The Crassulaceae or Stonecrop family on the British Isles

A carpet of the alien New Zealand Pigmyweed or Crassula helmsii, which is swamping out everything at Clayhanger near Walsall. (Picture by Mike Poulton)

The Crassulaceae or Stonecrop family looks ornamental most of the year because of its rounded, succulent and evergreen foliage. However, the flowers give it an extra attraction!

I always associated this family with drought loving plants but I learned it has several moisture loving members too!

Several of the genera and species mentioned in Stace are in fact ornamental garden plants and have ‘escaped’ into the wild as often happens! At least one species of Crassula is now a serious weed, originally introduced as an aquatic ornamental for ponds.

Thanks for pictures donated by Mike Poulton of Ecorecord as well as from Wikipedia Commons. If you can’t see a picture, you will see what it looks like by pressing the link below the (common) Name.

The Scientific name usually has a link from the Online Atlas of the British Isles and Irish Flora. A blue background tells you about the habitat where it can be found in B.I. as well as for interesting facts or wildlife use! A pink background means a warning (such as poisonous!) or medicinal use, green for edible, ornamental or other uses.

Contents:

Crassula or Pigmyweeds:
C. tillaea or Mossy Stonecrop
C. aquatica or Pigmyweed
C. helmsii or New Zealand Pigmyweed
C. decumbens or Scilly Pigmyweed
C. pubescens or Jersey Pigmyweed
Umbilicus rupestris or Navelwort
Sempervivum spp or House-leeks
Sempervivum tectorum or House-leek
Sedum spp. , Rhodiola, Hylotelephium or Stonecrops:
Rhodiola rosea ( syn. Sedum rosea) or Roseroot
Hylotelephium telephium or Orpine
Sedum acre or Biting Stonecrop
S. album or White Stonecrop
S. anglicum or English Stonecrop
S. villosum or Hairy Stonecrop
S. forsterianum or Rock Stonecrop and:

Sedum rupestre or Reflexed Stonecrop
S. anacampseros or Love-restoring Stonecrop
S. dasyphyllum or Thick-leaved Stonecrop
S. hispanicum or Spanish Stonecrop
S. nicaeense or Pale Stonecrop

Crassula or Pigmyweeds

A 27 year old Money or Jade plant grown in Gwynned, Wales.

Crassula is a genus of succulent plants containing about 200 accepted species, including the popular jade plant (Crassula ovata). Cultivated varieties originate almost exclusively from species from the Eastern Cape of South Africa.

Stace describes the 5 species found on the B.I. below:

C. tillaea or Mossy Stonecrop

A tiny annual, growing on bare, often compacted, sandy or gravelly ground.

C. aquatica or Pigmy weed (Picture by Cavan Allen & Wesley Knapp, in Wikipedia Commons)
C. aquatica or Pigmyweed

A small, slender annual which is currently known from only one locality. It grows in shallow water or on wet mud exposed by fluctuating water levels at the side of the River Shiel (Westerness), and on damp peaty soil where the riverside vegetation has been disturbed.

New Zealand Pigmyweed in Clayhanger (by M. Poulton)
C. helmsii or New Zealand Pigmyweed

This perennial herb grows submerged in sheltered waters up to 3 metres deep or as an emergent on damp ground. It grows on soft substrates in a variety of habitats, including ponds, lakes, reservoirs, canals and ditches and can tolerate a wide range of water chemistry. It can form dense, virtually pure stands.

This aggressively colonising species was first cultivated in Britain in 1927 and was discovered in the wild in 1956 (Greensted, Essex). Originally found in Australia and New Zealand, it has been introduced around the world. In the United Kingdom, this plant is one of five introduced invasive aquatic plants that were banned from sale from April 2014, the first ban of its kind in the country. It is on the Global Register of Introduced and Invasive Species of eleven countries.

Scilly Pigmyweed found on St Mary, Isles of Scilly (by Len Worthington in Wikipedia)
C. decumbens or Scilly Pigmyweed

An annual neophyte found naturalised in damp, sandy bulbfields and by tracks on St Mary`s (Isles of Scilly), and elsewhere as a casual from wool shoddy.

C. pubescens or Jersey Pigmyweed

A stoloniferous perennial herb with succulent leaves, naturalised in sandy soil at the base of a granite boulder on Jersey (Channel Islands). Reproduction is by rooting of detached leaves; no seed is produced. This neophyte species has been known from the wild in Jersey since 1970.

The exact identity of our plant is uncertain; it may be C. pubescens subsp. radicans.

Umbilicus rupestris or Navelwort at Tapeley Park, Instow, North Devon (by Sannse- Wikipedia)

Umbilicus rupestris or Navelwort

This is an interesting looking plant. Both the name “navelwort” and the scientific name Umbilicus come from the round shape of the leaves, which have a navel-like depression in the center.

It is a perennial herb, growing on walls, in rock crevices and on stony hedge banks, mainly on acidic substrates. In Cornwall it has even been seen growing as an epiphyte on the boughs of large trees.

Medicinal Use:

Navelwort is assumed to be the “Kidneywort” referred to by Nicholas Culpeper in The English Physician.

  • Vulnerary: The plant is sometimes employed to ease pain on scratches by applying the leaf to the skin after removing the lower cuticle.
  • Umbilicus rupestris is used in homeopathic medicine and goes under the name of Cotyledon umbilicus when used by Homeopaths.
Sempervivum globiferum (Wikipedia)

Sempervivum spp or House-leeks

These are interesting and attractive, but mostly introduced succulents for rockeries or pots and shallow pans. None are natives though!

It is a long-lived, evergreen perennial, planted and more or less naturalised on tiled and thatched roofs, old walls, gate pillars and porches, and in churchyards.

House-leeks on a tiled roof! (by Arnoldius in Wikipedia)
Sempervivum tectorum or House-leek

S. tectorum has been grown in gardens since at least 1200 (Harvey, 1981), and was often planted on porches and roofs as a supposed protection against fire, lightning and thunderbolts. It was known in the wild by 1629.

Aeonium cuneatum in its native Tenerife (by Gabriele Kothe-Heinrich in Wikipedia)

Aeonium cuneatum

This is clearly not a native, but can be seen growing on walls in the SW and Scilly Isles.

Aeonium arboreum ‘Atropurpureum’ or Dark Purple Houseleek Tree (by Mike Poulton)

Aeonium arboreum ‘Atropurpureum’ or Dark Purple Houseleek Tree

This is a dramatic looking exotic, splendid for a colourful display!

Sedum spp. , Rhodiola, Hylotelephium or Stonecrops:

There are 23 species of Sedum described in Stace which are split into 6 sections. A few genera of Sedum have been renamed into another genus. Many are grown as ornamental, rockery plants. the most common or/and native ones are:

Roseroot in its habitat (by Alpsdake in Wikipedia)
Rhodiola rosea ( syn. Sedum rosea) or Roseroot

A rhizomatous perennial herb which grows on sea-cliffs and in mountains in rock crevices and on moist rock ledges. Very rarely, in W. Ireland, it occurs on coastal limestone pavement. In montane habitats it usually occupies sites which are at least slightly base-enriched.

Edible Uses:

The leaves and shoots are eaten raw, having a bitter flavor, or cooked like spinach, and are sometimes added to salads.  An extract is sometimes added as a flavoring in vodkas.

Medicinal Uses:

In Russia and Scandinavia, S. rosea has been used for centuries to cope with the cold Siberian climate and stressful life. It is also used to increase physical endurance and resistance to high-altitude sickness, but the scientific evidence for such benefits is weak. The plant has been used in traditional Chinese medicine, where it is called hóng jǐng tiān.

Montage of flowers & fruits from Roseroot (by Alpsdake in Wikipedia)

Other Uses:

It was previously grown as a source of perfume extracted from the roots, and is occasionally recorded as a garden escape.

A much admired garden plant now called: Hylotelephium spectabile or Ice Plant (by M. Poulton)
Hylotelephium telephium or Orpine

Edible Uses:

The very young leaves can be eaten raw, and both the young leaves and firm tubers can be cooked.

Medicinal Uses and Folklore:

The plant has been used medicinally, being used by the Romans to treat wounds, and in later times to treat internal ulcers. It has also been used for love-divination. As the stems and leaves can store water, when picked. Hence common name livelong. They were hung in a room, where a girl was to be married to a boy. If the stems grew together, this ‘sign’ would mean that the marriage would be blessed and she would be happy. Alternatively, if they grew apart, the marriage prospects looked bad and if a stem died, this would portent death.

Ornamental Uses:

The flowers are held in dense heads and can be reddish or yellowish-white. A number of cultivars, often with purplish leaves, are grown in gardens as well as hybrids between this species and the related Hylotelephium spectabile (iceplant)

Starry Stonecrop (by M. Poulton)
Phedimus stellatus or Starry Stonecrop

This annual species is now naturalised in Somerset. See for more information on the links provided.

Biting Stonecrop (by M. Poulton)
Sedum acre or Biting Stonecrop

A perennial herb of dry, undisturbed and open habitats on skeletal, or virtually non-existent, acidic or basic soils. Typical natural habitats include shingle, sand dunes, cliffs and steeply sloping, S.-facing rocks. It is also frequent on walls, roofs, gravel tracks, pavements and road verges. 

Ornamental uses:

Biting stonecrop spreads when allowed to do so, but is easily controlled, being shallow-rooted. It is used in hanging baskets and container gardens, as a trailing accent, in borders, or as groundcover. This plant grows as a creeping ground cover, often in dry sandy soil, and is a useful component on roof gardens.

The leaves contain an acrid fluid that can cause skin rashes.

White Stonecrop (Pictures by M. Poulton)
S. album or White Stonecrop

This creeping perennial herb grows on open, dry sites, such as limestone rocks, walls, roofs, the concrete of old airfield runways, maritime shingle, paths and gravel on graves. It is treated here as an alien, though some authors have suggested that it may possibly occur as a native on limestone rocks at the eastern end of the Mendips and in S. Devon.

Sedum album is able to acclimate to its environment. It can switch between C3 carbon fixation and crassulacean acid metabolism (CAM) depending on the availability of water. CAM saves water as the stomata on its leaves only open to allow CO2 to diffuse into the leaves at night when the temperature (and therefore evapotranspiration) is lower. Drought stressed plants are also more susceptible to photoinhibition which CAM may help to protect against.

English Stonecrop on a Dutch Dyke around Marken!
S. anglicum or English Stonecrop

This creeping perennial herb of base-poor substrates occurs on rocks, dunes and shingle, and is also known from dry grassland. It is a characteristic plant of open ground on acidic rock outcrops near the sea. It also grows on old walls, rocky hedge banks, and quarries and mine spoil on acidic substrates.

S. villosum or Hairy Stonecrop

A small biennial or perennial herb which grows in at least slightly base-enriched, wet, stony ground and on streamsides in hilly areas, and in montane, often bryophyte-rich, flushes.

S. forsterianum or Rock Stonecrop

A mat-forming perennial herb of open, dry, well-drained habitats, including rocks and screes, wooded cliffs and gullies. Naturalised colonies are found in churchyards, on waste ground, mine waste, walls and railway land.

Several other species have been mentioned in the Online Atlas which are mostly attractive introduced species from gardens and a link is provided to learn more.

S. dasyphyllum or Thick-leaved Stonecrop (by M. Poulton)

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