Variation
There are many variations of Raphanus sativus that include white, red or black tubers that are long, broad or rounded.  Please contact your local nursery for a available varieties that are suitable for your region.

var. longipinnatus 
Daikon, White Radish, Japanese Radish, Oriental Radish, Mooli
This tuberous perennial as large erect dark green lobed leaves and produces a creamy white tuberous root that is up to 350 mm (14 in) long by 100 mm (4 in) in diameter and tapers towards the base. 

There are several varieties available such as the turnip-shaped sakurajiama daikon that grows to 500 mm (20 in) in diameter and weighs up to 45 kg (100 lb). In the southern England a variety known as 'Long White Icicle' produces a root that is similar to a parsnip during midsummer and the Chinese radish or Mooli variety tolerates higher temperatures than the Japanese variety.  

All require an open sunny position and grow in fertile moist but well-drained soils.
The mature roots can be lifted and stored for several weeks in a cool dry place and if left in the ground they become hard and woody.

var. oleiformis
Fodder Radish
This summer annual has tuberous roots and grows to 200 mm (7¾ in) tall and wide with dark green aromatic deeply lobed (almost leaflets) lacerate leaves that have serrated margins and the pale purple to pink rotate flowers appear in a raceme above the foliage during summer. 

Both the leaves and the tubers can be eaten or oil can be extracted from. It prefers an open sunny wind protected position and it grows in well-drained fertile moist sandy to clay loam which is acidic tending the neutral with a pH range from 5.6 to 7.5.