Sisymbrium irio
London rocket
Mediterranean, North Africa, and southwestern Asia
SunFull Sun – Part Shade
Overview
Sisymbrium irio is a winter annual herb in the mustard family growing 12-24 inches (30-60 cm) tall on slender, branched, mostly smooth stems. The lower leaves are deeply lobed, 2-4 inches (5-10 cm) long, with a large terminal lobe and several smaller side lobes, while upper leaves are narrower. Small four-petaled yellow flowers about 0.1-0.2 inch (3-4 mm) across cluster at the stem tips and open in succession as the stalk lengthens. Each flower forms a slender, upward-curving seedpod (silique) 1-1.5 inches (2.5-4 cm) long holding many tiny seeds; flowers and ripening pods often appear on the same stalk. S. irio germinates with cool fall and winter rains, grows fast through winter and early spring, and dies as heat arrives. It grows readily in disturbed ground, gardens, roadsides, and desert washes, forming dense stands after wet winters that crowd out slower seedlings. The plant self-seeds heavily and reappears year after year, a drawback in cultivated beds. Young leaves carry a peppery, mustard taste.
Native Range
Sisymbrium irio is native to the Mediterranean region, North Africa, and southwestern Asia. It has naturalized across the southwestern United States, especially the Sonoran Desert, and in temperate and arid regions worldwide.Suggested Uses
Sisymbrium irio is rarely planted and is usually treated as a weed of gardens, fields, and desert roadsides. Young leaves and shoots are edible with a peppery flavor and have a history of use as a cooked or raw green. It occasionally appears in wild-food foraging and traditional herbal use.How to Identify
Appearance
Size & Dimensions
Height1' - 2'
Width/Spread6" - 1'
Bloom Information
Yellow flowers open from late winter into spring, roughly January to April, soon after winter rains. Bloom continues for several weeks as the stalk lengthens and pods form below. The plant sets abundant seed before drying off with the first heat of late spring.
Detailed Descriptions
Foliage Description
greenGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Water & Climate
Water Needs
Drought Tolerance
Drought tolerant when established
Care & Maintenance
Care Guide
Sisymbrium irio grows in full sun to light shade and in almost any soil, from sand to clay, as long as it is not waterlogged. It survives on winter rainfall alone and needs no irrigation or feeding. Seed sprouts in cool, moist soil in fall and winter, and the plant completes its cycle in a few months. In gardens it spreads quickly by self-sown seed and can blanket open ground. Pulling or hoeing seedlings before they flower reduces the seed bank. The plant has few serious pests and dies back naturally as temperatures rise.Pruning
No pruning is required. Cutting or pulling plants before the pods ripen prevents most reseeding. Removing dried stems after seed drop keeps beds tidy but does little to reduce next-season germination once seed has fallen.✓ Toxicity
Non-toxicPlanting Guide
Planting Methods & Timing
Planting Method
direct sow
Direct Sow Timing
fall
Days to Maturity
60–120 days
Plant Spacing
8 inches