Blood Amaranth: How to Grow & Harvest (UK)

Diseases

Damping-off (seedling collapse)

moderate

Rhizoctonia solani

Damping-off (seedling collapse at soil line); Wilting with chlorotic, dropping leaves

Documented for amaranth broadly (Ghana peri-urban survey; UF/IFAS).

Wet rot / stem rot

high

Choanephora cucurbitarum

Water-soaked wet rot with white silky mycelium

Main fungal disease of concern per UF/IFAS; among most prevalent in Ghana survey.

Anthracnose

moderate

Colletotrichum spp.

Sunken reddish-brown lesions with yellow halo (anthracnose)

Observed in 91% of surveyed farms in Ghana study.

Amaranthus virus diseases (unspecified/unidentified)

unknown

RHS: "may be susceptible to a virus" -- no specific virus identified.

Pests

Amaranth stem weevil and leaf-feeding caterpillars

moderate

Hypolixus truncatulus; Spodoptera spp.; Hymenia recurvalis

Grain amaranth species named explicitly by UF/IFAS as hosting stem weevil and leaf caterpillars.

Aphids

unknown

Aphididae (various spp.)

RHS: "may be susceptible to aphids".

Quick Facts

Factor	Value
Soil pH	6.5 - 7.5
Optimal growing temp	22-28°C
Minimum growing temp	10°C
Soil texture	Chalk, loam, sand; grain-production soils medium-to-high in P and K
Drainage	Moist but well-drained
Lifecycle	Annual.
Edible parts	seeds, leaves
Documented problems	4 diseases, 2 pests

At a Glance

When to Plant Blood Amaranth in the UK

When to plant blood amaranth in the UK: across the UK, sow early April to early May (an estimate: no source gives a figure for this region).

Region	Sow
United Kingdom derived	early April to early May

Rows marked derived are interpolated between regions our sources do state, because no source we consulted gives a figure for that region specifically. They are deliberately wider to reflect that uncertainty.

United Kingdom - detail & sources

The RHS entry for this species records hardiness but no sowing month, so the window here follows the species-level guidance in Ecocrop: sow in late spring where the plants are to grow, or start earlier under glass and plant out only once the last frost has passed. The plant is frost-tender (RHS hardiness H2, 1-5°C) and dies below about 4°C, so an April start belongs under cover, not outdoors.

Soil & Growing Conditions

Water: Full sun, sheltered site. Moderately fertile, humus-rich, moist soil; water freely in summer to prolong flowering. Drought resistant (RHS). Frost-tender (RHS hardiness H2, 1-5°C). For grain production specifically, optimal soil pH 6.5-7.5 (Univ. of Wisconsin Extension); RHS notes broader ornamental-garden tolerance of acid-to-alkaline soils.

Soil pH range

6.5 7.5

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

Growth Stages

Stage	Notes
Establishment	Propagate by seed (RHS); for grain production, seed diluted with carrier and drilled at ~5 lb/acre (Univ. Wisconsin Extension).
Vegetative Growth	Upright annual to 2m tall, purple-flushed dark green ovate leaves (RHS).
Flowering	Clusters of tiny reddish-pink flowers in upright to arching spikes, summer into autumn (RHS).
Fruit Development	Grain-type seed heads develop after flowering.
Ripening / Harvest	Grain harvested once seed heads dry and thresh freely (general grain-amaranth practice; needs species-specific day-count verification).
Senescence / Dormancy	Frost-tender annual (RHS hardiness H2); time to maturity ~1 year (RHS).

Harvest & Storage

When to pick: Two harvests come off one plant, and they are read differently. Leaves: the first picking is ready roughly 30-50 days after sowing, and the plant will keep giving cuttings for many months afterwards (Ecocrop, via Useful Temperate Plants). Grain: the seed head is left standing until it dries down and the seed threshes free when a head is rubbed between the fingers. In a cool summer the crop rarely dries fully on its own -- the Alternative Field Crops Manual (Purdue NewCROP) states that "a killing frost must occur before harvest followed by a week of good drying weather", and Iowa State Extension likewise has growers wait until about a week after the first hard frost. Cut before the heads begin to shatter or the plants lodge, since seed lost that way cannot be recovered.

Blood Amaranth, a Dual-Purpose Grain and Leaf Crop

Two crops from one plant

Ecocrop: the first cutting of mild, spinach-like leaves comes 30-50 days after sowing, and the same plant keeps producing for months while the seed head fills.

The grain sits in the flower head

Every one of those tiny crimson flowers sets a seed. The panicle is left standing until it dries down and the grain threshes free when a head is rubbed between the fingers.

Frost-tender, so it starts under cover

RHS hardiness H2 (1-5°C): the plant dies below about 4°C. Sow late spring where it is to grow, or start under glass and plant out only once the last frost has passed.

Full sun and a sheltered site

RHS: full sun, moderately fertile humus-rich soil kept moist, watered freely through summer. Drought resistant once established, but it will not thrive in shade.

Harvest is triggered by frost, not a calendar

Alternative Field Crops Manual (Purdue NewCROP): "a killing frost must occur before harvest followed by a week of good drying weather." Iowa State Extension advises the same week-after-frost wait.

Go easy on the nitrogen if you eat the leaves

Grown on nitrogen-rich soil, amaranth concentrates nitrates in its foliage. Feed for steady growth rather than pushing it hard when the leaves are destined for the kitchen.

It reaches 1.5-2.5m in a good season

RHS gives an ultimate height of 1.5-2.5m with a spread of 0.1-0.5m, reached within a single year. Give it room and shelter from wind, which topples loaded seed heads.

One name, three different species

"Amaranth" on a seed packet may mean this species, love-lies-bleeding (A. caudatus) or A. hypochondriacus. Check the botanical name if you are buying for grain rather than colour.

References

1. African Journal of Agricultural Research (peer-reviewed; Appiah-Kubi et al. 2022, DOI 10.5897/AJAR2022.15985) - Survey of fungal diseases associated with amaranth (Amaranthus species) in peri-urban vegetable farms in Kumasi and Tamale metropolis of Ghana

   Field survey of 43 peri-urban Amaranthus farms; identifies anthracnose (Colletotrichum), wet rot (Choanephora cucurbitarum), wilting/damping-off (Fusarium, associated genera), and stem canker (Phoma/Alternaria) as the major fungal diseases.

2. FAO EcoCrop - Amaranthus cruentus data sheet
3. GBIF - GBIF Backbone Taxonomy match: Amaranthus cruentus
4. Iowa State University Extension and Outreach - Amaranth (Alternative Agriculture)

   Independent corroboration of the frost-then-dry harvest trigger given by the Alternative Field Crops Manual: northern growers wait about a week after the first hard frost, balancing field drying against pre-harvest loss from lodging and seed shatter.

5. Purdue University Extension - Amaranth | Purdue NewCROP
6. Royal Horticultural Society - Amaranthus cruentus | purple amaranth
7. University of Florida IFAS Extension - HS1407: Production Guide of Vegetable Amaranth for Florida

   Specifically about vegetable amaranth (A. tricolor), a DIFFERENT species from A. caudatus/cruentus/hypochondriacus. Used only for: (a) confirming caudatus/cruentus/hypochondriacus are the grain-type Amaranthus species, and (b) pest genera (stem weevil, leaf caterpillars) that the source itself sources from CABI as genus-wide. Explicitly NOT used for A.-tricolor-specific growing-condition numbers.

8. University of Wisconsin-Madison Division of Extension - Amaranth (grain amaranth production)

   Addresses grain amaranth production generally (primarily A. hypochondriacus / A. cruentus, the commercial US grain species); not species-disambiguated in the source itself.

9. Useful Temperate Plants (theferns.info) - Amaranthus cruentus

   Original habitat obscure, probably tropical America. Vigorous annual to about 1m with branched stems and terminal flower spikes. Optimal temperature 22-28°C, tolerating 10-45°C but dying below 4°C. Prefers well-drained fertile soil in a sunny position, pH 5.5-7 preferred, tolerating 4.3-7.5. Sow in late spring where plants are to grow, or raise under glass and transplant after the last frosts; germination improves with warm soil and a drop in overnight temperature. EDIBLE PARTS: leaves cooked like spinach, mild-flavoured and rich in vitamins A and C, iron and calcium; seeds highly nutritious, eaten cooked, ground into flour or sprouted. First leaf harvest 30-50 days after sowing, continuing for up to 250 days more. CAUTION: on nitrogen-rich soils the plant concentrates NITRATES in the leaves.

9 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.