Crassula helmsii

Crassula helmsii
File:Crassula helmsii.jpg
shrubs and flowers of C. helmsii
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Saxifragales
Family:	Crassulaceae
Genus:	Crassula
Species:	C. helmsii
Binomial name
Crassula helmsii (Kirk) Cockayne
Synonyms
Tillaea recurva Tillaea helmsii Crassula recurva

Crassula helmsii, known as swamp stonecrop or New Zealand pigmyweed, is an aquatic or semiterrestrial species of succulent plant in the family Crassulaceae. 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 aquatic plants which were banned from sale from April 2014. This is the first ban of its kind in the country.

Description

The shoots are rather stiff, carrying narrow parallel-sided leaves in opposite pairs, each leaf being about 4–24 millimetres (0.16–0.94 in). Small white flowers with four petals are produced in summer on long stalks arising from the upper leaf axils. The flowers are always above water.

Ecological aspects

The plant grows on the muddy margins of ponds where it forms carpets with 100% cover, or semi-submerged in deeper water, or totally submerged with elongated stems. It does not die back in winter.

Cultivation

C. helmsii is able to grow fully submerged in a cool water aquarium or as a submersed or marginal plant in a pond. Once established it can grow vigorously and may need to be trimmed back. Schedule 9 of the UK Wildlife and Countryside Act 1981 lists this plant as one that cannot be caused to grow in the wild.

External links

• BioImages
• Status in N. Ireland includes an introduction on UK information
• Flora of N. Ireland - illustrated
• Close up of flower
• Ecological information

• http://www.bbc.co.uk/news/science-environment-21232108
• Crassula helmsii :: Invasive Aliens in Northern Ireland