Diplotaxis muralis

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Diplotaxis muralis, commonly called the annual wall-rocket, is a small flowering plant in the mustard family. It is native to Europe, Asia and North Africa but has naturalized in many temperate regions around the world.

Description
- It is an upright plant usually 15–60 cm tall, with lobed leaves that form a rosette at the base.
- Stems end in dense clusters of yellow flowers (occasionally pale purple) with small oval petals and large anthers.
- The fruit is a slender, podlike silique 2–4 cm long, containing two rows of yellow-brown, oval seeds.

Lifestyle and habitat
- It is mostly an annual, but can live as a perennial in some places.
- It grows best in waste or disturbed ground, such as beside railways and roads, and on old walls (hence the name “wall-rocket”).
- It flowers in spring and summer: May–September in the UK and April–August in China.
- Pollinators include bees and other flying insects; it is sometimes grown as a green manure.

Taxonomy and origin
- The species was described by Augustin Candolle in 1821, based on Linnaeus's earlier name Sisymbrium murale (1753).
- The name muralis means “growing on walls.” There are two subspecies.
- Diplotaxis muralis is similar to Diplotaxis tenuifolia but is generally shorter and less bushy.
- Some studies suggest D. muralis arose from natural hybridization between D. tenuifolia and D. viminea.

Distribution
- Native to temperate Europe, North Africa and western Asia.
- It has become naturalized in many areas, including the UK since 1778 after seeds were carried from a shipwreck. It is commonly found on waste ground, along railways, roads, and similar disturbed sites.