Ornamental rhubarb
Rheum palmatum 'Atrosanguineum' · Polygonaceae
Leaves a metre across, jagged like a giant maple's, that unfurl crimson-purple from scarlet buds; then a towering plume of cherry-red flowers.
- Size
- 6 ft tall, 5 ft wide
- Zones
- 5 to 7
- Light
- Full sun to part sun
- Flowers
- Late May to late June
- Pets
- Toxic (moderate)
- Job in a bed
- Specimen
A bed built around ornamental rhubarb
The planner designed this bed around ornamental rhubarb 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 ornamental rhubarb stands where it does.
The plants
- 1 Ornamental rhubarb × 1, red
- 2 Mouse-ear coreopsis 'Nana' × 40, yellow
- 3 Winter heath × 8, pink
- 4 White mugwort × 3, cream
- 5 False sunflower 'Summer Sun' × 5, yellow
- 6 Little bluestem × 3, blue-green leaves
- 7 Turtlehead 'Hot Lips' × 3, pink
- 8 Ornamental onion 'Purple Sensation' × 5, purple
- 9 Easter lily × 4, white
- 10 Hardy gladiolus × 5, pink
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.
- The only red.
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 false sunflower 'Summer Sun' (3½ 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 late May to late June.
- Fills a gap. For one of those weeks nothing else on the plan is in flower.
Planned as an English border: 7 of the 7 groups (100%) are drifts, longer along the bed than they are deep. The most in flower at one time is 4 kinds, from late May. The bed is tied together by its repeats: two kinds come round again along it, mouse-ear coreopsis 'Nana' and winter heath.
The planner's own design check: 8 Excellent, 7 Good, 2 Satisfactory.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where ornamental rhubarb 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).
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.
The grandest foliage plant for a cool, moist garden. The spring unfurling is the best moment. It needs deep, rich soil, and collapses in hot summers.
- A bold foliage centrepiece
- Pond sides and moist borders
- Spring drama
What to plant with ornamental rhubarb
Plants recorded as good partners for it, and what each pairing does:
- Siberian iris: in flower together for four weeks, from late May; fine leaves against its bold ones; low enough (2½ ft) to stand in front of it.
- Japanese iris: in flower together for two weeks, from late June; medium leaves against its bold ones; low enough (3 ft) to stand in front of it.
- Globeflower: in flower together for four weeks, from late May; medium leaves against its bold ones; low enough (2½ ft) to stand in front of it.
Questions about ornamental rhubarb
Does ornamental rhubarb need sun or shade?
Ornamental rhubarb grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).
It wants soil that stays evenly moist, rich in organic matter, and plenty of water.
What zones does ornamental rhubarb grow in?
USDA zones 5 to 7. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Above zone 7 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 ornamental rhubarb flower in my zone?
In zone 5 it flowers late May to late June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 5 | Late May to late June |
|---|---|
| Zone 6 | Late May to late June |
| Zone 7 | Mid 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 ornamental rhubarb 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 ornamental rhubarb 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 ornamental rhubarb poisonous to dogs and cats?
Yes: moderate toxicity to people, dogs, cats and horses. The leaves contain oxalic acid and are poisonous if eaten.
Rated from the ASPCA. Where references disagree, the more cautious rating is used.
Is there a pet-safe plant like ornamental rhubarb?
These come closest to doing what ornamental rhubarb does, and no toxicity is recorded for them:
- Goat's beard: the same job in a bed and the same flowering time; 12 in shorter, 8 in narrower.
- Hardy hibiscus: the same job in a bed and the same colour; 12 in shorter, 12 in narrower.
- Joe Pye weed 'Gateway': the same job in a bed; 12 in narrower, flowers late July to mid September.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
What flowers after ornamental rhubarb?
Ornamental rhubarb is over by late June. These start as it finishes and carry the same spot on, so it never goes flat:
- Delphinium: from late June to mid July, 5 ft tall.
- 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.
What does ornamental rhubarb look like in winter?
Ornamental rhubarb 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.
In these guides
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Tall perennials and grasses for the back of a border
- Plants with purple and burgundy leaves
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
- Flowers
- Late May to late June; feathery plumes; red, pink
- Leaves
- Bold texture, herbaceous; dark green, red
- Shape
- Mounding, clumping
- Hardy in
- USDA zones 5 to 7
- Light
- Full sun, part sun
- Soil
- Rich, evenly moist
- Water
- High
- Feeding
- Moderate, in spring
- Family
- Polygonaceae
Checked against ASPCA poison lists. 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.