rhubarb

Photo: Krzysztof Golik — CC BY-SA 4.0 · source

Survives zone 3 through 8

Harvest calendar

Best planted in early spring after your last frost, or in fall before the ground freezes, depending on your climate.

⚠ STALKS ONLY — the leaf blades are toxic (soluble oxalates and anthraquinone glycosides) and must never be eaten; only the leaf stalks (petioles) are food, and they are cooked. Sharp and superb. Herbaceous, and its vernalization requirement differs from fruit-tree chill.

Hardiness

Zone 3–8

Habit

Herb

Edible part

Shoot

Ripens

April–June

Mature size

Large crown 1–1.5 m tall and as much across in full leaf; containerable in a big pot

Light

Full sun to partial (one of the more shade-tolerant crops)

Soil pH

6.0–6.8

Environment

Montane

Native range

Southern Siberia and Mongolia — a cold-continental plant, which is why it needs a proper winter chill to crop well and sulks in mild-winter climates.

Status

Cultivated

Years to fruit

2 yrs (don't crop in yr 1)

Growth speed

Moderate — a crown reaches full cropping size in its third year

Spacing

100 cm (39 in) apart — about 1 m² (11 sq ft) per plant

Leaf shape

Very large triangular to heart-shaped blades up to 60 cm across, crinkled and coarsely wavy-edged, on the thick red or green petioles that are the crop. ⚠ The blade is toxic (oxalic acid and anthraquinone glycosides) — only the stalk is food.

Root system

A massive woody crown over thick fleshy storage roots reaching 60–120 cm down. That store is what pushes the spring crop, and why pulling too hard in year one or two ruins a plant for years afterwards.

Fruit description

Not a fruit despite its use as one: rhubarb is a vegetable stalk. Flowering stems, when they appear, carry sprays of small greenish flowers and papery three-winged seeds — cut them out at the base as soon as they show, since flowering diverts the crown's reserves away from next year's stalks.

Propagation

Division of a dormant crown in late autumn or early spring — each piece needs at least one fat bud. Seed does not come true and is worth it only for breeding. Forcing under a bin or terracotta pot in late winter gives pale, tender, early stalks at the cost of the crown's strength.

Pollination

Self-fertile

The edible parts listed above are a starting point, not a field guide. Identify a plant with certainty — ideally against a local authority — before eating any part of it, and read the full disclaimer. Spotted something wrong? Report it.