Arabis or rockcress, is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of flowering plant

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

s, within the family Brassicaceae

Brassicaceae

Brassicaceae, a medium sized and economically important family of flowering plants , are informally known as the mustards, mustard flowers, the crucifers or the cabbage family....

, subfamily Brassicoideae.

Though traditionally recognized as a large genus with many Old World

Old World

The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....

 and New World

New World

The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...

 members, more recent evaluations of the relationships among these species using genetic data suggest that there are two major groups within the old genus Arabis. These two groups are not each others closest relatives, so have been split into two separate genera. The Old World members all remain in the genus Arabis, whereas most of the New World members have been moved into the genus Boechera

Boechera

Boechera is a genus of the family Brassicaceae. It was named after the Danish botanist Tyge W. Böcher , who was known for his research in alpine plants, including the mustards Draba and Boechera holboellii...

, with only a few remaining in Arabis.

The species are herbaceous

Herbaceous

A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...

 annual

Annual plant

An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...

 or perennial plant

Perennial plant

A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...

s, growing to 10-80 cm tall, usually densely hairy, with simple entire to lobed leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 1-6 cm long, and small white four-petalled flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s. The fruit

Fruit

In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

 is a long, slender capsule

Capsule (fruit)

In botany a capsule is a type of simple, dry fruit produced by many species of flowering plants. A capsule is a structure composed of two or more carpels that in most cases is dehiscent, i.e. at maturity, it splits apart to release the seeds within. A few capsules are indehiscent, for example...

 containing 10-20 or more seed

Seed

A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s.

Some species, notably A. alpina, are cultivated as ornamental plant

Ornamental plant

Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

s in garden

Garden

A garden is a planned space, usually outdoors, set aside for the display, cultivation, and enjoyment of plants and other forms of nature. The garden can incorporate both natural and man-made materials. The most common form today is known as a residential garden, but the term garden has...

s. Many others are regarded as weed

Weed

A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

s.

Some species are rare, such as Arabis fecunda, which is endemic to Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

 and known from only 19 occurrences.

Selected species

• Arabis aculeolata
  Arabis aculeolata
  Arabis aculeolata is a species of flowering plant in the mustard family known by the common name Waldo rockcress. It is native to a small range in the mountains of southern Oregon and northern California, where it is an uncommon member of the serpentine soils flora...
  
  
• Arabis alaschanica
• Arabis alpina
  Arabis alpina
  Arabis alpina is a flowering plant in the family Brassicaceae that grows in mountainous areas of Europe, north Africa, central and eastern Asia and parts of North America. In the British Isles, it is only known to occur in a few locations in the Cuillin Ridge of the Isle of Skye.The stems of A...
  
  (Alpine Rockcress)
• Arabis amplexicaulis
• Arabis arendsii
• Arabis auriculata
• Arabis axilliflora
• Arabis bijuga
• Arabis blepharophylla
  Arabis blepharophylla
  Arabis blepharophylla is a species of rock cress known by the common names Coast rock cress and Rose rock cress. It is endemic to California, growing mostly in the San Francisco Bay Area and nearby low-elevation California Coast Ranges....
  
  (Coast Rockcress)
• Arabis brownii (Fringed Rockcress; syn. A. hirsuta var. brownii)
• Arabis dispar
• Arabis fecunda (Sapphire rockcress)
• Arabis ferdinandi-coburgii
• Arabis glabra
  Arabis glabra
  Arabis glabra, or tower mustard, is a tall, slim, grey-green plant with small creamy flowers at the top of the stem. It usually grows on poor chalky or sandy soils, in open situations. It is native to Europe, Asia, and North Africa, and it is widespread in North America where it is also probably...
  
  (Tower Mustard)
• Arabis hirsuta
  Arabis hirsuta
  Arabis hirsuta is a flowering plant of the genus Arabis in the family Brassicaceae. It is native to Europe, Asia, and the northern half of North America.-External links:****...
  
  (Hairy Rockcress)
• Arabis hoffmanii
• Arabis holboellii
  Boechera holboellii
  Boechera holboellii or Holbøll's Rockcress is found in Greenland. Its cytology has been much studied by the Danish botanist Tyge W. Böcher...
  
  
• Arabis inyoensis
• Arabis johnstonii
• Arabis kennedyae
  Arabis kennedyae
  Arabis kennedyae, the Troodos Rockcress, is a species of flowering plant in the Brassicaceae family.It is endemic to Cyprus.Its natural habitat is Mediterranean-type shrubby vegetation.It is threatened by habitat loss.-Source:...
  
  

• Arabis kokonica
• Arabis lemmonii
  Arabis lemmonii
  Arabis lemmonii is a species of flowering plant in the mustard family known by the common name Lemmon's rockcress. It is native to western North America from Alaska to California to Colorado, where it grows in a number of rocky habitat types. This is a perennial herb growing many small stems from a...
  
  
• Arabis lyallii
• Arabis macdonaldiana
  Arabis macdonaldiana
  Arabis macdonaldiana is a species of flowering plant in the mustard family known by the common name MacDonald's rockcress. It is native to northern California and Oregon, where it grows on newly exposed, barren serpentine soils in openings in temperate coniferous forest habitat...
  
  
• Arabis modesta
• Arabis paniculata
• Arabis parishii
• Arabis pauciflora
• Arabis pendula

• Arabis perstellata
  Arabis perstellata
  Arabis perstellata is a rare species of flowering plant in the mustard family known by the common names Braun's rockcress and Nevada rockcress. It is native to Kentucky and Tennessee, where it is known from perhaps 25 total populations. Most of the occurrences have few individuals, and all are...
  
  
• Arabis pinzliae
• Arabis planisiliqua
• Arabis platysperma
• Arabis procurrens
• Arabis pterosperma
• Arabis puberula
• Arabis pulchra
• Arabis pygmaea
• Arabis recta (Annual Rockcress)
• Arabis repanda
• Arabis rollei
• Arabis scabra (Bristol Rockcress)
• Arabis serotina
  Arabis serotina
  Arabis serotina is a rare species of flowering plant in the mustard family known by the common name shale barren rockcress. It is native to eastern West Virginia and western Virginia in and around the Shenandoah Valley, where it is known from fewer than 60 populations...
  
  
• Arabis serrata
• Arabis shockleyi
• Arabis subpinnatifida
• Arabis suffrutescens
• Arabis tibetica
• Arabis tiehmii
• Arabis tricornuta
• Arabis turrita (Tower Rockcress)