How to Grow Marrowstem Kale

Soil & Growing Conditions

Water: moist, well-drained (PFAF)

Soil pH range

4.2 8.3

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

Stage	BBCH	Notes
Sowing	0	Direct seed outdoors in April/May into a seedbed (PFAF).
Transplanting	1	Transplant summer seedlings to their permanent position, avoiding overcrowding, which causes legginess; deeper planting encourages stronger root formation (PFAF).
Stem and leaf growth	3	Grows to about 0.9m (3ft) tall, developing its characteristic large, succulent, nutritious main stalk (PFAF).
Winter harvest	8	Extremely cold-tolerant, to about -15°C; prized for winter harvesting in cold climates once other crops have finished (PFAF).

Quick Facts

Factor	Value
Soil pH	4.2 - 8.3
Soil texture	light, medium or heavy soil, prefers heavy/clay (PFAF)
Drainage	well-drained
Lifecycle	biennial or perennial
Edible parts	leaves, young flowering shoots, stem

At a Glance

Harvest & Storage

When to pick: Prized for winter harvesting in cold climates; extremely cold-tolerant to about -15°C. Foliage toughens with age, so leaves are best used young; young flowering shoots taste similar to sprouting broccoli when cooked (PFAF).

Diseases

Club root

moderate

Plasmodiophora brassicae

Likely rather than confirmed: no source names this crop directly, but it shares a species (Brassica oleracea) with Kale, which lists this disease.

Downy mildew (general)

moderate

Likely rather than confirmed: no source names this crop directly, but it shares a species (Brassica oleracea) with Kale, which lists this disease.

Pests

Cabbage root fly (US: cabbage maggot)

moderate

Delia radicum

Likely rather than confirmed: no source names this crop directly, but it shares a species (Brassica oleracea) with Kale, which lists this pest.

Flea beetles

moderate

Chrysomelidae: Alticini (various spp.)

Likely rather than confirmed: no source names this crop directly, but it shares a species (Brassica oleracea) with Kale, which lists this pest.

Marrowstem Kale, Grown for the Stem

The stem is the crop

Unlike other kales it is grown for a stem that thickens club-like from about 1cm to 4-5cm, traditionally cut for winter fodder and equally edible young.

Blue-green leaves, pale stem

Young plants look like a loose collard until the stem starts to swell -- that swelling is the quickest way to confirm you have the right variety.

Sources

1. PFAF (Plants For A Future) - Brassica oleracea medullosa (Marrow-Stem Kale)

   A secondary gardening reference rather than a university or horticultural authority, used as the sole source for this heritage forage/fodder kale as no RHS or equivalent authority growing profile exists for it, explicitly disclosed. A biennial/perennial plant reaching 0.9m (3ft) tall. Foliage has a strong cabbage flavour, becoming tougher as it ages. Young flowering shoots taste similar to sprouting broccoli when cooked. Native to European coasts including the UK, Germany, Spain and France -- a cultivated form, not found wild. Extremely cold-tolerant, withstanding temperatures down to about -15°C, and tolerates high summer heat. Adaptable to full sun, semi-shade or shade, performing well on a north border. Soil: light, medium or heavy; pH 4.2-8.3; prefers well-drained, fertile, heavy soil, succeeds in heavy clay. Propagate by direct seeding outdoors April/May in a seedbed; transplant summer seedlings to permanent positions, avoiding overcrowding to prevent legginess; deeper planting encourages root formation. Not often cultivated for its edible leaves specifically, due to coarser texture than other kale varieties, but prized for winter harvesting in cold climates. Traditionally grown as a tall dairy-cattle forage crop for autumn use, as distinct from the dwarf Thousandhead type grown for sheep in winter.

2. Plants For A Future (PFAF) - Brassica oleracea

   PFAF entry for Brassica oleracea, the parent species of this cultivar group -- the figure is species-level, not cultivar-specific. Fetched and parsed directly for the USDA hardiness rating.

These 2 sources are specific to this region. The full list of 2 sources behind this guide (PFAF (Plants For A Future), Plants For A Future (PFAF)) is in the references of our UK guide to marrowstem kale; they describe the plant itself, which is the same wherever it grows.