Botanical classification (APG IV)

• Botanical name: Armoracia rusticana P. Gaertn., B. Mey. & Scherb.

• Common name: horseradish

• Family: Brassicaceae

• Order: Brassicales

Modern clades (phylogenetic):

• Angiosperms

• Eudicots

• Core eudicots

• Rosids

• Domain: Eukaryota

• Kingdom: Plantae

Cultivation and growth conditions

Climate

Horseradish is a hardy perennial herb suited to temperate climates. It tolerates cold winters, including frost and snow, thanks to its robust root system, and prefers mild to moderately warm summers. Persistent high temperatures combined with drought lead to fibrous, poor-quality roots with reduced pungency.

Exposure

The crop performs best in full sun, where it develops a vigorous leaf canopy and well-formed roots. It tolerates light partial shade, but under strong shade root yield decreases and roots tend to be thinner and of lower quality.

Soil

For good root production, horseradish prefers soils that are:

• Deep, to allow the long taproot to develop;

• Loose, friable and well drained (loam or loam-sandy);

• With good porosity, free from stones and severe compaction;

• With a slightly acidic to neutral pH (about 6.0–7.5);

• With a moderate level of organic matter.

Shallow, compact, or stony soils cause misshapen roots and reduce yield and quality. Prolonged waterlogging favours root rots.

Irrigation

Horseradish needs a consistently fresh soil, especially:

• During establishment of root cuttings (“sets”);

• Throughout active leaf growth;

• During root thickening.

The goal is to keep the soil moist but not saturated:

• Excessive dryness leads to woody, fibrous roots with low pungency;

• Excess water produces watery, poorly flavoured roots and increases the risk of rots.

Once well established in open field, plantings generally require only supplemental irrigation during dry spells.

Temperature

The favourable temperature range during active growth is roughly 10–22/24 °C.

• Plants tolerate sub-zero temperatures during winter dormancy without problems.

• In spring, mild temperatures support regular vegetative growth and root development.

• Very hot summers combined with limited water availability reduce root quality and aroma.

Fertilization

Nutrient requirements are moderate, but good fertility improves yield and root quality:

• Organic matter (well-matured compost or manure) applied before planting to improve soil structure, porosity, and water-holding capacity.

• Nitrogen (N): Useful in early stages to support leaf growth; excessive nitrogen should be avoided because it promotes overly lush foliage and less compact roots.

• Phosphorus (P): Important for root development and overall plant vigour.

• Potassium (K): Essential for root quality, stress tolerance, and storability.

Ideally, fertilization is based on soil analysis and on the intensity of cultivation (home garden vs. specialised production).

Crop care

• Soil preparation: Deep tillage (e.g. digging or light ploughing) followed by careful surface refinement to obtain a soft, stone-free profile that allows roots to grow straight.

• Planting: Usually done with root pieces (“sets”) 15–20 cm long and about 1–2 cm in diameter, planted obliquely or almost vertically with the upper end just below soil level.

• Weed control: Particularly important in the first year. Shallow hoeing or organic mulches help limit competition and maintain soil moisture.

• Spread control: Horseradish tends to naturalise easily through root fragments. In small gardens it is often useful to confine it to a dedicated bed or use physical barriers in the soil to avoid unwanted spreading.

The crop is generally robust from the plant health standpoint; problems mainly arise under waterlogged conditions (root rots) or with high pressure of pests and diseases typical of Brassicaceae.

Harvest

The root is normally harvested:

• In late autumn or early winter, after the first frosts when the aerial part has withered; or

• In late winter–early spring, before full vegetative regrowth.

Main roots are lifted carefully to avoid breakage. The best-formed pieces are destined for consumption or processing, while selected segments can be reserved as planting material for the following season.

Optimum quality (pungency, aroma) is often obtained in the first to second year of cultivation on a given root.

Propagation

Horseradish is propagated almost exclusively vegetatively, via:

• Root cuttings (sets):

  • Healthy, rot-free segments 1–2 cm in diameter and 15–20 cm in length;

  • Planted in autumn or late winter in deep, well-prepared soil.

Seed propagation is rarely used, since viable seed production is limited in many areas and vegetative propagation is simpler, faster, and ensures uniformity of plant characteristics.