Where do insects go in the winter?

The woods are lovely, dark and deep,

But I have promises to keep,

And miles to go before I sleep,

And miles to go before I sleep.

Robert Frost

Snow covered woodlands, Battleby, Perthshire, January 2015. ©Lorne GIll/SNH

When temperatures fall, life can be very hard for our insects. Some species try to escape the cold by seeking shelter in protected places such as holes in the ground, under tree barks or even inside our homes; others, like bumblebees and some moths, generate internal heat by biochemical processes, just like we do. However, these strategies are not enough to protect such small creatures when it gets really cold.

Many insects just leave: some flies and butterflies undertake journeys of several thousand kilometres to spend the winter around the Mediterranean, returning to the UK in spring.

However, most insects cannot escape the cold British winters. For those that stay put, the greatest winter threat is the formation of ice inside their bodies. Ice crystals within their cells expand, destroying body tissues. If you’ve ever left lettuce or apples in the freezer, you will have seen the catastrophic effect of internal ice after they thaw.

To avoid freezing to death, insects have evolved the capability to go into diapause, which is a state of dormancy similar to hibernation. This can happen when they are eggs, pupae, larvae or adults, depending of the species. Diapause involves behavioural, biochemical and metabolic mechanisms, some of them complex and not completely understood.

We may think temperature prompts diapause, but in fact the daily interval during which the insect is exposed to light (known as photoperiod) is the main trigger. Temperature alone is not a very reliable yardstick; a cold spell may induce diapause too early, and a prolonged autumn may delay it. Either way, the wrong timing could be fatal.

When photoperiod reaches a threshold, a genetically programmed series of events kicks in as the organism prepares for diapause. In the case of an adult insect, it begins accumulating fats, proteins and carbohydrates to keep it fed until the end of cold period, and hormones and enzymes induce a thickening of the cuticle (‘skin’) to reduce water loss. The insect then will look for a safe, well-hidden spot.

As the insect enters diapause, oxygen consumption, feeding and movements are reduced. It then produces large amounts of cryoprotectant (cryo = cold) substances such as proteins, sugars and glycerol, which act as antifreeze – similarly to the products we use in our cars. In the same way that vodka in the freezer remains liquid, these compounds don’t freeze.

By lying dormant in tree trunks, under rocks and cosy holes in the ground, and topped up with natural antifreeze chemicals, the insect has a good chance of surviving the winter. These adaptations are far from perfect; overall winter mortality is high, and for many species just a few individuals can cope. In the case of bumblebees and wasps for example, only queens make it through the winter: all other members of their colonies die at the end of the season.

But the resilience of some insects is truly admirable. The flightless Antarctic midge (Belgica antarctica) produces large amounts of antifreeze sugars and loses up to 70% of its body water when conditions deteriorate. It becomes so dehydrated that it can’t freeze. The Arctic woolly bear moth (Gynaephora groenlandica) spends roughly 90% of its life in diapause, and it survives temperatures as low as −70 °C. But by far the champions of cold resistance are the insect-related Tardigrades, known as water bears. These fantastic animals can survive in suspended animation at −20 °C for 30 years. Not bad for a creature of less than 1.5 mm in size.

By Athayde Tonhasca

Hedge haven

You may have noticed a lot of thrushes about this winter, and possibly even a few waxwings. These winter visitors from the continent love eating berries in trees, shrubs and of course hedges.  With its flashes of yellow, white and red the waxwing is one of those birds that you will on occasion see in hawthorn hedges, and of course in spring the hawthorn hedge is a great resource for our pollinators.

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The loss of many farmland hedgerows shortly after the Second World War was disastrous for pollinating insects in our rural landscape. Flowering hedgerows are excellent for food, shelter and nesting sites, as well as providing a safe and convenient corridor for ease of movement. Rural communities lamented the loss of the flowers which were a distinctive and much-loved element of fruit-bearing hedgerows.  Perhaps less visibly obvious was that insects, birds and small mammals were denied a vital food source and home.

Today hedgerows are increasingly valued for their biodiversity benefits and the planting of new hedgerows is encouraged. But just as ‘Rome wasn’t built in a day’ neither is replacing hedgerows an overnight job.


It isn’t just the loss or rural hedgerows that should be of concern.  The loss of hedges in our towns and cities is an issue too.  And given that domestic gardens represent somewhere in the region of 20% of our townscapes there is good reason to fight the corner for hedges over fences.

We can be pretty confident that urban hedgerows (big or small) in domestic gardens contribute positively to the benefit of nature in towns and cities. At their most basic they provide nesting, shelter and travel corridors. When you add in the fact that they help remove particulates from the atmosphere then the case for hedges is increasingly strong.

A mixed hedgerow, with a variety of trees and shrubs, can have value through the entire life-cycle of pollinators. Blackthorn for example flowers early in the year – just in time to provide a vital food source for emerging bumblebee queens, solitary bees and honey bees. Farms with hedgerows help pollinators and enjoy many other benefits.

A hoverfly feeding on hawthorn blossom. ©Lorne Gill/SNH

Hedges provide shelter for livestock (in both cold and extremely hot weather), , ,  increase the potential for carbon capture and storage in woody biomass, improve water infiltration rates to soil, reduce the potential for flooding and create wildlife corridors across farms. They provide habitat for essential wildlife, including beneficial insects and pollinators. As we increasingly look for Integrated Pest Management solutions pollinating insects provide natural pest control.

We know that pollinators, be they in a rural or an urban setting, need good food sources from early spring to autumn, in order to complete their life-cycles.

Flowering hedges that contain pussy willow, hawthorn and blackthorn are great for those insects on the wing early in the year, whilst come April and May hawthorn and wild cherry can be superb food sources for pollinators. Add to the mix dog rose, guelder rose and hazel and the potential for a hedgerow to be an all-year larder is clear.

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It isn’t just the flowering of hedgerow plants that is important. At the base of hedges in amongst the tussocky grass, or vacated mammal holes, bumblebees might nest.  Bare earth under a hedge (especially if south-facing), might also provide potential nesting sites for solitary mining bees. A range of pollinators from beetles to moths and butterflies will also find those sites useful for overwintering.

In short hedges can be havens for pollinators

hedgerow 1

Managing hedgerows to benefit pollinators

Key to hedgerows being a bonus for pollinating insects is allowing them to flower. Many hedges only really flower on wood that is at least a couple of years old.

As well as planting or managing a range of native flowering shrubs it is important to rotate how often and when hedges are cut. This will reduce costs and be better for wildlife. Many varieties of  tree and shrub species only flower on second year growth, hawthorn and blackthorn, for example, benefit from not being cut every year.

Allowing hedgerows to flower, by moving away from the model of a tidy, short hedge, towards managing one which isn’t flailed annually is one very positive action that farmers can take. Trimming hedges every two or three years instead of annually or rotating areas trimmed increases the flower and fruit crop.  Cutting hedges when in receipt of basic payment scheme support is not permitted between 1 March and  31 August under cross-compliance rules, to prevent damage to nesting birds.

Plugging gaps in hedgerows with native flowering shrubs keeps a wildlife corridor intact and leaving the occasional tree to grow above the rest of the hedge will add diversity.   A recent survey of Scottish native wild apple trees found a number associated with field margins.

Consider cultivating flower-rich strips next to hedges. Flowers such as knapweed, clovers and vetches are great for pollinators.

Aim to cut hedges in rotation, across the farm and aim for an ‘A’ shape, where the densest area is at the base. This will encourage the hedge to thicken up and provide valuable shelter beneath the hedgerow.

By managing a hedge to help pollinating insects you benefit insects, birds and mammals as well as encouraging pollinators onto your farm. Further information on all aspects of hedge management can be found on the Hedgelink website.

Further reading:

The RHS have a guide that talks about hedges in some detail @ https://www.rhs.org.uk/science/pdf/climate-and-sustainability/hedges-for-environmental-benefits.pdf

The RSPB also have an excellent resource which explores the natural shelter that hedges provide and offers advice on selection and maintenance of hedges.

The OPAL website has a lovely article looking at some of the facts and folklore behind hedges.  It also has various excellent resources to help with identification and plant association –






Spoiled for choice

The annual Keep Scotland Beautiful – It’s Your Neighbourhood awards took place recently in Stirling. As part of that gathering, SNH was delighted to support the pollinator-friendly award which this year attracted a stunning range of entrants. 

Recovery Garden Group - wild flowers july

Amongst the entrants were some stand out projects.

Take the Alcohol & Drugs Recovery Garden project in Aberdeen. The group has been creating areas that are pollinator friendly within the city and uses the Grove Nurseries in Hazelhead to great effect.  A Raised bed planted with a range of pollinator-friendly wildflowers sits outside the poly-tunnel to remember lost ones. This particular bed was created using seed paper hearts on which families and friends who had lost loved ones to overdose had written notes. The area around the poly-tunnels also features shrubs, herb and giant thistles, all of which are a great source for bees and other pollinators.

Recovery Garden Group - overdose hearts

In the city centre, in Carmelite Street the group plants containers in a succession method which provides food for pollinators throughout their life cycle. From spring bulbs through to shrubs and herbs, the group makes a real effort to cover the seasons as best it can.  Flowering pots and perennial shrubs in the Castlegate are also planted up to ensure that nectar sources exist even in the heart of the Granite City.

That ability to make a difference in an urban setting was also a feature of the work of Perth Station Garden Club. The biodiversity garden it has created in Perth’s city railway station includes an orchard area, a wildflower meadow, raised vegetable beds and a lavender edging – all of which is clearly a great resource for pollinators.

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The group is not only keen on gardening but  is noting the species that use the garden; last summer members counted five different species of bumblebee (including tree bumblebees which took a liking to the bird boxes!). Using platform planters, the group has offered nectar and pollen on what would otherwise be sterile platforms. With plans in place to expand  planting next year, this is a wonderful project that could inspire others up and down the country.

Between Perth and Aberdeen, the work of Bonnie Dundee is catching lots of admiring glances. Sowing wildflowers in four large areas (one of which was previously unused) was a huge task. The group appreciates the value of raising awareness and encouraging others to take action, and that the mix of planting and giving advice is a great route to creating more pollinator friendly habitats.

Bonnie Dundee 3

The Dundee group worked around the Overage Shopping Centre and, in engaging local nursery and primary schools, is taking action that will surely deliver future benefits too. With a commitment to promoting the importance of pollinators in both actions and information, this is a group that is hugely impressive in the range of its work.

Watch Us Grow is the catchy name of a garden group based in Cumbernauld. Its organic garden is the hub around which the group provides work opportunities and education for adults with learning disabilities. Concerned by a dearth of pollinators, it set about changing the management of the site, in particular allowing some areas of the grounds to ‘go wild’, thus providing food, shelter and nesting sites for a range of pollinators.


Wildflowers have been sown, a living roof added to a classroom shelter and deadwood left for hibernating insects. With fruit growing areas a central part of the group’s work, this drive to provide for more pollinators is likely to reap rewards.

In the heart of Glasgow’s east end, Allotment Angels of Includeme2 club hosts a growing and gardening project which has transformed a large plot of land in community allotments. Included are several wildflower patches which are proving very popular with bees and butterflies. It’s a biodiversity haven in the midst of a busy part of our largest city and offers an opportunity for youths, adults and young children with additional support needs to engage with nature – which has well documented physical and mental health pluses.

Allotment Angels 1

In Fairlie, Ayrshire, the Organic Growers of Fairlie clearly encourages pollinators in its community garden. Long grass, nettles, providing clover patches for bees and a large wildflower meadow to the front of the group’s garden, it has excelled in providing pollinator friendly habitat. Moreover,  planting is specifically geared to ensuring bees have food sources throughout their life cycle.


With take home messages for members highlighting species, companion planting as well as a connection with the John Muir Awards, the group dove-tails good advice with working across the generations. It’s a wonderful project, with a heavy emphasis on grow your own, enjoy nature and do your bit to help pollinators.

Growing Matters has a similarly connected ethos. A volunteer garden project based in East Lothian – in a formerly derelict walled garden – it strives to increase learning and provide knowledge through gardening.  There is a strong emphasis on recognising the benefits of connecting people and nature, and the project aims to protect physical and mental well-being by encouraging volunteering in what is a peaceful outdoor environment that lets individuals build confidence and learn new skills.

Growing Matters 2

Areas of weeds and long grass are an integral part of the set-up which recognises it can play a role in providing a wildlife corridor. From crocuses to cosmos, from apple trees to verbena, there is a drive to provide forage for pollinators from early spring to late autumn.

Organic Gorwers of Fairlie Nancy MacQueen

However, as you will now appreciate, all of these projects are great examples of communities rallying to help pollinators and people.  It was a pleasure to read about each and every one, and selecting a winner was a near impossible task, so much so that the award was awarded jointly to Organic Growers of Fairlie in North Ayrshire and Growing Matters at Gilmerton Kitchen Garden in East Lothian.  We look forward to following up on their successes and progress over the coming months and years.

Our Living Wall … One Year On

It’s been a great success, staff love it, visitors too … it’s our living wall.  One year on it still offers a thrill, still provides a resource for nature, looks stunning, and everyone loves having their picture taken in front of it.

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A view of the wall in May

From time to time we get requests for information on how the wall came into being, what materials are used, what plants it features, how we water it, what it will look like in future.  So a blog to answer some of those questions seems sensible.

Battleby might on the surface seem a strange venue for a green wall, after all our office is set in beautiful nature-rich grounds.  However, it is as a showcase that Battleby comes into its own. We get a lot of visitors, it’s easy to access the grounds, and you can linger and talk about the wall in ways that might be trickier in a busy urban setting.  So in effect it’s a demonstration site.

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Back in February the wall was pretty subdued looking

The wall structure is interesting. Our living wall used a pre-existing wall for support, but the theory is that most green walls will  utilise an existing vertical space. If not, then a key requirement would be to ensure the wall had sufficient strength to hold the materials (when full laden) which you are going to attach. The rule of thumb for the Fyotextile® system is 35kg per panel when watered and fully grown.

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How things looked back in April as things pick up a little

The covering in which the plants grow is a Fyotextile® semi-hydroponic system.  These pockets hang from rails. The Fyotextile covering comes as a three layer system – a waterproofing layer at the back, a rooting layer on top of this which is made from recycled textile waste and finally a Fyotextile pocket layer which holds the plants.

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We were able to use a pre-existing structure to support the living wall.

Our wall covers 14sq m. Because our wall is near to Battleby House we were able to link into the mains water supply.  Between the supply and the wall we have an on/off tap and  the flow of water is controlled by an electronic timer. Most of the year this comes on as a trickle flow early in the morning and again early in the evening for 10 minutes.  We haven’t extended that often, but in the height of summer we did extend the watering to 15 minutes for a short period.  The water is turned off now and won’t come back on until early spring, in the meantime we will keep a watching brief.

I have had occasions when I’ve resorted to manually watering the wall. Once was before the automatic system was live, and once again when our mains system was out of commission. That involved lots of watering cans and a ladder. It also absorbed a good half-hour and no matter how hard I tried I failed miserably to avoid water running down my sleeve and under my armpits when watering overhead!


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A dash of colour in summer

You might wonder why we don’t simply capture rain water.  We did explore the options but found too many issues. These included challenges around dry periods (we do get them!), concerns about standing water, and the cost of installing a large water tank. The wall is south facing and catches a lot of sunshine, and the overhang of the structure’s roof  means the wall rarely benefits from any downpours,   So it was either manual watering, or latching into our nearby water supply.

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What did we plant in the wall?   A wide mixture of plants. Mostly selected to help pollinators, some had a role to provide cover and shelter for insects, others offered structure or were simply aesthetically pleasing. All of the plants were sourced from Scottish nurseries  and expected to be hardy and thrive in this area. However, we knew from speaking to other living wall owners that we could expect a die-off rate of around 15 to 20%. Fingers-crossed as we haven’t experience that level of loss, although having the talented Jim Carruthers, our hugely popular ‘celebrity’ gardener, on hand clearly helps, as he administers his skills on a regular basis and can spot problems and replace lost causes on his ‘latest baby’.

The plants Jim tends include a mixture of native and non-native species often found in gardens.  Pinks, strawberries, ferns, Campanulas, deadnettles and herbs all rubbing shoulders in a way which allows a close inspection of the flowers and the insects visiting them.  The plant species include Dianthus carthusianorum, Fragaria vesca,  Blechnum spicant (hard fern), Campanula poscharskyana , Dryopteris affinis (golden shield fern), Lamium maculatum Roseum, Aubrieta ‘Hürth’, x Mukgenia ‘Flame’, Liriope muscari ‘Lilac Wonder’, Origanum vulgare ‘Compactum’ and Sedum rupestre ‘Angelina’.  A star of the wall was the spectacularly rampant Polygonum bistorta “Superbum’.

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Manual watering gave the plug plants a good start.

Challenges?  Watering initially was a bind.  Planting less so as colleagues rallied to a planting day (I’d recommend having a small army of helpers on day one), touch wood we haven’t had any pests of note, nor any large or invasive species popping in!

What to expect in future?  Clearly the soil in the pockets will become exhausted so we anticipate needing to feed the wall at some point.  Some plants will gallop on and need a trim, some will need to be split (which might be a good thing when it comes to filling gaps). As in traditional gardening the world over there are no guarantees, so we watch to see what thrives and what suddenly and sometimes inexplicably fails.   The pockets have a lot of life left in them yet but the constant watering, sun-bleaching and seasonal changes will surely take a toll over the years.

Alice B - living wall June

The big question … how different will things look next year ?

It’s been a great project, a thoroughly enjoyable demonstration of what is possible. Here’s hoping it inspires others to follow suit, if they do they, and a host of pollinators, are sure to enjoy.