First of all, I must recommend the following website, which I have used extensively for identifying many difficult plants - www.naturespot.org.uk.
(All photos taken at OPS.)
There is also a List of Animals for the site, and a List of Insects.
Total number of species (all genuses) reported at OPS = 1194 (374 Plants & Fungi, 419 Insects, 143 Animals/Fish, 257 Birds (inc. escapes)).
Jump to Water Plants Jump to Trees & Shrubs Jump to Shore Plants
Jump to Ferns, Mosses and Algae Jump to Grasses Jump to Fungi Jump to Lichen
Agrimony

Annual Mercury, BRERC record 31/12/86.
Autumn Hawkbit
Beaked Hawk's-beard, BRERC record 4/5/07.
Bee Orchid

Bittersweet (aka Woody Nightshade)

Black Bindweed, BRERC record 4/5/07.
Black Bryony
Black Medick

Black Mustard
Bluebell - drooping heads and flowers on one side, curled flower tips & nice scent (cf. Spanish Bluebell below).

Bramble
Branched Bur-reed

Bristly Oxtongue, BRERC record 16/6/16.
Broad-leaved Dock
Buck's-horn Plantain, BRERC record 2/10/08.
Buddleia
Bulbous Foxtail - identified in WWT survey within 1km (nationally scarce)
Bush Vetch, BRERC record 2/7/2002.
Camomile
Canadian Fleabane – by jetty. Tiny white/yellow flowers

Cat’s Ear
Chicory – in the wildflower meadow next to car park

Cleavers
Charlock, BRERC record 4/5/2007.
Colt's-foot – large leaves, where weather tower used to be. Flowering on waste-ground.

Comfrey
Common Bird’s-foot-trefoil
Common Bistort
Common Broomrape. A parasite of clover.

Common Centaury

Common Chickweed

Common Dandelion
Common Dog-violet (white version in wood by orchard)
Common Eyebright – very pretty small plant, on path of Lagoon 3, at SW end.

Common Field-speedwell

Common Figwort, BRERC record 17/7/2011.
Common Fleabane

Common Hemp-nettle, BRERC record 31/12/1986.
Common Knapweed

Common Mouse-ear
Common Nettle
Common Poppy
Common Ragwort – common yellow plant around the lagoons

Common Sorrel

Common Spotted Orchid - lip divided into three equal lobes and marked with dark pink dashes and broken lines. (Leaves - not shown - spotted.)

Common Vetch

Corn Parsley, BRERC record 2/7/2002.
Cow Parsley
Cowslip

Creeping Buttercup
Creeping Cinquefoil

Creeping Thistle
Crow Garlic
Cuckooflower
Curled Dock
Cut-leaved Cranesbill

Daffodil

Daisy
Dog Rose

Dog Violet (inc. white-flowered)
Dove's-foot Crane's-bill, BRERC record 31/12/1986.
Dyer's Greenweed, BRERC record 31/12/1986.
Early Marsh Orchid

Evening-primrose
Fat Hen
Field Bindweed

Field Scabious

Field Rose

Foxglove
Germander Speedwell
Giant Hogweed – not on site currently
Goat's Beard
Goldilock's Buttercup – in woods
Grape Hyacinth – garden escape on seawall at Shepperdine
Grass Vetchling

Great Burnet
Great Willowherb

Greater Bird's-foot Trefoil, BRERC record 16/6/2016.
Greater Burdock
Greater Knapweed – paints the meadow next to the car park purple in late summer !

Greater Plantain
Greater Sea-spurrey, BRERC record 31/12/1998.
Ground Elder
Ground Ivy
Groundsel
Gypsywort – bank of lake, next to road (where dogs go in lake). Like mint, but with no smell.

Hairy Tare, along seawall.

Hedge Bedstraw

Hedge Bindweed

Hedge Woundwort
Hemlock, BRERC record 17/7/2011.
Hemp Agrimony – Large patches on Lagoon 2

Herb Robert
Hoary Plantain

Hoary Ragwort

Hoary Willowherb - WWT survey, Lagoon 3, 2019
Hogweed
Honeysuckle, BRERC record 13/12/2006.
Horsetail
Ivy
Knotgrass
Lady’s Bedstraw – common on the path round Lagoon 3

Lesser Burdock
Lesser Celandine

Lesser Hawkbit, BRERC record 16/6/2016.
Lesser Sea-spurrey

Lesser Stitchwort, BRERC record 2/7/2002.
Lesser Trefoil, BRERC record 16/6/2016.
Lords-and-Ladies
Lungwort (Pulmonaria)

Many-seeded Goosefoot, BRERC record 31/12/1986.
Marsh Thistle

Marsh Woundwort

Meadow Buttercup
Meadow Thistle – very common (note smooth stems)

Meadow Vetchling

Meadowsweet
Mistletoe
Mugwort
Musk Mallow, usually pink flowers but also this white form.

Narrow-leaved Bird's-foot-trefoil, shore by Lagoon 1, June 2024.

Nipplewort

Opium Poppy – garden escape, Lagoon 2

Oxeye Daisy
Perennial Sow-thistle – on the saltmarsh by the jetty, late summer

Pale Persicaria, BRERC record 31/12/1986.
Perforate St John's-wort – along tarmac’d path to Lagoon 2

Petty Spurge, BRERC record 17/7/2011.
Pineappleweed
Pink Campion

Prickly Sow-thistle
Primrose

Procumbent Pearlwort, BRERC record 17/7/2011.
Purple-loosestrife
Pyramidal Orchid

Ragged Robin
Rapeseed

Red Bartsia – low-lying but distinctive, along the paths round Lagoon 2

Red Clover
Red dead-nettle

Redshank
Ribbed Melilot, BRERC record 2/10/2008.
Ribwort (Plantain)
Rosebay Willowherb
Round-leaved Crane's-bill, BRERC record 17/7/2011.
Round-leaved Mint

Salad Burnet

Scarlet Pimpernel

Scented Mayweed (has hollow center to flowers), BRERC record 31/12/1986.
Scentless Mayweed – Lagoon 3, by the stone pile

Sea Clover - identified in WWT survey within 1km (nationally scarce). At top of the seawall, by Lagoons 1/2.

Sea Radish - along shore, especially by the jetty (inc. white form in June 2025


Sea Arrowgrass
Sea Plantain
Selfheal
Shepperd's-purse, BRERC record 31/12/1986.
Short-fruited Willowherb
Silverweed, BRERC record 16/6/2016.
Slender Thistle
Smooth Cats Ear

Smooth Hawk's-beard

Smooth Sow-thistle, BRERC record 4/5/2007.
Smooth Tare

Snowdrop

Southern Marsh Orchid - rounded side lobes and a small toothlike central lobe; marked with darker dots and dashes. (Leaves - not shown - usually unspotted.)

Spanish Bluebell - upright stem and open tips & no scent (cf. native Bluebell above).

Spear-leaved Orache - along shore, especially by the jetty

Babington's Orache - BRERC record, 31/12/98
Spear Thistle

Spotted Medick – black spots in the centre of clover-like leaves. On Lagoon paths.

Square-stalked St John's-wort, BRERC record 2/7/2002.
Square-stalked Willowherb, BRERC record 16/6/2016.
Sticky Mouse-ear, BRERC record 16/6/2016.
Stinking Iris

Stone Parsley, BRERC record 17/7/2011.
Strawberry Clover, BRERC record 31/12/1998.
Sun Spurge – around the jetty fence

Caper Spurge – a clump by the paddocks near Oldbury village

Sweet Violet (white form) – near orchard.

Swine-cress, BRERC record 31/12/1986.
Tansy

Tall Melilot – common on path of Lagoon 2

Teasel
Traveller’s Joy (aka Old Man’s Beard)

Thrift (or Sea Pink) – a few clumps on the sea-wall by Lagoon 2
Thyme-leaved Speedwell, BRERC record 17/7/2011.
Tufted Vetch

Upright Hedge Parsley
Wall Speedwell, BRERC record 16/6/2016.
Water Mint – Lagoon 2

White Clover
White Melilot

Wild Angelica

Wild Carrot – the white flowerheads have a single purple flower in the middle (cultivated carrots belong to a different subspecies).

Wild Parsnip - Lagoon 2

Wood Anemone

Wood Avens
Wood Dock
Yarrow
Dotted (Yellow) Loosestrife

Water Figwort

Zigzag Clover, BRERC record 31/12/1986.
Bogbean - in shallow pond by visitor centre

Bistort
Bulrush, BRERC record, in ponds, 13/11/2017
Common Duckweed, BRERC record, in ponds, 2/7/2002
Great Reedmace
Hornwort
Fool’s Watercress – in the rhines (or on the banks after the farmer’s dredging !)

Lesser Water-parsnip, BRERC record 2/7/2002.
Water-cress

Hemlock Water-dropwort - the UK's most deadly plant!

Lesser Reedmace/Lesser Bulrush - in shallow pond by visitor centre
Marsh Marigold

Water Crowfoot
Water Starwort
Water-plantain

Yellow Iris
Spiked Water Milfoil
New Zealand Pigmyweed - invasive that takes over ponds, and unfortunately is creating a large mat in the pond by Lagoon 2

Jointed Rush, BRERC record 17/7/2011.
Toad Rush, BRERC record 4/5/2007.
Alder
Apple
Ash
Aspen – shimmers in wind. Tall specimens along main rhine, by entrance. Round, toothed leaves.

Austrian Pine, BRERC record 17/7/2011.
Beech
Bird Cherry

Black Hawthorn – Two trees in hedge between shore and Lagoon 3.

Black Poplar – quite large, heart-shaped leaves. Tall, thin trees.


Box
Buckthorn

Common Whitebeam - identified in WWT survey, 2019.
Cotoneaster (C. franchetti), Franchet's Cotoneaster. Single plant at north end of Lagoon 2 (red-orange berries in Sept). Non-native, garden escape, spread by birds eating the berries. (Note that many Cotoneaster, e.g. C. horizontalis, but NOT this one, cause problems to native plants by spreading and are illegal to plant in wild (i.e. added to Sched 9 of Wildlife & Countryside Act in 2010).)

Crab Apple
Crack Willow – the hedge across Lagoon 1 shows Crack Willow (yellowy branches, green leaves, on left) and White Willow (green branches, darker green and longer leaves with white backs, on right)

Damson (also Bullace recorded in BRERC, 2/7/02)
Dogwood

Eared Willow - identified in WWT survey, 2019.
Elder
Elm – a good specimen is along the bridleway at far end of lake, which runs along the SW side of Lagoon 3. On left of path (over ditch), the first tree in the tall hedge just before path zig-zags.
Field Maple – distinguished from Sycamore by sides of fruit being in a straight line. Large example on far side of main rhine, just down from entrance.

Grey Willow - identified in WWT survey, 2019.
Guelder Rose

Hawthorn
Hazel
Holly - only one, in shore hedge of Lagoon 3.
Hornbeam - 4 specimens in hedge that runs from road along SW side of Lagoon 3.
Horse Chestnut - just one small tree growing through brambles on Lagoon 2.
Lime
Oak (Pendunculate Oak)
Osier (Willow) - identified in WWT survey, 2019.
Pear

Pussy Willow
Rowan

Sallow
Scot’s Pine – all the pine trees on-site are this species.

Sea Buckthorn – the large silvery bush on the seawall of Lagoon 1
Silver Birch
Sloe (aka Blackthorn) – white flowers before leaves appear, early Spring

Small-leaved Elm, BRERC record 17/7/2011.
Spindle – pink fruit in late autumn. Specimen along tarmac’d path to Lagoon 2, near old visitor centre

Sweet Chestnut – the only specimen is on the lawn in front of the Gatehouse/old Visitor Centre
Sycamore
Turkey Oak – nice specimen on right of approach road. Acorns have ‘hairy’ base.

Wayfaring Tree – shrub with red and black berries, Lagoon 2

White Poplar – large specimen at SW end of Lagoon 3. White back to grey leaves.

White Willow – see photo under ‘Crack Willow’, above.
Wild Cherry – heavy fruiting tree by the entrance (flowers in April)

Wild Service Tree. 2 specimens along tarmac’d path to Lagoon 2, and larger one at S end of meadow.


Wych Elm – note the unsymmetrical leaves at the stalk end – this identifies Elms. Nearly all the hedge on the left side of the tarmac’d path from car park to Lagoon 2 contains Wych Elm, especially at the end by the pond.

Yew – there are only three specimens on-site, all on Lagoon 2. Largest at South end, next to path (smallish one on SW side and new, small, one at N end).
Annual Seablite

Biting Stonecrop – at top of seawall by Lagoon 1

Bladder Wrack – commonest black seaweed along the shore
Common Cord Grass – binds soft silt mud together at exposed side of salt-marsh
Marram Grass – Taller, grey-green grass, on the land-side of saltmarsh.
The photo below is of the saltmarsh at Shepperdine, showing the two above grasses (with more commoner grasses on the seawall).

Common Saltmarsh-grass – BRERC record, 31/12/1998
Sea Aster – common succulent plant on saltmarsh with purple and yellow daisy-like flowers (or yellow flowers with no petals)

Sea Club-rush, BRERC record 24/6/2009.
Sas Mayweed, BRERC record 16/6/2016.
Sea Milkwort – on the seawall

Sea Wormwood, silver plant on the seawall by jetty (And BRERC record 24/6/2009).
Spiral Wrack

Common Scurvygrass – succulent plant on saltmarsh with white flowers starting in May.

Rock Samphire, BRERC record 31/12/1986.
Saltmarsh Rush, BRERC record 31/12/1998.
Hartstongue
Blue-green Algae
Hard Shield-fern

I can highly recommend the following website for identifying grasses - www.naturespot.org.uk.
Barren Brome – by jetty.
Cock's-foot – common along Severn Way sea-wall.

Common Bent, BRERC record 2/7/2002.
Common Couch - WWT survey Lagoon 3, 2019.
Common Reed – the reeds in the large beds on Lagoons 2 & 3
Common Soft-brome – common along Severn Way sea-wall.

Compact Rush, BRERC record 24/6/2009.
Creeping Bent, BRERC record 16/6/2016.
Creeping Soft-grass – common along Severn Way sea-wall.

Crested Dog's-tail
False Fox Sedge

False Brome

False Oat-grass, BRERC record 16/6/2016.
Field Wood-rush

Glaucous Sedge, BRERC record 16/6/2016.
Greater Pond-sedge – in pond to south of Lagoon 3.
Grey Sedge (Carex Divulsa), BRERC record 2/7/2002.
Hairy Broome

Hairy Sedge, BRERC record 2/7/2002.
Hard Rush, BRERC record 16/6/2016.
Hard-grass, BRERC record 24/6/2009.
Lesser Pond-sedge

Lesser Quaking Grass, by pond, Lagoon 2, June2024

Long-bracted Sedge - WWT survey Lagoon 3, 2019.
Meadow Barley, BRERC record 24/6/2009.
Meadow Foxtail, BRERC record 24/5/2007.
Pampas-grass – 2 clumps in middle of Lagoon 3.

Pendulous Sedge – one large clump at south end of Lagoon 2.

Perennial Rye-grass – common along Severn Way sea-wall.

Quaking Grass
Red Fescue, BRERC record 16/6/2016.
Reflexed Saltmarsh-grass – common along Severn Way sea-wall.

Rough Meadow-grass, BRERC record 17/7/2011.
Sea Couch - WWT survey Lagoon 3, 2019.
Sharp Rush - WWT survey Lagoon 3, 2019.
Soft-rush, BRERC record 2/7/2002.
Sweet Vernal-grass, BRERC record 16/6/2016.
Sweet-grass, BRERC record 16/6/2016.
Tall Fescue.

Timothy.
Tufted Hair-grass.

Yorkshire-fog – common along Severn Way sea-wall.

Annual Meadow-grass, BRERC record 16/6/2016.
Bay Bolete
Beefsteak Fungus
Candlesnuff Fungus
Common Puffball

Crimson Wax Cap
Dog Vomit Slime Mold
Drab Bonnet
Dung Fungus – orange
Field Mushroom
Honey Fungus
Horse Mushroom
Ivory Waxcap
Jew's Ear
Peppery Roundhead

Rooting Bolete

Rufous Milkcap

Scarlet Elf Cap
Shaggy Inkcap

St. George's Mushroom
Stump Puffball

Stubble Rosegill

Spectacular Rustgill Mushroom – not edible
Sulphur Tuft

Taphrina alni (Alder Tongue)

Taphrina pruni (Pocket Plums)

Turkeytail
Velvet Shank – on stumps in mid-winter
Yellow Brain
Yellow Fieldcap

Willow Bracket

Ash dieback fungus
Dutch Elm Disease Fungus
Earth Tongue – Lagoon 3, Nov 2021

Field Blewit – Lagoon 3, Dec 2021

Evasive Agaric (Crepidotus versutus) – Lagoon 3, Oct 2022
Wood Blewit – Lagoon 3, Oct 2022

Fanfare Of Trumpets (Ramalina fastigiata)

Xanthoria calcicola

No. of species = 374
There is also a List of Animals for the site, and a List of Insects.