find a sunny spot sheltered from the breeze and this is where they like to warm up before they fly or walk off to hunt. Some of the most obvious insects will be the dragonflies and damselflies, both of which are a delight to watch in our gardens.
This female ichneumon wasp has a very long ovipositor which she pushes into logs to find somewhere to lay her eggs
There are other less well-known insect species to be found on log-piles. Look out for long thin insects with narrow waists, long wings and needle-sharp ovipositors, these are ichneumon wasps. Only the females have the long ovipositors which project from their tail end, they use these to probe into the logs to find a spot to lay an egg. In fact this wasp is a parasitoid, she tries to lay her egg inside the larva of another insect, and when it hatches it will eat the host from inside out! Who would have the thought that a log-pile could be the focus of such sinister goings-on.
More insects can be encouraged to set up home in a log pile by drilling holes into the logs. Where these holes face the sun we might find mason and leaf-cutter bees establishing their nests.
Insects are most in evidence during summer but even during the winter log piles can offer a lifeline to hibernating insects and over-wintering larvae and caterpillars. Butterflies such as the peacock butterfly or red admiral butterfly might settle down to hibernate in a log pile, so too might ladybirds and lacewings, two species which will help us gardeners in our fight against aphids next year. If the log pile has large enough gaps at its base then it might even attract a hedgehog to hibernate.
Plenty of other mammals use log-piles particularly wood mice and bank voles but also shrews which search for insects to eat. It might seem surprising, but birds also visit log piles to find food. We have a wren which is often searching for spiders in one of our log-piles and we have seen both green woodpeckers and great spotted woodpeckers chiselling away at the logs looking for grubs.
How to build your log pile – and where to put it
The composition of a log pile, its construction and its placement in your garden will have an impact on the species which will benefit. So, if you can, make a variety of log piles using different types of logs. Have one in a sunny spot (good for basking insects), one in shade (best for fungi and mosses) and one near a pond (great for amphibians).
Using a variety of different logs will enhance the number of species of fungi and mosses because there are some species which will only grow on certain species of tree for example.
Some species have a preference for how the log-pile is constructed. Logs at the top of taller-log-piles will stay drier and these are most likely to attract nesting mason bees and basking insects. Thicker logs take longer to decay so it is a good idea to have various different thicknesses. Research has found that stag beetles like a very particular style of log pile.
It seems that stag beetle larvae fare best when the logs are positioned upright with their bases partly dug into the ground. This gives a range of states of decay in the log-pile. You might think this is too much trouble but if you live in an area where stag beetles occur it would be great if you could do this because they are endangered and need our support. They are also very impressive beasts so you will be rewarded with a wonderful opportunity to watch them.
There is also the state of decomposition of the logs to take into consideration. Log-piles often come alive when they have had a few years to decay. The softer the logs the more likely they are to be inhabited by wood-boring insects and the more fungi will grow on them. You don’t really want the whole log-pile to be in one state of decay, it is better to offer opportunities to a wide range of creatures, so I like to add fresh logs to my log-pile every year.
If you are now worried that your garden might begin to look like a log-merchant’s yard, just take it one step at a time. Make a small log-pile and see how you go. Maybe have a chat with your neighbours and get them to make log-piles too, wildlife doesn’t recognise our garden boundaries quite like we do and it is a good idea for us to encourage wildlife to move between gardens.
Time for me to log-off now!