Crop type: Broccoli
Brassica oleracea (Italica Group) 'Cardinal'
Common name: broccoli (purple sprouting) 'Cardinal'
Crop slug: broccoli
This Allotment Pro editorial draft summarises the cited RHS cultivar profile.RHS cultivar profile
1 - Overview
'Cardinal' is an RHS Award of Garden Merit purple-sprouting broccoli grown as an annual or biennial food crop. It forms an upright, columnar plant to about 60cm tall, carrying green foliage and medium to large dark-purple spears. The tightly budded edible shoots are ready from spring into early summer, making this a hardy choice for extending broccoli harvests beyond winter.
The profile records a one-year time to maturity. Its sheltered full-sun preference, moist but freely drained soil and H5 rating suit a crop that must stand outdoors through cold conditions before its spears develop.
2 - Size
- Ultimate height
- 0.5–1m
- Ultimate spread
- 0.1–0.5m
- Time to ultimate size
- 1 year
3 - Growing conditions
- Suitable soils
- Chalk, clay, loam and sand
- Moisture
- Moist but well-drained
- Soil pH
- Alkaline or neutral
4 - Position and hardiness
- Light
- Full sun
- Aspect
- South-facing or west-facing
- Exposure
- Sheltered
- Hardiness
- H5 — hardy in most UK locations even during severe winters, tolerating temperatures in the RHS band of about -15 to -10°C
5 - Colour and seasonal interest
| Season | Flowers | Foliage | Fruit |
|---|---|---|---|
| Spring | Purple | Green | — |
| Summer | — | Green | — |
| Autumn | — | Green | — |
| Winter | — | Green | — |
The purple spring entry corresponds to the compact flower buds that form the edible spears. They should be harvested before those buds open.
6 - Botanical details
- Family
- Brassicaceae
- Native to Great Britain and Ireland
- No
- Foliage
- Deciduous
- Habit
- Columnar upright
- Name status
- Accepted
Genus
Brassicas may be annual, biennial or perennial. Most have upright growth, alternate and often blue-green leaves, long taproots and clusters of cross-shaped yellow or white flowers. Selection within the genus has produced familiar food crops including broccoli, cabbages, turnips, mustards and oilseed rape, alongside ornamental plants.
7 - How to grow
Cultivation
Grow 'Cardinal' in fertile, well-drained ground in full sun or very light shade. Its profile prefers a sheltered position, which helps an overwintering plant remain stable. Rotate broccoli with other crop families rather than planting brassicas in the same soil every year, reducing the build-up of soil-borne disease.
The parent broccoli guide gives the detailed sowing, transplanting, spacing and care sequence. Keep plants protected from brassica pests and support them where necessary until the dark-purple spears are ready.
Propagation
Propagate by seed, either starting plants indoors or sowing vegetable seed by the appropriate outdoor method.
Suggested locations
- Patio and container planting
Pruning
No shaping prune is needed. Harvest the edible heads when the spears are well formed and tightly budded, before the flowers begin to open. Continued cutting encourages side-shoots.
Pests
The profile lists susceptibility to cabbage root fly, caterpillars, cabbage whitefly and mealy cabbage aphid. Fine insect-proof mesh and regular inspection help protect young growth and developing spears.
Diseases
The profile lists club root, brassica downy mildew, brassica white blister and powdery mildews. Crop rotation, free drainage, clean planting material and adequate spacing reduce avoidable disease pressure.