Fleam Dyke

Site of Special Scientific Interest · 52.1501, 0.2874

Also within

Cambridgeshire County

Condition (Natural England)

Unfavourable Recovering (2) Unfavourable No Change (1)
UnitFeatureConditionArea (ha)Assessed
TL542548 Unfavourable Recovering 5.18 2012-12-07
TL553536 Unfavourable Recovering 3.99 2012-12-07
TL565526 Unfavourable No Change 2.59 2012-12-07

Geology & landscape

Rock Type: Chalk, Glacial Till

Landscape processes: Glacial, Volcanic / Igneous

Description

Area, 24 hectares 59 ac Description The Fleam Dyke holds chalk scrub and species rich chalk grassland communities which are of a very limited distribution in south, central and eastern England and especially rare in Cambridgeshire. The site is a linear earthwork which dates back to at least the seventh Century and extends across the open chalklands from the Fens to the formerly heavily wooded Boulder Clay. Of prime importance is the species rich chalk grassland which, once extensive in the area and maintaine dby grazing, is now restricted to the steep banks of this ancient earthwork and is now maintained by cutting. The grassland community is characterised by the presence of such species as upright brome Bromus erectus, meadow oat grass Avenula pratensis and crested hair grass Koeleria macrantha. Associated herbs include dropwort Filipendula vulgaris and purple milk vetch Astragalus danicus. Areas of the Dyke are covered by calcareous scrub which has developed over formerly open grassland. hawthorn Crataegus monogyna forms dense thickets but many other shrub species are present. Of particular note is the presence of juniper Juniperus communis, a species which is rare in the region and for which Fleam Dyke is the only Cambridgeshire site. The invertebrate and bird life enhance the interest of the Dyke.

Species mentioned

English name
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Latin name
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IUCN / Red List Type Family
meadow oat grass Avenula pratensis Not listed in GB list grass poaceae
upright brome Bromus erectus Not listed in GB list grass poaceae
crested hair-grass Koeleria macrantha NT grass poaceae
purple milk vetch Astragalus danicus EN herb fabaceae
dropwort Filipendula vulgaris LC herb rosaceae
hawthorn Crataegus monogyna LC shrub rosaceae
juniper Juniperus communis CR shrub cupressaceae

Insects to look out for

These moths, butterflies and beetles are known to feed on plants recorded at this site, and carry a notable UK conservation status — but a host-plant being present doesn't mean the insect has actually been recorded here. Treat this as "worth watching for," not a confirmed sighting.

SpeciesStatusVia host-plant
Figure of eight
Diloba caeruleocephala
Endangered Crataegus spp.
The lappet
Gastropacha quercifolia
Endangered Crataegus monogyna
Scarce vapourer
Orgyia recens
Endangered Crataegus spp.
Mouse moth
Amphipyra tragopoginis
Vulnerable Crataegus spp.
The sprawler
Asteroscopus sphinx
Vulnerable Crataegus spp.
Mottled umber
Erannis defoliaria
Vulnerable Crataegus spp.
Juniper pug
Eupithecia pusillata
Vulnerable Juniperus communis, Juniperus spp.
The lackey
Malacosoma neustria
Vulnerable Crataegus monogyna
Pale brindled
Phigalia pilosaria
Vulnerable Crataegus monogyna
Early moth
Theria primaria
Vulnerable Crataegus monogyna
Pale eggar
Trichiura crataegi
Vulnerable Crataegus monogyna
Flounced chestnut
Agrochola helvola
Near Threatened Crataegus monogyna
Beaded chestnut
Agrochola lychnidis
Near Threatened Crataegus monogyna
Grey chi
Antitype chi
Near Threatened Crataegus monogyna
Large thorn
Ennomos autumnaria
Near Threatened Crataegus spp.
Grey pug
Eupithecia subfuscata
Near Threatened Crataegus monogyna
Double dart
Graphiphora augur
Near Threatened Crataegus spp.
The blackneck
Lygephila pastinum
Near Threatened Astragalus spp.

Host-plant data: Cook et al. (2025), Traits data for the butterflies and macro-moths of Great Britain and Ireland, 2024, UK Centre for Ecology & Hydrology / Butterfly Conservation; and Padovani et al. (2020), Database of Insects and their Food Plants (DBIF), UK Centre for Ecology & Hydrology (both Open Government Licence). Contains data supplied by UK Centre for Ecology & Hydrology.

Plant communities

W21 — Hedgerow scrub, Mixed scrub

Crataegus monogyna-Hedera helix scrub

Matches 2 species from the description above: Crataegus monogyna, Juniperus communis

Hedera helix, Salix cinerea, Acer pseudoplatanus, Ilex aquifolium, Betula pendula, Corylus avellana, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Malus sylvestris, Sorbus aria, Taxus baccata, Ulmus glabra, Ulmus procera, Sambucus nigra, Viburnum lantana, Euonymus europaeus, Cornus sanguinea, Juniperus communis, Ligustrum vulgare, Clematis vitalba, Rhamnus cathartica, Crataegus laevigata, Crataegus monogyna, Prunus spinosa, Juncus effusus, Plagiomnium undulatum, Brachythecium rutabulum, Kindbergia praelonga, Rhynchostegium confertum, Tamus communis, Heracleum sphondylium, Torilis japonica, Arum maculatum, Arctium minus, Cirsium arvense, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Stellaria graminea, Stellaria holostea, Stellaria media agg., Calystegia sepium, Mercurialis perennis, Geranium robertianum, Iris foetidissima, Glechoma hederacea, Lamium purpureum, Origanum vulgare, Stachys sylvatica, Teucrium scorodonia, Allium ursinum, Hyacinthoides non-scripta, Circaea lutetiana, Rumex sanguineus, Anemone nemorosa, Ranunculus repens, Fragaria vesca, Geum urbanum, Potentilla sterilis, Poterium sanguisorba, Rosa arvensis, Rosa canina, Rubia peregrina, Rubus fruticosus agg., Galium aparine, Urtica dioica, Viola riviniana, Anisantha sterilis, Arrhenatherum elatius, Brachypodium pinnatum, Brachypodium sylvaticum, Bromopsis erecta, Dactylis glomerata, Elytrigia repens, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris filix-mas

W20 — Montane scrub

Salix lapponum-Luzula sylvatica scrub

Salix arbuscula, Salix cinerea, Salix lapponum, Salix myrsinites, Salix phylicifolia, Salix reticulata, Empetrum nigrum, Calluna vulgaris, Salix lanata, Vaccinium myrtillus, Vaccinium uliginosum, Carex atrata, Carex bigelowii, Carex binervis, Carex flacca, Luzula multiflora, Luzula sylvatica, Huperzia selago, Selaginella selaginoides, Aulacomnium palustre, Mnium hornum, Philonotis fontana, Plagiomnium undulatum, Rhizomnium punctatum, Dicranum bonjeanii, Dicranum majus, Dicranum scoparium, Fissidens adianthoides, Racomitrium lanuginosum, Calliergonell cuspidatum, Ctenidium molluscum, Hylocomium splendens, Hypnum callichroum, Hypnum cupressiforme, Palustriella commutatum, Plagiothecium denticulatum, Plagiothecium undulatum, Pleurozium schreberi, Ptilium crista-castrensis, Rhytidiadelphus loreus, Rhytidiadelphus squarrosus, Rhytidiadelphus triquetrus, Sanionia uncinata, Scorpidium revolvens, Thuidium tamariscinum, Atrichum undulatum, Polytrichastrum alpinum, Sphagnum capillifolium, Sphagnum fallax, Sphagnum girgensohnii, Sphagnum palustre, Sphagnum russowii, Sphagnum squarrosum, Sphagnum subnitens, Sphagnum teres, Barbilophozia barbata, Chiloscyphus polyanthos, Diplophyllum albicans, Lophocolea bidentata, Plagiochila porelloides, Ptilidium ciliare, Scapania undulata, Cladonia squamosa, Peltigera canina, Angelica sylvestris, Caltha palustris, Hieraclium spp., Saussurea alpina, Solidago virgaurea, Campanula rotundifolia, Succisa pratensis, Valeriana officinalis, Rhodiola rosea, Vaccinium vitis-idaea, Thymus praecox, Epilobium anagallidifolium, Dactylorhiza viridis, Euphrasia officinalis, Rhinanthus minor, Oxalis acetosella, Oxyria digyna, Polygonum viviparum, Rumex acetosa, Anemone nemorosa, Ranunculus acris, Thalictrum alpinum, Alchemilla alpina, Alchemilla glabra, Filipendula ulmaria, Geum rivale, Galium boreale, Galium saxatile, Saxifraga aizoides, Saxifraga hypnoides, Saxifraga oppositifolia, Saxifraga stellaris, Viola riviniana, Agrostis canina, Agrostis capillaris, Anthoxanthum odoratum, Deschampsia cespitosa, Deschampsia flexuosa, Festuca ovina, Festuca rubra, Nardus stricta, Dryopteris dilatata, Phegopteris connectilis

W22 — Hedgerow scrub, Mixed scrub

Prunus spinosa-Rubus fruticosus scrub

Hedera helix, Acer campestre, Corylus avellana, Ulex europaeus, Prunus spinosa, Plagiomnium undulatum, Brachythecium rutabulum, Eurhynchium striatum, Kindbergia praelonga, Thuidium tamariscinum, Atrichum undulatum, Lophocolea bidentata, Achillea millefolium, Cardamine flexuosa, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Silene uniflora, Stellaria media agg., Mercurialis perennis, Geranium robertianum, Stachys sylvatica, Teucrium scorodonia, Hyacinthoides non-scripta, Oxalis acetosella, Digitalis purpurea, Plantago lanceolata, Veronica chamaedrys, Armeria maritima, Rumex acetosa, Filipendula ulmaria, Geum urbanum, Rosa canina, Rubus fruticosus agg., Rubus idaeus, Galium aparine, Urtica dioica, Viola riviniana, Agrostis capillaris, Brachypodium sylvaticum, Dactylis glomerata, Festuca rubra, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris borreri, Dryopteris filix-mas