Greater sea kale
Crambe cordifolia ·
A cloud of tiny, honey-scented white flowers, as wide as a doorway, hovers in early summer over a heap of huge, dark, crinkled leaves.
- Size
- 6 ft tall, 5 ft wide
- Zones
- 5 to 8
- Light
- Full sun
- Flowers
- Early June to early July
- Pets
- Not checked
- Job in a bed
- Specimen
A bed built around greater sea kale
The planner designed this bed around greater sea kale when this page was made: a 16 × 8 ft (4.9 × 2.4 m) English border in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why greater sea kale stands where it does.
The plants
- 1 Greater sea kale × 1, white
- 2 Verbena 'Homestead Purple' × 5, purple
- 3 Blue moor grass × 11, purple
- 4 Southernwood × 3, grey-green leaves
- 5 Switchgrass 'Prairie Sky' × 4, tan
- 6 Eastern bee balm × 3, pink
- 7 Black-eyed Susan × 3, yellow
- 8 Persian fritillary × 4, purple
- 9 Easter lily × 5, white
- 10 Grape hyacinth × 3, blue
Why this plant
- The only bold leaves here. The rest are medium and fine. A change of leaf keeps plants distinct when nothing is in flower.
Why here
- Anchors a back corner. At 6 ft it is the tallest plant here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to switchgrass 'Prairie Sky' (5 ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A feature plant is seen as an object, and needs clear ground around it.
Why now
- In flower for five weeks. From early June to early July.
- In company. With verbena 'Homestead Purple' and eastern bee balm in early June: 3 kinds at once.
Planned as an English border: 6 of the 8 groups (75%) are drifts, longer along the bed than they are deep. The scheme leans cool (purple, pink and blue) and uses yellow for warmth, with white and tan to calm things between them. Purple is the colour seen most, on 3 of the 9 kinds grown for their flowers.
The planner's own design check: 8 Excellent, 8 Good, 1 Satisfactory.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where greater sea kale goes in a border
At 6 ft it belongs at the back of a bed. In the planner's ten height classes it is very tall (5 to 6½ ft). It is airy enough to see through, so it can also come forward and veil what is behind it.
Its job: specimen. A feature plant with a shape of its own. It stands alone with room around it, and repeats only at a distance.
It is baby's breath on a giant scale. Give it a deep, well-drained soil and room: the leaves need a square metre. They die back by late summer, so plant something late in front.
- A dramatic cloud of white in June
- Large borders
- Partnering with old roses
What to plant with greater sea kale
Plants recorded as good partners for it, and what each pairing does:
- English rose: in flower together for five weeks, from early June; medium leaves against its bold ones.
- Delphinium: in flower together for three weeks, from late June; medium leaves against its bold ones.
- Catmint 'Six Hills Giant': in flower together for five weeks, from early June; fine leaves against its bold ones; low enough (3 ft) to stand in front of it.
Questions about greater sea kale
Does greater sea kale need sun or shade?
Greater sea kale grows in full sun (6 or more hours of direct sun a day).
It wants ordinary well-drained soil, of average fertility, and little watering once settled.
What zones does greater sea kale grow in?
USDA zones 5 to 8. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Above zone 8 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does greater sea kale flower in my zone?
In zone 5 it flowers early June to early July. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 5 | Early June to early July |
|---|---|
| Zone 6 | Early June to early July |
| Zone 7 | Late May to late June |
| Zone 8 | Late May to late June |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should greater sea kale be planted?
4 ft (120 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 5 ft (150 cm), so a group knits into one patch.
It grows 6 ft (180 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many greater sea kale plants do I need?
Usually one. At 4 ft (120 cm) across, it is a plant you place, not one you mass. For a hedge or screen, set them 4 ft apart: three plants for a 10 ft run.
In the bed above, the planner used one in one group.
Is there a native plant like greater sea kale?
Greater sea kale is not native to North America. These North American natives come closest to doing its job:
- Goat's beard: the same job in a bed and the same flowering time; 12 in shorter, 8 in narrower.
- White false indigo: the same job in a bed, the same flowering time and the same colour; 24 in shorter, 12 in narrower.
- Hardy hibiscus: the same job in a bed and the same colour; 12 in shorter, 12 in narrower.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
What flowers after greater sea kale?
Greater sea kale is over by early July. These start as it finishes and carry the same spot on, so it never goes flat:
- Hardy hibiscus: from late July to mid September, 5 ft tall.
- Russian sage: from mid July to mid September, 4 ft tall, to stand in front of it and cover its fading stems.
- Tiger lily: from late July to late August, 4 ft tall, to stand in front of it and cover its fading stems.
What does greater sea kale look like in winter?
Greater sea kale dies down to the ground and there is nothing to see until spring. The old stems can be cut in autumn, or left until spring as shelter for overwintering insects.
More Crambe
- Sea kale Crambe maritima
In these guides
Every fact on record
- Type
- Perennial
- Size
- 6 ft (180 cm) tall, 5 ft (150 cm) wide
- Plant
- 4 ft (120 cm) apart
- Height class
- Very tall (5 to 6½ ft)
- Place in the bed
- Back, or further forward: it is airy enough to see through
- Flowers
- Early June to early July; airy sprays; white
- Leaves
- Bold texture, herbaceous; dark green
- Shape
- Upright, clumping
- Hardy in
- USDA zones 5 to 8
- Light
- Full sun
- Soil
- Average, well-drained
- Water
- Low
- Feeding
- Light, in spring
Not yet checked against an outside reference: its figures rest on general horticultural knowledge. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.