How to Grow White Mustards UK

When to Plant White Mustards in the UK

When to plant white mustards in the UK: in Southern England, sow mid April to mid May. Find your area in the table below.

Region	Sow
Southern England	mid April to mid May
Midlands	mid April to mid May
Northern England	late April to late May
Scotland	early May to late May

Southern England - detail & sources

NDSU states seeding runs late April to mid-May; taken here as the equivalent UK spring window.

Midlands - detail & sources

Same spring sowing window as elsewhere in the UK -- RHS rates white mustard H4, hardy through most of the UK.

Northern England - detail & sources

Sowing window shifted about a week later than southern England for a cooler spring start -- RHS's H4 rating means winter cold is not a limiting factor even this far north.

Scotland - detail & sources

Sowing window shifted about two weeks later than southern England for Scotland's cooler, later spring -- NDSU notes cool temperatures actually extend flowering and boost yield, so this crop is well suited to a cooler northern season.

Quick Facts

Factor	Value
Drainage	Fertile, well-drained (RHS); NDSU: avoid drought-prone sandy soils, prefers good moisture.
Lifecycle	Annual herbaceous plant. RHS rates it H4, hardy through most of the UK (-10 to -5°C).
Edible parts	seeds, leaves

At a Glance

Growth Stages

Stage	BBCH	Notes
Sowing	0	NDSU: sow late April to mid-May, 0.5-1.5in deep into a moist, firm seedbed via drill or air seeder -- early planting on a firm seedbed supports vigour. RHS: propagate by seed into fertile, well-drained soil in full sun.
Seedling establishment	1	NDSU: flea beetles cause early-season "shot-holed" damage on seedlings -- treatment is only warranted once defoliation exceeds 25%. Cool temperatures and good moisture at this stage extend flowering and boost eventual yield.
Flowering	6	RHS: bright yellow flowers appear from May through to August or September, valued as a food source for wildlife.
Pod maturity and harvest	8	RHS: flowers are followed by dark red-to-brown seeds. NDSU: harvest by straight combining once pods are mature and dry, ideally at 12-15% seed moisture, around 85-90 days from sowing.

Harvest & Storage

When to pick: NDSU: harvest by straight combining once pods are mature and dry, ideally at 12-15% seed moisture for best quality -- crop matures 85-90 days from sowing.

Storage

Store dried seed in an airtight container; used to make table and hot-dog mustard, or in processed meats for flavour, emulsification and water binding (NDSU).

Diseases

Clubroot

moderate

Plasmodiophora brassicae

Named by RHS as the main UK disease risk for this brassica-family crop; NDSU's commercial-growing guidance does not mention it, instead flagging Sclerotinia -- a genuine regional difference kept honest rather than…

White mold (Sclerotinia stem rot)

moderate

Sclerotinia sclerotiorum

Named specifically by NDSU as a serious risk in commercial mustard production; recommends avoiding rotation with canola, sunflower or beans to reduce the risk. RHS does not mention it for UK garden growing.

Pests

Cabbage caterpillars

low

Pieris brassicae; Pieris rapae; Pieris napi; Mamestra brassicae; Plutella xylostella

Named by RHS as a general risk for this brassica-family crop.

Flea beetles

moderate

Chrysomelidae: Alticini (various spp.)

Named independently by both RHS and NDSU -- NDSU describes a "shot-holed" leaf appearance on seedlings, treatment warranted only above 25% defoliation.

White-mustard, Seed to Harvest

A pollinator visit

RHS notes white mustard flowers are valued as a food source for wildlife -- bees and other pollinators visit readily through the long May-to-autumn bloom period.

Flowering plants in a bed

RHS describes bright yellow flowers on hairy, erect, branched stems -- the branching habit is easy to see once a patch is in full bloom.

A dense flowering stand

White mustard's compact, branching growth means even a small planting produces a dense mass of bloom.

A field-scale planting

NDSU covers white mustard (as yellow mustard) as a genuine commercial seed crop, grown at field scale for table and hot-dog mustard production.

A close-up flower cluster

Individual flowers cluster densely at the stem tips -- this is the stage that develops into seed pods over the following weeks.

An upright flowering stem

RHS gives a mature height of 0.5-1m -- NDSU's commercial crop reaches a similar 30-45in.

Flowers and forming pods together

As lower flowers finish, pods begin forming behind them while the stem tip continues flowering -- a single plant can show every stage at once.

Grown as a green manure

RHS notes white mustard is grown for fodder, green manure or seed -- a dense planting like this is exactly what a green-manure cover crop looks like in flower.

Seed pods forming

RHS notes flowers are followed by dark red-to-brown seeds -- NDSU recommends harvesting once pods dry down to 12-15% seed moisture.

References

1. North Dakota State University Agriculture Extension - Tame Mustard Production

   Soil: fertile, well-drained, avoid drought-prone sandy soils. Size: 30-45in height, matures 85-90 days. Climate: prefers cool temperatures and good moisture, which extend flowering and boost yield. Planting: seed late April to mid-May, 0.5-1.5in deep in a moist, firm seedbed; ~100,000 seeds/lb, sown at 10-14lb/acre via grain drill or air seeder; early planting and a firm seedbed support vigour. Pests: flea beetles cause early-season "shot-holed" damage on seedlings; treat if defoliation exceeds 25%. Diseases: Sclerotinia (white mould) a serious risk -- avoid rotating with canola, sunflower or beans. Harvest: straight combine when mature and dry, ideally at 12-15% seed moisture for quality. Edible use: table and hot-dog mustard; used in processed meats for flavour, emulsification and water binding.

2. Royal Horticultural Society - Sinapis alba (white mustard)

   Hardiness H4 (-10 to -5°C, hardy through most of the UK). Soil: chalk, clay, loam, sand, fertile and well-drained. Sun/aspect: full sun, south/west-facing. Exposure: exposed or sheltered. Size: 0.5-1m height, 0.1-0.5m spread, 1 year to maturity. Propagation: by seed. Pests: flea beetles, caterpillars. Diseases: clubroot. Edible use: grown for fodder, green manure or mustard seed; native British plant, bright yellow flowers May-Aug/Sept, dark red-brown seeds, valued as a wildlife food source.

2 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.