Sowing rocket: identify the species and keep soil moist
Identify the rocket species on your seed packet, then use practical sowing and harvest cues suited to its growth habit.
By Marmanda3 min read
Check the botanical name on the packet: “rocket” or “arugula” may mean cultivated Eruca or perennial Diplotaxis tenuifolia. In the UK, the RHS gives an outdoor sowing window for cultivated rocket from April to early September. The perennial species has a different habit and should be grown using advice that names it explicitly.
Which plant does “rocket” mean?
The RHS distinguishes annual cultivated rocket, Eruca vesicaria subsp. sativa, from perennial wild rocket, Diplotaxis tenuifolia. The perennial grows more slowly and has a different leaf shape; its picking season can continue after flowering. Read the botanical name rather than relying on a label such as “wild”, “rocket” or “arugula”.
Common names can point to different plants in different references. The French SNHF sheet calls Diplotaxis erucoides “roquette sauvage” or false rocket; it is not the same as the perennial D. tenuifolia described by the RHS. The French Ephytia/INRAE plant-protection reference can help confirm the species, but it is not a cultivation guide. Check the Latin name before applying dates or spacing from another source.
How should cultivated Eruca be sown?
For UK conditions, the RHS recommends outdoor sowing from April to early September. Sow in a drill no deeper than 1 cm, with rows 15 cm apart, then thin plants to about 15 cm. It says seedlings emerge in a few days and first leaves can be picked in four to six weeks; these are RHS estimates, not guaranteed timings.
The French SNHF sheet gives a related but different Eruca schedule: April to August for harvest from June to November, or September to October for spring harvest. It advises a 1 cm drill, rows 20 cm apart and thinning to 5–10 cm. Those measurements belong to its French method. Use one guide's complete protocol rather than combining row spacing from one with thinning from the other.
Prepare a fine, moist seedbed, cover lightly and water with a gentle rose if the surface begins to dry. The RHS warns that hot conditions can make rocket bolt, so avoid midsummer sowing during hot, dry weather when possible. Keep the crop under observation instead of following a fixed watering schedule.
What changes with perennial Diplotaxis tenuifolia?
Do not automatically apply the RHS Eruca window to D. tenuifolia. The RHS describes it as slower-growing with a different leaf shape, and says picking can continue after flowering. Its general rocket sowing method is not split by species, so treat its depth, spacing and season as guidance written for rocket in general, not as a separate Diplotaxis schedule.
This perennial may remain in place and regrow in later seasons where conditions suit it. It should not be confused with D. erucoides named as false rocket by SNHF.
How can you keep leaves coming?
Pick leaves progressively and note how the plant responds. Rapid bolting may coincide with hot weather or a drying bed, but one observation does not prove a single cause. Record species, variety, sowing date and site so you can compare batches and keep annual and perennial plants distinct in your notes.
If you want both forms, label the rows with the full species name. That small step helps prevent a later sowing, thinning or harvest note from blending the annual crop with a perennial plant that may stay in the bed. The vegetable sowing and planting calendar gives wider seasonal context, and the small-garden guide can help reserve a section of bed.