Rocket

Rocket (Eruca sativa), better known to many gardeners as arugula, is a fast-growing annual leafy green in the mustard and cabbage family, Brassicaceae, grown as a cool-season salad and cooking crop.134 It is native to the Mediterranean and parts of Asia, with a range that takes in southern Europe, North Africa, the Middle East, Iran, India, and Pakistan, where it has long been raised as a winter crop in dry areas.134 For a homesteader the appeal is speed and simplicity: sown directly into open ground, it goes from seed to a peppery cutting green in a matter of weeks, fits neatly into the shoulder seasons, and even crops on a bright windowsill in winter.15

The plant begins as a fast-growing rosette from seed, much like a radish or a lettuce.14 Its leaves form a low basal rosette and are deeply pinnately lobed, with a larger terminal lobe that gives them a look somewhere between a dandelion and a mustard; the texture is tender but firmer than lettuce, and the flavour is peppery and mustard-like, with a nutty, horseradish edge described in horticultural taste notes.13 As the plant matures and bolts, it throws up erect, branched flowering stems from the rosette.14 The flowers are the typical four-petalled brassica type, carried in terminal racemes; they are commonly pale creamy white to yellowish with darker veins, though some descriptions note bright yellow flowers, reflecting differences between varieties.23 These are followed by slender seed pods, or siliques, holding small brown seeds used for oil and condiments in parts of the Middle East and South Asia.234 The USDA distinguishes true garden rocket or arugula (Eruca sativa) from the perennial “wild rocket” (Diplotaxis tenuifolia): Eruca sativa is the annual with broader, softer leaves, while Diplotaxis is perennial with narrower, tougher foliage.7

Growing rocket

Rocket is propagated almost exclusively by seed, and it is one of the easiest crops to direct-sow.15 Sow shallowly outdoors as early as the soil can be worked in spring; Fine Gardening recommends about a quarter of an inch deep into well-worked, moisture-retentive soil.15 Because it is a true cool-season crop, grown much like lettuce or spinach, it tolerates frost and can go in the ground several weeks before the last spring frost.1 In hot conditions it bolts quickly and turns to flower, so siting it in partial shade can stretch the harvest in warm climates.15 In its native range it is traditionally grown as a winter crop in dry areas, and in milder-winter regions it works well as a winter or shoulder-season green.14

For a steady supply rather than one glut, make successive sowings every two to three weeks from early spring through to fall.1 Letting a few plants run to flower and set seed can give self-sown fall crops in suitable climates, so the patch effectively reseeds itself.1 Rocket also grows well in containers, including indoors on a bright winter windowsill.1 Because it is grown as a quick annual vegetable, its success depends far more on catching cool weather than on surviving any particular winter; the general sources here do not assign it a strict hardiness zone.145

Harvest and uses

Rocket is harvested young as a leafy green, cut from the rosette before the plant bolts and the leaves turn sharp; treating it like lettuce or spinach and taking leaves over a cool stretch is the simplest approach.1 The leaves are eaten as a peppery, mustard-flavoured salad and cooking green, valued for the nutty, horseradish bite that defines the crop.13 Beyond the leaf, the seeds are pressed for oil and made into condiments in parts of the Middle East and South Asia, where the plant has long been grown for this purpose.24 Leaving some plants to flower and set seed therefore yields a second product as well as the next season’s sowing stock.12

Chemically, rocket sits firmly within the mustard family, and its peppery flavour comes from the glucosinolate compounds characteristic of the Brassicaceae, which have been the subject of food-chemistry and nutritional research on the crop.4 As a homestead vegetable it is best understood as a fast, low-effort cutting green that delivers fresh leaves far quicker than most crops, with an edible seed as a bonus where the season allows it to mature.14

How to identify it

Rocket can be recognised by the following combination of features:1234

• Habit: A fast-growing annual that starts as a low basal rosette, similar to a radish or lettuce, then sends up erect, branched flowering stems as it bolts.
• Leaves: Deeply pinnately lobed with a larger terminal lobe, giving a dandelion-meets-mustard outline; tender but firmer than lettuce, with a peppery, nutty, horseradish-like taste.
• Flowers: Four-petalled brassica flowers in terminal racemes, pale creamy white to yellowish with darker veins (and bright yellow in some varieties).
• Seeds: Held in slender pods (siliques); small and brown.
• Look-alike: Not to be confused with perennial wild rocket (Diplotaxis tenuifolia), which has narrower, tougher leaves.7

Sources

1. Arugula (Eruca sativa) — University of Wisconsin-Madison Division of Extension
2. Rocket (Eruca sativa Mill.) plant portrait — NordGen
3. Eruca sativa — Wikipedia
4. Eruca sativa review — PMC (National Library of Medicine)
5. Arugula or rocket: a favorite salad green — Fine Gardening
6. Eruca sativa study — Notulae Botanicae Horti Agrobotanici
7. Eruca sativa taxon record — USDA APHIS