Crop type: Sweetcorn

Zea mays ‘Earlibird’ AGM

Common name: Sweet corn ‘Earlibird’ (supersweet)

Crop slug: sweetcorn

This Allotment Pro editorial draft summarises the cited RHS cultivar profile and its linked crop guidance. Check the sources and adjust cultivation decisions for local conditions.

RHS cultivar profile

1 - Overview

‘Earlibird’ is the earliest of the supersweet sweetcorn cultivars, making it particularly useful in British summers. Each upright plant produces one or two exceptionally sweet cobs approximately 20cm long. Its good tolerance of cold soil can improve germination when seed is sown directly in place.

The cultivar holds the RHS Award of Garden Merit. Like other supersweet types, it should be isolated from other sweetcorn and maize cultivars because cross-pollination can reduce the expected sweetness. Its early August-to-September cropping window is a practical advantage where summers are short.

2 - Size

Ultimate height: 1.5–2.5 metres
Ultimate spread: 0.5–1 metre
Time to ultimate height: 1 year
Habit: Columnar and upright

Although tall, ‘Earlibird’ occupies a relatively narrow vertical space. Plant it in a compact grid so wind-borne pollen can move between tassels and silks and fill each 20cm cob evenly.

3 - Growing conditions

Suitable soils: Chalk, clay, loam or sand
Moisture: Moist but well drained
Preferred pH: 5.5–7.0, within acid, neutral or alkaline soils

Enrich the soil with well-rotted organic matter before planting. Sweetcorn tolerates a range of soil textures, but dependable drainage and moisture help the early crop establish quickly and swell its cobs.

4 - Position and hardiness

Light: Full sun
Aspect: East-, south- or west-facing
Exposure: Sheltered
Hardiness: H2 — tolerant of low temperatures but not freezing, approximately 1–5°C

Choose the warmest sheltered part of the plot and plant out only after frost. Its cold-soil germination tolerance does not make mature plants frost hardy.

5 - Colour and seasonal interest

Season	Foliage	Cobs and flowers
Spring	Green seedlings	—
Summer	Tall green leaves	Tassels, silks and developing green-husked cobs
Autumn	Declining after harvest	One or two mature 20cm yellow-kernelled cobs
Winter	Deciduous and cleared	—

The useful cultivar characters are early maturity, full well-filled 20cm cobs and the supersweet kernel type rather than ornamental colour.

6 - Botanical details

Family: Poaceae
Native to Great Britain and Ireland: No
Lifecycle: Annual
Foliage: Deciduous
Habit: Columnar and upright
Name status: Accepted
Award: RHS Award of Garden Merit

Genus

Zea is a small genus of large flowering grasses. In Zea mays, male flowers form terminal tassels while female flowers and developing cobs sit in leaf axils. Wind carries pollen down to the silks, so a block planting supports kernel set.

7 - How to grow

Cultivation

Grow in a sunny sheltered site in soil enriched with well-rotted organic matter. Preserve supersweet flavour by keeping ‘Earlibird’ away from other varieties. Sow at the packet’s specified depth and temperature, since supersweet seed can be temperamental despite this cultivar’s useful cold-soil tolerance.

The profile gives April to May for sowing, May for outside planting and August to September for the main harvest, with a broader possible harvest window from July to October. Pick when the cob silks have browned and kernel juice is creamy.

Propagation

Sow seed under cover from mid-spring in pots or modules, harden off and plant outside in May or June after the final frost. Alternatively direct-sow from late spring to early summer. Always plant ordinary sweetcorn in a grid for effective wind pollination.

Pruning

No pruning is required. Support or earth up plants if wind threatens to loosen the shallow roots.

Pests

Birds, slugs, mice and badgers may damage seed, seedlings or cobs. Indoor sowing and secure physical protection reduce losses.

Diseases

The profile lists smuts, which can form large galls on cobs and stems in hot weather. Remove affected growth and do not use damaged cobs.