List of Sites of Special Scientific Interest in Hertfordshire

This article is about SSSIs in Hertfordshire. For other counties, see List of SSSIs by Area of Search.

Tring Reservoirs at sunrise

Hertfordshire is a county in eastern England. It is bordered by Bedfordshire to the north, Cambridgeshire to the north-east, Essex to the east, Buckinghamshire to the west and Greater London to the south. The county town is Hertford. As of 2018, the county has a population of 1,184,400 ^[1] in an area of 634 square miles (1,640 km²). ^[2]

As of July 2019, there are 43 sites designated within this Area of Search, 36 of which have been designated for their biological interest and 7 for their geological interest. ^[3] In England the body responsible for designating SSSIs is Natural England, which chooses a site "because of its flora, fauna, or geological or physiographical features". ^[4]

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Key

Interest

• B = a site of biological interest
• G = a site of geological interest

Other classifications

• CAONB = Chilterns Area of Outstanding Natural Beauty
• GCR = Geological Conservation Review
• EWT = Essex Wildlife Trust
• HMWT = Herts and Middlesex Wildlife Trust
• LNR = Local nature reserve
• NCR = A Nature Conservation Review
• NNR = National nature reserve
• NT = National Trust
• Ramsar = Ramsar site
• RHPG = Register of Historic Parks and Gardens of Special Historic Interest in England
• RSPB = Royal Society for the Protection of Birds
• SM = Scheduled monument
• SPA = Special Protection Area
• WT = Woodland Trust

Sites

Site name	Photograph	B	G	Area [lower-alpha 1]	Public access	Location [lower-alpha 1]	Other classifications	Map [lower-alpha 1]	Citation [lower-alpha 1]	Description
Aldbury Nowers		Y		19.8 hectares (49 acres)	YES	Tring 51°48′43″N0°37′19″W / 51.8120°N 0.6219°W / 51.8120; -0.6219 (Aldbury Nowers) SP951135	HMWT [5]	Map	Citation	The site hosts the flowers of chalk grassland and has butterfly habitats with several different species of butterfly including the Duke of Burgundy, hairstreaks and the Essex skipper. There are also large areas of woodland and calcareous grassland. [6] [7]
Alpine Meadow		Y		0.8 hectares (2.0 acres)	YES	Berkhamsted 51°46′57″N0°34′04″W / 51.7826°N 0.5677°W / 51.7826; -0.5677 (Alpine Meadow) SP989103	HMWT [8]	Map	Citation	This steeply sloping small meadow is a rare example of unimproved chalk grassland. Grass species include upright brome, false brome and sheep's fescue, and there are many orchids, especially common twayblade and common spotted orchid. [9]
Amwell Quarry		Y		37.1 hectares (92 acres)	YES	Great Amwell 51°47′52″N0°00′16″W / 51.7978°N 0.0045°W / 51.7978; -0.0045 (Amwell Quarry) TL377129	HMWT, [10] SPA, SPA [11] Ramsar [12]	Map	Citation	This is an internationally important site for wintering wildfowl, and is Britain's most important site for dragonflies. Plants include marsh dock and hairlike pondweed, both nationally rare. Amwell has a quarter of all British species of molluscs. [10] [13]
Ashridge Commons & Woods		Y		627.3 hectares (1,550 acres)	YES	Little Gaddesden 51°48′42″N0°35′14″W / 51.8116°N 0.5871°W / 51.8116; -0.5871 (Ashridge Commons & Woods) SP975135	CAONB, [14] NT [14]	Map	Citation	Ths site is mainly semi-natural vegetation, with has extensive areas of woodland, grass and scrub. There are many species of breeding birds, including some which are rare nationally, such as firecrests. Other species which are rare in Hertfordshire are common redstart, nightingale and wood warbler. [15]
Ashwell Springs		Y		0.3 hectares (0.74 acres)	YES	Ashwell 52°02′32″N0°08′59″W / 52.0421°N 0.1497°W / 52.0421; -0.1497 (Ashwell Springs) TL270398		Map	Citation	The site consists of a series of freshwater springs, which provide a habitat for cold water, invertebrate animals, some of which are rare. The site is particularly important for flatworms, including Crenobia alpina and the Polycelis felina. [16]
Benington High Wood		Y		20.7 hectares (51 acres)	YES	Benington 51°53′43″N0°08′02″W / 51.8952°N 0.1339°W / 51.8952; -0.1339 (Benington High Wood) TL285235		Map	Citation	The site is ancient woodland, described by Natural England as "one of the best remaining examples in the county of the pedunculate oak-hornbeam of the ash-maple variety". Shrub species include field maple and hazel, with a higher ground flora diversity in clearings and rides. [17]
Blagrove Common		Y		5.0 hectares (12 acres)	YES	Sandon 51°59′12″N0°04′13″W / 51.9868°N 0.0704°W / 51.9868; -0.0704 (Blagrove Common) TL326338	HMWT [18]	Map	Citation	The site is one of the few areas of unimproved marshy grassland in east Hertfordshire. It is crossed by a stream and has a rich diversity of vegetation, including a variety of orchids. [19] Kestrels often hunt mice and voles, which are common on the site. [18]
Bricket Wood Common		Y		75.5 hectares (187 acres)	YES	Bricket Wood 51°41′47″N0°21′59″W / 51.6964°N 0.3664°W / 51.6964; -0.3664 (Bricket Wood Common) TL130010		Map	Citation	The common is a remnant of a lowland heath, with much it on the heavy soils of boulder clay which have poor drainage and wet habitats. There are also areas of ancient woodland and dry heath. In drier heath areas there are heather, purple moor-grass and heath milkwort. [20]
Castle Lime Works Quarry			Y	1.4 hectares (3.5 acres)	NO	South Mimms 51°42′31″N0°13′22″W / 51.7087°N 0.2227°W / 51.7087; -0.2227 (Castle Lime Works Quarry) TL229026	GCR [21]	Map	Citation	Natural England states: "This reveals extensive piping in the top of the chalk resulting from solution at the Chalk - Tertiary sediment interface. Believed to have formed during the Tertiary and Pleistocene, it is the finest exposure of clay-filled pipes in the Chalk Karst of England." [22]
Croxley Common Moor		Y		39.6 hectares (98 acres)	YES	Croxley Green 51°38′33″N0°26′11″W / 51.6425°N 0.4363°W / 51.6425; -0.4363 (Croxley Common Moor) TQ083949	LNR [23]	Map	Citation	The site is mainly grass heathland with some ancient woodland and hazel coppice. Over 250 species of plants have been recorded, including sheep sorrel, common bent and sheep's fescue. There are many ant hills made by yellow meadow ants. [24] [23]
Downfield Pit, Westmill			Y	0.3 hectares (0.74 acres)	YES	Ware 51°49′51″N0°02′37″W / 51.8308°N 0.0437°W / 51.8308; -0.0437 (Downfield Pit, Westmill) TL349165		Map	Citation	The site provides an example of the complex sequence of Pleistocene gravels and clays laid down by the River Thames when it flowed through the Vale of St Albans before the river was diverted south by the Anglian ice age around 450,000 years ago. [25]
Frogmore Meadows		Y		4.6 hectares (11 acres)	YES	Chenies 51°40′47″N0°31′29″W / 51.6796°N 0.5247°W / 51.6796; -0.5247 (Frogmore Meadows) TQ021989	CAONB, [26] HMWT, [27]	Map	Citation	The site has marshy areas and fens next to the river, damp grassland and drier, more acidic areas. The river bank has water voles, and damp areas are dominated by meadow foxtail and Yorkshire fog, with some marsh marigold and marsh bedstraw. [28] [27]
Great Hormead Park		Y		15.0 hectares (37 acres)	YES	Great Hormead 51°56′36″N0°03′42″E / 51.9432°N 0.0616°E / 51.9432; 0.0616 (Great Hormead Park) TL418292		Map	Citation	The site is coppiced ancient woodland on boulder clay. It has diverse tree species, including wych elm and hornbeam, resulting in a rich ground flora. Dog's mercury is dominant over most of the woodland floor, with plants such as angelica sylvestris and tufted hair grass in wetter areas. [29]
Hertford Heath		Y		29.1 hectares (72 acres)	YES	Hertford Heath 51°46′53″N0°02′14″W / 51.7813°N 0.0372°W / 51.7813; -0.0372 (Hertford Heath) TL355110 & TL350106	HMWT [30]	Map	Citation	The heath is dominated by heather, and there are grass snakes and slow worms. Sphagnum mosses and creeping willow are found in wetter areas. Ponds support the rare water violet and a rich invertebrate fauna such as great crested and smooth newts, the water spider and eight species of dragonfly. [31] [30]
Hillcollins Pit			Y	0.2 hectares (0.49 acres)	YES	Furneux Pelham 51°55′16″N0°05′43″E / 51.9211°N 0.0954°E / 51.9211; 0.0954 (Hillcollins Pit) TL442268	GCR [32]	Map	Citation	This disused gravel pit is the type site for the Westland Green Gravels, which were laid down by the ancestral River Thames 1.6 to 1.8 million years ago, and which show the river's ancient course. [33]
Hunsdon Mead		Y		34.2 hectares (85 acres)	YES	Harlow 51°46′47″N0°03′15″E / 51.7797°N 0.0541°E / 51.7797; 0.0541 (Hunsdon Mead) TL418110	HMWT [34]	Map	Citation	This is unimproved grassland which is subject to winter flooding. Notable grass species include meadow brome and the quaking grass briza media, and there are other unusual flora such as pepper saxifrage and green-winged orchid. [35]
Knebworth Woods		Y		128.8 hectares (318 acres)	YES	Stevenage 51°53′09″N0°13′02″W / 51.8857°N 0.2172°W / 51.8857; -0.2172 (Knebworth Woods) TL228223		Map	Citation	The wood is ancient in origin and ecologically diverse. The dominant trees are oak and hornbeam. Ponds have unusual plant species, and the site is rich in fungi and bryophytes. Breeding birds include nightingales. [36]
Little Heath Pit			Y	1.2 hectares (3.0 acres)	YES	Potten End 51°45′48″N0°31′40″W / 51.7633°N 0.5278°W / 51.7633; -0.5278 (Little Heath Pit) TL017082	GCR, [37] NT [38]	Map	Citation	The lowest layer is gravel dating to the beginning of the Pleistocene 2.6 million years ago. A higher layer of gravel was laid down some 20,000 years ago, when the last ice age was at its maximum, and the site was cold tundra like western Siberia today. [39]
Moor Hall Meadows		Y		24.0 hectares (59 acres)	YES	Ardeley 51°55′16″N0°04′03″W / 51.9211°N 0.0674°W / 51.9211; -0.0674 (Moor Hall Meadows) TL330265		Map	Citation	The site has a variety of types of meadows, with marshy grassland being the most extensive. Its rich flora makes it one of the most important grassland sites in the county. There is also a small ancient woodland which has a variety of breeding birds. [40]
Moor Mill Quarry, West			Y	0.2 hectares (0.49 acres)	NO	How Wood 51°42′43″N0°21′02″W / 51.7119°N 0.3506°W / 51.7119; -0.3506 (Moor Mill Quarry, West) TL141027	GCR [41]	Map	Citation	The pit displays the advance of ice during the Anglian glaciation around 450,000 years ago, which diverted the Thames south to its present course. The site is regarded by Natural England as of fundamental importance as the only one which demonstrates the diversion of the Thames from its pre-Anglian course. [42]
Northaw Great Wood		Y		224.3 hectares (554 acres)	YES	Cuffley 51°43′22″N0°08′54″W / 51.7228°N 0.1483°W / 51.7228; -0.1483 (Northaw Great Wood) TL280043	LNR [43]	Map	Citation	The site has one of the county's most extensive areas of ancient hornbeam woodland, with other trees including oak and silver birch. Glades, streams and springs add to the biodiversity. [44]
Oddy Hill and Tring Park		Y		36.0 hectares (89 acres)	YES	Tring 51°47′20″N0°38′50″W / 51.7890°N 0.6473°W / 51.7890; -0.6473 (Oddy Hill) SP934109 51°47′01″N0°39′22″W / 51.7837°N 0.6561°W / 51.7837; -0.6561 (Tring Park) SP928103	RHPG. [45]	Map	Citation	This is one of the most extensive areas of unimproved chalk downland in Hertfordshire. The site has diverse grass and flowering plant species. Orchids include common spotted-orchid, common twayblade, greater butterfly-orchid and southern marsh-orchid. [46]
Oughtonhead Lane			Y	1.0 hectare (2.5 acres)	YES	Hitchin 51°57′19″N0°17′45″W / 51.9552°N 0.2959°W / 51.9552; -0.2959 (Oughtonhead Lane) TL172299	GCR [47]	Map	Citation	The site probably dates to the Hoxnian interglacial 420,000 to 300,000 years ago. It was then a marsh fed by springs, and it has a tufa which contains fossil land snails and mammal bones which show the climate and local environmental conditions. [48]
Patmore Heath		Y		8.5 hectares (21 acres)	YES	Albury 51°54′43″N0°05′47″E / 51.9120°N 0.0965°E / 51.9120; 0.0965 (Patmore Heath) TL443258	HMWT [49]	Map	Citation	The site is home to a large amount of dry grass, as well as marshy-areas. Much of the turf is dominated by Deschampsia, as well as occurrences of Anthoxanthum odoratum. Uncommon plants are heath rush and heath grass. There are a wide variety of dragonfly, including the emperor dragonfly. [50]
Plashes Wood		Y		73.2 hectares (181 acres)	YES	Standon 51°52′01″N0°00′21″E / 51.8669°N 0.0058°E / 51.8669; 0.0058 (Plashes Wood) TL382206		Map	Citation	The site is mainly oak and hornbeam woodland near the northern limit of its natural distribution. It has varied ground flora on soils from damp heavy clay to light gravels. There are also ponds and extensive clearings dominated by bracken, and other flora including hoary cinquefoil. [51]
Redwell Wood		Y		52.6 hectares (130 acres)	YES	South Mimms 51°42′29″N0°14′45″W / 51.7081°N 0.2459°W / 51.7081; -0.2459 (Redwell Wood) TL213025		Map	Citation	The site has ancient and secondary woodland, heath and scrub. The woodland canopy is dominated by pedunculate oak. Ground flora include bluebells and enchanter's-nightshade, while heathland species include heather and the rare creeping willow. [52]
Roughdown Common		Y		3.7 hectares (9.1 acres)	YES	Hemel Hempstead 51°44′25″N0°29′06″W / 51.7402°N 0.4850°W / 51.7402; -0.4850 (Roughdown Common) TL047057	CAONB [53]	Map	Citation	This is one of the few examples of unimproved calcareous grassland in Hertfordshire. The dominant grasses are meadow fescue and meadow oat-grass, and there are colonies of orchids. It is the only site in the county where common juniper regenerates naturally. [54] [53]
Rye Meads		Y		60.3 hectares (149 acres)	YES	Rye House 51°46′34″N0°00′22″E / 51.7760°N 0.0061°E / 51.7760; 0.0061 (Rye Meads) TL385105	Ramsar, [55] SPA [11] RSPB, [55] HMWT [56]	Map	Citation	Part of this site is an ancient flood meadow which has a variety of habitats including reedbed, marshy grassland and fen. It is grazed by ponies and water buffalo. [56] There are also ponds which have kingfisher, snipe, green sandpiper, shoveler, gadwall and tufted duck. [57]
Sarratt Bottom		Y		3.5 hectares (8.6 acres)	NO	Sarratt 51°40′46″N0°30′37″W / 51.6794°N 0.5102°W / 51.6794; -0.5102 (Sarratt Bottom) TQ031989		Map	Citation	The site is a meadow beside the River Chess. It is an example of damp grassland which has been traditionally managed for grazing. There are also areas of swamp and marsh. The main plants in grassland areas include sweet vernal grass and meadow foxtail, and marsh horsetail and common spike-rush are common in damper areas. [58]
Sawbridgeworth Marsh		Y		6.2 hectares (15 acres)	YES	Sawbridgeworth 51°49′15″N0°09′48″E / 51.8209°N 0.1634°E / 51.8209; 0.1634 (Sawbridgeworth Marsh) TL492158	EWT [59]	Map	Citation	The site is a river valley marsh close to the River Stort, which has a varied wetland flora. Grazing and cutting of the marsh in rotation maintain biological diversity. The site also has an important wetland fauna and many moth species. [60]
Sherrardspark Wood		Y		74.4 hectares (184 acres)	YES	Welwyn Garden City 51°48′37″N0°13′02″W / 51.8102°N 0.2172°W / 51.8102; -0.2172 (Sherrardspark Wood) TL230139	LNR [61]	Map	Citation	The site is an ancient semi-natural sessile oak and hornbeam wood on acid soils. There are also swallowholes fed by streams, and a woodland ride provides a habitat for invertebrates. [62]
Tewinbury		Y		7.3 hectares (18 acres)	NO	Tewin 51°48′34″N0°10′04″W / 51.8095°N 0.1679°W / 51.8095; -0.1679 (Tewinbury) TL264139	HMWT [63]	Map	Citation	The site borders the River Mimram. It has alluvial meadows and marshes which are rare in lowland Britain. There are areas of swamp and tall fens, with plants including butterbur and angelica. Otters have been observed on the riverbank, in possibly the only site in the county. [64] [63]
Therfield Heath		Y		146.5 hectares (362 acres)	YES	Therfield 52°02′32″N0°03′18″W / 52.0423°N 0.0549°W / 52.0423; -0.0549 (Therfield Heath) TL335400	LNR, [65] SM [66] [67]	Map	Citation	This site is described by Natural England as describing some to the richest chalkland in England. It is unimproved pasture which has a wide variety of plants including the rare pasque flower. There is a diverse insect fauna. [68]
Thorley Flood Pound		Y		17.3 hectares (43 acres)	YES	Thorley 51°50′36″N0°09′41″E / 51.8434°N 0.1615°E / 51.8434; 0.1615 (Thorley Flood Pound) TL490183	HMWT [69]	Map	Citation	Habitats include tall wash grassland, which is now rare, marsh and waterlogged grassland. It has a wide variety of plant species, including reed sweet-grass and meadowsweet. There are flowers such as fen bedstraw and early marsh orchid. Breeding birds include snipe and water rails. [70]
Tring Reservoirs		Y		100.0 hectares (247 acres)	YES	Tring 51°48′49″N0°40′06″W / 51.8135°N 0.6683°W / 51.8135; -0.6683 (Tring Reservoirs) SP919136 SP905131	HMWT [71]	Map	Citation	These four reservoirs are on the sites of ancient marshes, and their diverse fauna and flora include some dating back to their marshland origins. The site is important for breeding and wintering birds, including nationally important numbers of shovelers. The site is also significant for invertebrates. [72]
Tring Woodlands		Y		24.1 hectares (60 acres)	YES	Tring 51°46′52″N0°40′20″W / 51.7812°N 0.6721°W / 51.7812; -0.6721 (Tring Woodlands) SP917100	CAONB [73]	Map	Citation	The wood has a rich flora, showing that it is well established. It is one of the best examples of semi-natural beech woodland in Hertfordshire. Plants include woodruff, wood anemone and dog's mercury, and there is a variety of woodland birds. [74]
Turnford and Cheshunt Pits		Y		174.4 hectares (431 acres)	YES	Cheshunt 51°42′32″N0°01′07″W / 51.7090°N 0.0186°W / 51.7090; -0.0186 (Turnford & Cheshunt Pits) TL370030	SPA [11]	Map	Citation	This site includes ten former gravel pits, which are of national importance for wintering gadwalls and shovelers. It is also valuable for invertebrates, especially grasshoppers and bush-crickets. [75]
Wain Wood		Y		19.0 hectares (47 acres)	YES	Preston 51°54′56″N0°17′09″W / 51.9155°N 0.2858°W / 51.9155; -0.2858 (Wain Wood) TL180255		Map	Citation	The wood lies on a north-east facing slope of decalcified boulder clay. The woodland area is also home to pedunculate oak and Quercus petraea , with much of the south of the area consisting of acidic grassland. There are many butterfly species, including Thecla quercus . [76]
Water End Swallow Holes		Y		11.1 hectares (27 acres)	YES	Welham Green 51°43′26″N0°13′14″W / 51.7239°N 0.2206°W / 51.7239; -0.2206 (Water End Swallow Holes) TL230043		Map	Citation	The site covers more than fifteen sinkholes, the only ones in chalk which are a permanent feature of the landscape. Next to the holes is a swamp area of willow carr which is biologically important, and in deep water there is reed sweet-grass. The site also has areas of woodland and grassland. [77]
Westwood Quarry			Y	0.1 hectares (0.25 acres)	NO	Watford 51°40′56″N0°27′08″W / 51.6823°N 0.4523°W / 51.6823; -0.4523 (Westwood Quarry) TQ071993	GCR [78]	Map	Citation	This site throws light on the early history of the River Thames, when it flowed through the Vale of St Albans, before it was diverted south to its present course during the Anglian Ice Age around 450,000 years ago. [79]
Whippendell Wood		Y		66.7 hectares (165 acres)	YES	Watford 51°40′07″N0°26′44″W / 51.6687°N 0.4455°W / 51.6687; -0.4455 (Whippendell Wood) TQ076978		Map	Citation	This is ancient woodland, and the main trees are oak, ash, hazel and hornbeam. Ground flora include Yorkshire fog, bluebells and honeysuckle. There are diverse species of fungi, invertebrates and birds. [80]
Wormley-Hoddesdonpark Wood North		Y		143.9 hectares (356 acres)	YES	Hoddesdon 51°45′32″N0°02′33″W / 51.7589°N 0.0425°W / 51.7589; -0.0425 (Wormley-Hoddesdonpark Wood North) TL352085 TL325075	NNR, [81] WT, [81] NCR , [82] HMWT, [83] SAC [84]	Map	Citation	The site is oak and hornbeam on acid gravel. The ground flora is diverse, including dog's mercury and yellow archangel. Small ponds and streams are important for bryophytes, and invertebrates include the green tiger beetle. [82]
Wormley-Hoddesdonpark Wood South		Y		196.2 hectares (485 acres)	YES	Cheshunt 51°44′39″N0°04′25″W / 51.7441°N 0.0735°W / 51.7441; -0.0735 (Wormley-Hoddesdonpark Wood South) TL331068	NNR, [85] NCR , [86] SAC [84]	Map	Citation	The site is oak and hornbeam woodland mainly on London clay. Plants in the variable ground flora include brambles, wood anemones and bluebells. Other habitats include marshland and acidic grassland. [86]

Wikimedia Commons has media related to Sites of Special Scientific Interest in Hertfordshire .

See also

• Herts and Middlesex Wildlife Trust
• List of Local Nature Reserves in Hertfordshire

Notes

1. Maps and citations for each site are taken from the Natural England database. The area and location of the site is shown on the citation. The listing is as in January 2016.

References

1. "People and Place". Herts Insight. Retrieved 23 July 2019.
2. "Area Measurements". Hertfordshire Local Information System. Archived from the original on 10 February 2015. Retrieved 10 February 2015.
3. "Designated Sites View - Hertfordshire". Natural England. Retrieved 23 July 2019.
4. "Guidelines for selection of biological SSSIs". Joint Nature Conservation Committee. Archived from the original on 23 January 2016. Retrieved 12 January 2016.
5. "Aldbury Nowers". Herts and Middlesex Wildlife Trust. Archived from the original on 5 September 2015. Retrieved 11 January 2016.
6. "Aldbury Nowers" (PDF). Natural England. Archived from the original (PDF) on 20 March 2009. Retrieved 21 February 2006.
7. "Aldbury Nowers". Herts and Middlesex Wildlife Trust. Archived from the original on 23 July 2011. Retrieved 7 January 2011.
8. "Alpine Meadow". Hertfordshire and Middlesex Wildlife Trust. Archived from the original on 21 December 2014. Retrieved 21 December 2014.
9. "Alpine Meadow citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 21 December 2014.
10. "Amwell". Hertfordshire and Middlesex Wildlife Trust. Archived from the original on 19 April 2015. Retrieved 19 December 2014.
11. "Lee Valley". Joint Nature Conservation Committee. Archived from the original on 26 October 2016. Retrieved 16 January 2016.
12. "Lee Valley". Ramsar Sites Information Service. Archived from the original on 20 December 2014. Retrieved 19 December 2014.
13. "Amwell Quarry citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 24 September 2015. Retrieved 19 December 2014.
14. "Ashridge Commons and Woods citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 4 January 2016.
15. "Ashridge Commons & Woods citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 19 December 2014.
16. "Ashwell Springs citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 12 January 2015.
17. "Benington High Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 3 January 2015.
18. "Blagrove Common". Hertfordshire and Middlesex Wildlife Trust. Archived from the original on 23 December 2014. Retrieved 12 January 2015.
19. "Blagrove Common citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 12 January 2015.
20. "Bricket Wood Common citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 7 December 2014.
21. "Castle Lime Works Quarry (Karst)". Joint Nature Conservation Committee. Archived from the original on 4 March 2016. Retrieved 11 January 2016.
22. "Castle Lime Works Quarry citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 15 January 2015.
23. "Croxley Common Moor". Local Nature Reserves. Natural England. 13 March 2013. Archived from the original on 9 August 2014. Retrieved 10 December 2014.
24. "Croxley Common Moor citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 10 December 2014.
25. "A Geological Conservation Strategy for Hertfordshire" (PDF). Hertfordshire RIGS Group. 2003. p. 43. Archived from the original (PDF) on 24 September 2015. Retrieved 4 February 2015.
26. "Frogmore Meadows citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 11 December 2014.
27. "Frogmore Meadow". Herts and Middlesex Wildlife Trust. Archived from the original on 11 December 2014. Retrieved 11 December 2014.
28. "Frogmore Meadows citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 11 December 2014.
29. "Great Hormead Park citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 3 March 2016. Retrieved 19 February 2015.
30. "Hertford Heath". Herts and Middlesex Wildlife Trust. Archived from the original on 11 April 2015. Retrieved 15 February 2015.
31. "Hertford Heath citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 15 February 2015.
32. "Furneux Pelham Gravel Pit (Hillcollins Pit) (Quaternary of the Thames)". Joint Nature Conservation Committee. Archived from the original on 19 February 2015. Retrieved 18 February 2015.
33. "Hillcollins Pit citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 4 March 2016. Retrieved 18 February 2015.
34. "Hunsdon and Eastwick Meads". Herts & Middlesex Wildlife Trust. Archived from the original on 14 September 2016. Retrieved 11 January 2016.
35. "Hunsdon Mead citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 22 December 2014.
36. "Knebworth Woods citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 24 September 2015. Retrieved 3 January 2015.
37. "Little Heath Pit (Quaternary of the Thames)". Joint Nature Conservation Committee. Archived from the original on 18 August 2016. Retrieved 11 January 2016.
38. "Little Heath Pit citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 24 September 2015. Retrieved 25 February 2015.
39. Information board on the site
40. "Moor Hall Meadows citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 24 September 2015. Retrieved 3 January 2015.
41. "Moor Mill Quarry (Quaternary of the Thames)". Joint Nature Conservation Committee. Archived from the original on 4 March 2016. Retrieved 11 January 2016.
42. "Moor Mill Quarry, West citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 24 September 2015. Retrieved 7 December 2014.
43. "Northaw Great Wood Country Park". Local Nature Reserves. Natural England. 14 March 2013. Archived from the original on 10 February 2015. Retrieved 22 March 2015.
44. "Northaw Great Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 3 March 2016. Retrieved 23 December 2014.
45. "Tring Park". English Heritage. Archived from the original on 13 January 2015. Retrieved 23 December 2014.
46. "Oddy Hill and Tring Park citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 4 March 2016. Retrieved 2 June 2016.
47. "Oughtonhead Lane, Hitchin (Quaternary of East Anglia)". Joint Nature Conservation Committee. Archived from the original on 4 March 2016. Retrieved 11 January 2016.
48. "A Geological Conservation Strategy for Hertfordshire" (PDF). Hertfordshire RIGS Group. 2003. Archived from the original (PDF) on 24 September 2015.
49. "Patmore Heath". Herts and Middlesex Wildlife Trust. Archived from the original on 13 December 2014. Retrieved 11 December 2014.
50. "Patmore Heath citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 11 December 2014.
51. "Plashes Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 11 March 2015.
52. "Redwell Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 16 January 2015.
53. "Roughdown Common". Chilterns Conservation Board. Archived from the original on 21 December 2014. Retrieved 21 December 2014.
54. "Roughdown Common citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 21 December 2014.
55. "Rye Meads (SSSI SPA Ramsar)". Royal Society for the Protection of Birds, South East Hertfordshire Local Group. Archived from the original on 29 September 2015. Retrieved 28 September 2015.
56. "Rye Meads". Herts and Middlesex Wildlife Trust. Archived from the original on 17 July 2015. Retrieved 11 December 2014.
57. "Rye Meads". Royal Society for the Protection of Birds. Archived from the original on 26 November 2014. Retrieved 11 December 2014.
58. "Sarratt Bottom citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 24 September 2015. Retrieved 11 December 2014.
59. "Sawbridgeworth Marsh Nature Reserve". Essex Wildlife Trust. Archived from the original on 11 June 2016. Retrieved 28 December 2014.
60. "Sawbridgeworth Marsh citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 3 March 2016. Retrieved 28 December 2014.
61. "Sherrardspark Wood". Local Nature Reserves. Natural England. Archived from the original on 4 March 2016. Retrieved 12 January 2016.
62. "Sherrardspark Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 24 September 2015. Retrieved 2 June 2016.
63. "Tewinbury". Herts and Middlesex Wildlife Trust. Archived from the original on 2 April 2015. Retrieved 22 March 2015.
64. "Tewinbury citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 22 March 2015.
65. "Therfield Heath". Local Nature Reserves. Natural England. Archived from the original on 3 December 2013. Retrieved 26 July 2013.
66. "1010428 - The National Heritage List for England". Archived from the original on 4 November 2013. Retrieved 12 January 2016.
67. "1010431 - The National Heritage List for England". Archived from the original on 4 November 2013. Retrieved 12 January 2016.
68. "Therfield Heath citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 3 March 2016. Retrieved 2 June 2016.
69. "Thorley Wash". Herts and Middlesex Wildlife Trust. Archived from the original on 13 December 2014. Retrieved 11 March 2015.
70. "Thorley Flood Pound citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 11 March 2015.
71. "Tring Reservoirs". Herts and Middlesex Wildlife Trust. Archived from the original on 27 April 2015. Retrieved 19 April 2015.
72. "Tring Reservoirs citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 4 March 2016. Retrieved 3 June 2016.
73. "Tring Woodlands citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 4 March 2016. Retrieved 14 January 2015.
74. "Tring Woodlands citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 4 March 2016. Retrieved 14 January 2015.
75. "Turnford & Cheshunt Pits citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 20 March 2009. Retrieved 3 June 2016.
76. "Wain Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 3 March 2016. Retrieved 13 January 2015.
77. "Water End Swallow Holes citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 3 March 2016. Retrieved 13 January 2015.
78. "Westwood Quarry (Quaternary of the Thames)". Joint Nature Conservation Committee. Archived from the original on 9 August 2016. Retrieved 12 January 2016.
79. "A Geological Conservation Strategy for Hertfordshire" (PDF). Herts RIGS Group. 2003. p. 43. Archived (PDF) from the original on 6 August 2016. Retrieved 9 June 2016.
80. "Whippendell Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 24 October 2012. Retrieved 9 June 2016.
81. "Broxbourne Woods". Countryside Management Service. Archived from the original on 9 March 2016. Retrieved 12 January 2016.
82. "Wormley-Hoddesdonpark Wood North citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 3 March 2016. Retrieved 18 October 2015.
83. "Danemead". Herts and Middlesex Wildlife Trust. Archived from the original on 16 February 2015. Retrieved 19 April 2015.
84. "Broxbourne Woods". Natural England. Archived from the original on 20 October 2017. Retrieved 17 October 2015.
85. "Map of Wormley-Hoddesdonpark Wood South". Sites of Special Scientific Interest. Natural England. Archived from the original on 3 March 2016. Retrieved 10 January 2016.
86. "Wormley-Hoddesdonpark Wood South citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived (PDF) from the original on 4 March 2016. Retrieved 10 January 2016.