Cassava

Quick facts

Category

roots bulbs

Difficulty

intermediate

Days to harvest

240 to 365 days

Harvest type

single harvest then replant

Spacing

100 cm between plants

Environment

Temperature

20–35°C

pH

5.5 to 7.5

EC (hydroponic)

1 to 1.8 mS/cm

Daily light

18 to 28 mol/m²/day

Climate and zones

USDA zones

9 to 13 (winter low around -7°C or warmer)

Frost tolerance

frost sensitive (dies at first frost)

Season

year-round tropical (needs consistent warmth)

Viable growing environments:

• outdoor year-round (in zone)
• outdoor in growing season (annual)
• heated greenhouse

USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.

Growing systems

Cassava works in:

• soil bed

Root mass is very heavy - thin-channel systems (NFT, vertical towers) can't hold this crop mechanically, hence the system list above.

Growing media

The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (cassava works in the media listed below).

Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.

Nutrient demand by stage

NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.

Companion-growing notes

• Heavy uptake of potassium. Co-grown crops with the same demand will end up deficient even at "correct" EC. Plan around this in shared reservoirs.

Aquaponics suitability

Not recommended for pure aquaponics. Fish waste alone doesn't provide enough of the nutrients this crop demands (typically potassium, calcium, or boron). It can be grown in a hybrid system where the reservoir is supplemented with hydroponic-style nutrients, but expect to dose actively.

Care notes

A tropical crop not suited to conventional small-scale hydroponics, but relevant to outdoor aquaponics in tropical regions. The large root system and 8-18 month growing cycle require in-ground planting or very large containers (60 L). Propagation is by stem cuttings (20–30 cm pieces of mature stem pushed into moist soil at an angle), not seeds. Temperature: 25–35°C year-round (strictly tropical; dies below 10°C). Full sun (DLI 20+ mol/m2/day). pH 5.5-6.5 (tolerates acidic conditions that most crops cannot). The plant is a light feeder by tropical crop standards and grows in nutrient-poor conditions, but responds to fertilization with increased root yield. Harvest when roots are full-sized (8-18 months from planting depending on variety). Critical safety note: bitter cassava varieties contain toxic levels of cyanogenic glycosides and must be processed (peeled, soaked, fermented, and/or dried) before eating. Consuming inadequately processed bitter cassava can cause cyanide poisoning. Sweet varieties require only peeling and cooking (boiling, frying, or roasting). For tropical aquaponics, cassava planted in beds irrigated by fish system effluent produces well and makes efficient use of the warm, nutrient-rich water.

Notable varieties

A starting shortlist of cultivars worth knowing about. Not exhaustive: the seed catalogs list hundreds of named varieties. These are the ones home growers commonly choose between.

Further reading

• Best crops for hydroponic beginners
• The Kratky method: grow lettuce with zero electricity