As autumn deepens and dark nights arrive earlier with each passing day, so our thoughts turn to the wildlife that inhabits our gardens. Many of us will have installed bird feeders and perhaps provided sheltered places for a range of other creatures, even for something as tiny as a ladybird.

High on most of our lists, especially those of us with gardens, will be the humble but delightful hedgehog. It is fitting that we consider these prickly-back urchins as we prepare for autumn because research suggests there has been alarming decline in their numbers within the last ten years. Figures suggest a reduction of about a quarter with more alarming figures forecasting that, unless we do something about it, there will be no hedgehogs left in Britain 20 years from now.

So what can we do? It seems that one problem is our passion for gardening. More and more gardens are being kept scrupulously tidy with lawns being paved over, gardens being made to look more like outdoor living rooms with stonework and even structures being erected and in addition to all that, we are keeping our gardens far tidier than hitherto. Hedgehogs do need a pile of garden rubbish in which to hide.

Many of our improvements create difficulties for hedgehogs – they have nowhere to hide or sleep. Another problem is the reduction of pests due to chemical treatments and this obliterates the food that might otherwise be a lifesaver for a hedgehog – they’re pretty effective at dealing with slugs, grubs and even carrion. One snag is that if pests are poisoned and then eaten by hedgehogs, the hedgehogs will accumulate the poison to such an extent that they will eventually die.

Ponds with steep edges all around are another source of danger. Although a hedgehog can swim extremely well, if it gets into such a pond it cannot climb out and will therefore drown. A short wooden plank leading from the water up to the rim will be a wonderful ramp for a hedgehog, especially if it is rough enough for its claws to grip. A length of wire netting nailed to the board will provide useful footholds.

Some modern garden walls are so well built that they are too smooth for a hedgehog to climb – they are very able climbers but they require rough walls or garden fences that provide footholds, and they can easily cope with hedges.

One very severe problem in the coming weeks will be garden bonfires, particularly those associated with Bonfire Night. Unfortunately, hedgehogs have discovered that a pile of discarded garden waste, even comprising nothing but leaves, will provide a snug and cosy place to sleep. And if a hedgehog goes to sleep around this time of year, the chances are that it will be hibernating and should not be roused, especially by a blazing fire. Left alone, it will remain there until it wakes up next year.

However, hedgehogs do not think ahead in the manner of squirrels. They do not store food for the coming winter and instead rely on their body fat to carry them through their hibernation. If there is a patch of warm dry weather in winter or spring, they might emerge from their sleep to catch a snack or two. In winter therefore, you might see a rather dozy hedgehog trundling along the lane as if it had drunk too much cider – it shouldn’t be too difficult to catch and it’s a good idea to place it in a field where it will be safe, especially from motor vehicles.

Normally, hedgehogs remain dormant until April or even as late as May but a warm spring can arouse them and they will set off to seek food. The chances are there will be none. We can help by providing something for them, like muesli, chopped nuts, pieces of apple or banana or even a portion of tinned dog or cat food.

It has often been thought sensible to provide a saucer of bread pieces soaked in milk but some experts feel this meal does far more harm than good. If you feed them in a regular place at a regular time, they will become extremely tame. As a child, I had a tame hedgehog who slept behind the radio (which was then the size of a modern fridge), and he seemed to thrive on household vegetable waste. When he was not asleep among the radio valves, he went outside. His name was William but I cannot remember what happened to him, nor how old I was at the time.

However, it is worth reminding ourselves that hedgehogs are notorious for the fleas they carry, so if your visiting prickly-back urchin became a pet, then it’s sensible to consider dosing your cats and dogs.

Here in Yorkshire we often refer to them as prickly-back urchins, pronounced in the North Riding as otchens which some people mistakenly pronounce as prickly-back hodgsons. I think the word urchin is derived from the French herichon or even the Latin hericius which were old names for the hedgehog. Do care for these prickly pals.

I have received an interesting letter from a Darlington reader whom many will remember as a popular columnist who shared this page. She is Margaret Cave and she comments on the proliferation of buddleia plants on waste or derelict land where willowherb is more generally found.

As she points out, willowherb, often known as fire weed, is renowned for colonising ground that has been laid to waste or even subjected to intense heat such as fires or bombing raids. The tall, graceful and colourful willowherb seem to thrive on old industrial sites and beside railway tracks where other plants fail to gain a hold.

My correspondent has war-time memories of them flourishing on bomb sites and also on a derelict piece of land in Darlington where a warehouse was burned down.

However, she points out that in modern times, the buddleia seems to be taking over from the willowherb. The buddleia is popularly known as the butterfly bush because its lilac-like flower heads are a constant attraction to butterflies, bees and other insects such as hoverflies.

It grows happily in both wild and cultivated places where it is known for its rapid growth and ability to spread across what many believe to be barren ground. It grows in the form of a strong bush and can reach heights of around nine feet (3m). Its elongated, pointed colourful flower-heads may be deep purple, pink or even white in some cultivated varieties. It is very popular in domestic gardens and parks but also grows wild on wasteland, often beside railways and roads.

I think its rapid spread is due to its seeds being distributed by the wind. This means they reach all manner of sites that may not attract other flowers, and those seeds are able to sprout in very poor earth provided the soil is not too heavy. It is generally accepted that willowherbs take a lot of shifting but it seems the buddleia is able to take over from them and even prevent their growth.

The buddleia was introduced to Britain from China towards the end of the 19th century and it is called buddleia after a botanist called Adam Buddle who wrote a booked called Flora in 1708. This was considered a masterpiece but it was never published, although other botanical experts used it as a source of reference. Now we can remember Mr Buddle in the name of aggressive and determined buddleias.