How to grow arrowroot
Overview
Arrowroot (Canna edulis) is a tropical perennial grown for its starchy, edible rhizomes. It thrives in warm, frost-free conditions with consistent moisture. Growers must provide full sun and well-drained soil for best yields.
Soil Preparation
Prepare soil by incorporating well-rotted compost or aged manure to a depth of 30 cm. Aim for a pH of 6.0–7.0 with good drainage; if soil is heavy clay, raise beds or add gypsum. Sandy soils benefit from extra organic matter to retain moisture.
Growing Guide
Plant arrowroot rhizomes 5–10 cm deep and 60 cm apart in full sun and well-drained, fertile soil. Water regularly to keep soil moist but not waterlogged, and mulch heavily to retain moisture and suppress weeds. In cooler parts of subtropical zones, wait until after the last frost and consider using black plastic to warm the soil. Staking may be needed in windy areas due to tall foliage.
Care
Feed every 6–8 weeks during active growth with a balanced organic fertiliser (e.g., 5-5-5). Remove dead or yellowing leaves to improve airflow and reduce disease. Divide clumps every 2–3 years in spring to maintain vigour and replant healthy rhizomes.
Companion Planting
Good companions include sweet potato, yam, and legumes such as beans or peas, which fix nitrogen. Avoid planting with other root crops that share similar pest pressures, like potatoes or carrots.
Common Pests & Risks
Slugs and snails can damage young shoots; use beer traps or iron-based baits. Leaf rollers may chew leaves; handpick or apply Bacillus thuringiensis. In dry conditions, spider mites can occur; hose off foliage or use neem oil.
Harvesting
Harvest arrowroot rhizomes 8–10 months after planting when the leaves turn yellow and die back. Dig carefully to avoid damage, cut off tops, and use fresh or store in a cool, dry place for several weeks.
In the Kitchen
Harvested rhizomes can be boiled, baked, fried, or grated to extract starch for thickening soups and sauces. Store in a cool, dry place for up to 2 weeks; they can also be sliced and dried. Young shoots are edible as a green vegetable.
Troubleshooting
Yellow leaves: overwatering or nitrogen deficiency – reduce watering and apply balanced fertiliser. Brown leaf edges: underwatering or wind scorch – increase water and provide windbreak. Stunted growth: cold temperatures or poor soil – wait for warmth and enrich soil. Rhizome rot: waterlogged conditions – improve drainage and avoid overwatering. Holes in leaves: leaf roller caterpillars – handpick or use Bt.