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Rare harvest mice thriving at RHS Garden Hyde Hall

8 nests belonging to this UK Priority Species discovered in Hyde Hall borders for first time

Horticulturists at RHS Garden Hyde Hall have made the exciting discovery of harvest mouse nests in their borders – a sure sign that there is a breeding population of this increasingly rare native mammal within the garden.

Harvest mice are the smallest rodent in the UK, weighing in at about 5g – equivalent to a two pence piece. The tiny mice use their long tails as an extra limb, helping them to climb up vegetation in their favoured habitat of grasslands, reedbeds and hedgerows. They build their nests within the vegetation, creating dense, tightly woven balls using strands of grasses and reeds.

Though harvest mice will nest in untended grassy areas such as field margins and road verges, it is unusual to find the diminutive mammal in a cultivated garden environment, making this an exciting and encouraging discovery at Hyde Hall.

Due to the mouse’s small size and secretive habits, its populations are often only known through records of its nests, which become more visible in autumn once vegetation dies back. Appearing on the IUCN Red List of Threatened Species, the harvest mouse is also a UK Biodiversity Action Plan (BAP) Priority Species.

At Hyde Hall the first evidence of harvest mice in the cultivated areas of the garden was found within the borders of Clover Hill, when gardeners discovered the nests while cutting back grasses over winter. Clover Hill has large borders, covered in swathes of ornamental grasses and herbaceous perennials, including Calamagrostis, Molinia and Anemanthele. Harvest mice do not use their nests over winter and will build a new nest each spring, with the nesting season lasting from May until October.

The Clover Hill borders at RHS Garden Hyde Hall, where harvest mouse nests were found within the ornamental grasses
In total the garden team have found 8 nests in the borders, indicating that there may be a growing population at Hyde Hall. Nests had previously been found in non-cultivated areas within Hyde Hall’s wider estate, but never in cultivated areas of the garden. Harvest mouse nests were also found at RHS Garden Rosemoor for the first time this year, in the same types of ornamental grass that the nests were found in at Hyde Hall.

You don’t have to have a ‘wildlife garden’ for it to be for wildlife, but you do need to think about what each plant offers and how to manage it

- Sarah Wilson-Frost, Horticulturist at Hyde Hall

These promising finds highlight the importance of cultivated areas for biodiversity, and the potential for gardens to provide a whole ecosystem opportunity for the wide variety of organisms that visit and live in our gardens. 

Harvest mice use their long tails to help them climb and balance
Harvest mouse nest suspended among ornamental grasses in a border on Clover Hill
Hyde Hall horticulturist Sarah Wilson-Frost said: “I was thrilled to find the harvest mice nests over winter, and we continued to find them into spring. We have been able to make changes to the management of the beds to help the mice survive cold winters.

“Rather than removing the ornamental grasses when we cut back in autumn, we are now shredding the material and leaving it on the beds, creating more habitat for invertebrates and overwintering areas for small mammals. This also has the added benefit of improving the soil as nutrients are added as the shredded material rots down. We are also looking at ways to create wildlife corridors through the gardens so creatures can move around under cover.

“Our wider estate is managed for wildlife, and has been ‘rewilded’ from intensive farming to managed woodland and meadows, with connective wildlife corridors of long grass and hedgerows re-established. These wildlife corridors run close to the ornamental parts of the garden.”

RHS Senior Ecologist Gemma Golding said: “It was very exciting to hear that Hyde Hall have found a new species in the garden, and this addition helps to show how important garden habitats can be in boosting biodiversity across the UK.

“Gardens are an important extension of native habitats, and as Hyde Hall is surrounded by farmland, it is likely the mice will have come from there and found suitable food and living space in the garden.”  


What does Hyde Hall offer for harvest mice?

  • Similar grasses to what the mice would find in wilder areas – e.g. evergreen Anemanthele and deciduous Molinia and Calamagrostis. Harvest mice will only use grass they can shred lengthways through their teeth
  • Good food availability – seeds, berries and invertebrates; a rich and biodiverse environment
  • Year-round cover from evergreen grasses, shrubs and winter ground cover
  • Wildlife corridors
  • No pesticides
  • Healthy soils, leading to increased numbers of invertebrates
  • Plant material (seedheads etc.) left standing over winter and not cut back until spring, providing great habitat for insects and small mammals to hibernate and overwinter, while the seeds and berries provide winter food.

Gardens are part of a wider network of green spaces: even a small garden is valuable as part of a much larger web of neighbours’ gardens, which in turn connect with the wider landscape; maybe a local park, road verges or fields. An area of green space such as a garden should not be considered as an isolated unit, but viewed in the context of the wider matrix.

This is evident at Hyde Hall, where the ornamental garden areas are linked to the more natural habitats of the wider estate by habitat corridors such as hedges and long grass, through which harvest mice were able to travel. Habitat corridors, and the opportunity they provide for wildlife to move through the landscape, are key to the success of wildlife populations.


How to help harvest mice

Leaving areas of grass to grow long can provide habitat for harvest mice, along with a wide range of other biodiversity

Gardens are a key extension of native habitats, and this find shows how important garden habitats can be in boosting biodiversity across the UK

- Gemma Golding, RHS Senior Ecologist
If your garden is near farmland, you too could see harvest mice nesting in your garden. If you’d like to give these adorable but increasingly rare mammals a helping hand and encourage them into your own garden, follow these top tips adapted from Suffolk Wildlife Trust.
 
  1. Leave aside some areas of your garden, a minimum of 2m wide, where the grass is allowed to grow without any mowing. If you can, having 3 such areas and cutting one of them each year – so each patch is cut just once every 3 years – will ensure there is always suitable habitat for breeding, feeding and overwintering. Paddocks and wildflower meadows can also provide good habitat.
  2. If you have a pond or part of your garden is close to a ditch, river or any other wet area, allow the surrounding vegetation to grow taller to provide nesting habitat for harvest mice.
  3. Try to link together habitat areas with corridors of long grass, so populations do not become isolated.
  4. If you’re planting trees, allow the grass around them to grow long to provide a new habitat as the trees grow. If you're planting many trees, try to include clearings or margins where the trees will not shade out the grasses, and keep those as long grass habitat.
  5. If you have space, you can sow an area of your garden with a wild bird crop or a cover crop mix containing millet. As well as benefitting birds, this is ideal for harvest mice to nest and feed in.

Areas of long grass with paths mown through at RHS Garden Hyde Hall

As custodians of green space – even if it’s a tiny back garden – we all have a responsibility to increase biodiversity, and can all do our bit

- Sarah Wilson-Frost, Horticulturist at Hyde Hall

RHS Hyde Hall now practice chop and drop to provide better continuity of habitat for the harvest mice. Read our guide to find out why you should try this time-saving, wildlife-benefitting technique at home.

About the author – Olivia Drake

With a background in biology, Olivia is passionate about sustainable horticulture, biodiversity and the role gardening can play in conservation. She is trained as a botanical horticulturist and previously worked in public gardens around the UK and abroad.

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Anemanthele lessoniana
pheasant's tail grass
  • 0.5–1 metres
  • 1–1.5 metres
<em>Anemanthele</em> <em>lessoniana</em>
Molinia caerulea
purple moor-grass
  • 0.5–1 metres
  • 0.5–1 metres
<em>Molinia</em> <em>caerulea</em>
Calamagrostis × acutiflora 'Karl Foerster'
feather reed grass 'Karl Foerster'
  • 1–1.5 metres
  • 0.5–1 metres
<em>Calamagrostis</em> × <em>acutiflora</em> 'Karl Foerster'
Anemanthele lessoniana
pheasant's tail grass
  • 0.5–1 metres
  • 1–1.5 metres
<em>Anemanthele</em> <em>lessoniana</em>
Molinia caerulea
purple moor-grass
  • 0.5–1 metres
  • 0.5–1 metres
<em>Molinia</em> <em>caerulea</em>
Calamagrostis × acutiflora 'Karl Foerster'
feather reed grass 'Karl Foerster'
  • 1–1.5 metres
  • 0.5–1 metres
<em>Calamagrostis</em> × <em>acutiflora</em> 'Karl Foerster'
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