Sweet rocket

Sun

Full sun to partial shade; light afternoon shade helps in warmer areas.

Water

Moderate; water during establishment and prolonged dry spells, allowing the surface soil to dry slightly between waterings.

Soil

Moist but well-drained soil, preferably reasonably fertile; tolerates clay, loam and chalk if drainage is adequate.

Height

2-3 ft (0.6-0.9 m)

Spread

1-2 ft (0.3-0.6 m)

Flowers

Late spring to early summer; purple, lilac, pink or white, with four petals per flower.

Foliage

Roughly hairy, toothed, lance-shaped green leaves arranged alternately on the stems; basal rosettes may remain green through mild winters.

Growth

Fast; usually forms a leafy rosette in its first year and flowers in its second.

Care needed

Medium

• Pollinators
• Cold hardy
• Low allergen
• Fragrant

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.7 ft (0.53 m)

3. After 2 years

   2.5 ft (0.75 m)

   full size

About 2 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Invasive in

the US and Canada

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Check local invasive-plant rules before buying or sowing it.
• Space plants 1-1.5 ft (0.3-0.45 m) apart for airflow.
• Water young plants regularly until established, then during extended dry weather.
• Apply a thin layer of compost in spring; avoid heavy nitrogen feeding, which encourages floppy growth.
• Stake tall stems early in exposed positions.
• Remove unwanted seedlings promptly, including those outside the planted bed.

Pruning. Cut flowering stems down to the basal leaves as blooms fade, before seed pods mature. Remove dead stems and unhealthy foliage in autumn; do not leave cut seed-bearing stems on the ground.

Early spring

Remove unwanted seedlings and check overwintered rosettes for slug damage.

Spring

Plant nursery-grown rosettes where cultivation is permitted; water well and add a thin compost mulch.

Late spring

Support tall stems in windy sites and water if the soil becomes dry.

Early summer

Deadhead promptly before seed pods develop.

Late summer

Where cultivation is permitted, sow seed in pots for replacement plants; most will flower the following year.

Autumn

Remove spent stems and surplus rosettes, keeping the planting within its intended area.

• Use small groups through the middle of a cottage border with foxgloves and hardy geraniums for an informal late-spring display.
• Place near an evening seating area or path to enjoy the fragrance.
• Combine white-flowered plants with white alliums and silver foliage in a moon garden.
• Use at a lightly shaded woodland edge with columbines, only where it is not invasive and seedlings can be controlled.

Garden styles it suits: Cottage garden, English country, Romantic rose garden, Sensory garden, Moon garden and Blues and silvers.

Plant it with: Foxglove, Columbine, Hardy geranium, Allium, Lady's mantle and Catmint.

Wildlife: Flowers provide nectar for butterflies, moths and bees. In invaded habitats, dense stands can displace native plants, so its value to visiting insects does not justify planting it where it is invasive.

• Unwanted self-seeding: cut off flower stems before pods mature and pull seedlings while small.
• Slugs and snails damage young rosettes: inspect after dark, hand-pick and use barriers or an approved iron-based bait where needed.
• Powdery mildew causes white patches on leaves: improve spacing, avoid drought stress and remove badly affected foliage.
• Clubroot causes swollen roots, wilting and poor growth: remove affected plants, avoid moving contaminated soil and do not replant cabbage-family plants in that spot.

Not known to be toxic to people, cats, dogs or horses, but reliable species-specific animal safety information is limited. Do not deliberately feed any part to pets or livestock; this is an ornamental planting, not a recommended food plant.

Where it spreads. Spreads aggressively by seed in much of northern and central North America, including the northeastern and midwestern United States, parts of the Pacific Northwest, southern Ontario and southern Quebec. It is listed or regulated in several US states, including Colorado and Wisconsin. Avoid planting near woodland, streambanks or natural areas, and check state, provincial and local restrictions.

• Garden phlox (Phlox paniculata)

  Garden phlox has five petals and opposite leaves; sweet rocket has four petals and alternate leaves.

• Annual honesty (Lunaria annua)

  Honesty has broader, often heart-shaped leaves and flat, round, papery seed pods; sweet rocket has narrower leaves and long, slender pods.

• Virginia stock (Malcolmia maritima)

  Virginia stock is a much shorter annual with a low, branching habit; sweet rocket makes tall, upright flowering stems above a basal rosette.

Hesperis comes from the Greek word for evening, referring to the evening fragrance, while matronalis means 'of a matron' and is reflected in the name dame's rocket.

Propagation. Where cultivation is permitted, sow seed in spring or late summer in pots or a prepared seedbed, covering it lightly. Transplant young rosettes before their roots become crowded; flowering usually follows in the second year. Do not distribute seed where the plant is invasive or restricted.

Accepted botanical name

Hesperis matronalis

In the US and Canada

Introduced in Alaska, Canada and the lower 48 states.

Native range

Albania, Austria, Bulgaria, Czechoslovakia, France, Greece, Hungary, Italy, Krym, North Caucasus, Poland and Romania.

Measured

Soil pH 5 to 7. Average height 83 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.