Vegetable · Euphorbiaceae
Cassava
Manihot esculenta
A tough tropical root crop that's a snap to grow and a must to process right.
Full sun
Every 7–14 days
59–95°F · 15–35°C
240–360 days
Overview
Cassava (Manihot esculenta) is a woody tropical shrub in the spurge family (Euphorbiaceae), and it's grown for those starchy roots people love. It's a major staple crop across warm regions, feeding huge numbers of people every day. Native to South America, it's been grown for thousands of years.
Out in the garden it reaches 5 to 10 feet (1.5 to 3 m) tall and spreads 3 to 6 feet (90 to 180 cm) wide, growing at a moderate pace. It's a perennial that's outdoor only, so don't expect to keep it in a pot. Give it full sun and it's happy, though it'll put up with a bit of partial shade.
Here's the thing you can't skip: every part of the plant, roots and leaves included, holds cyanogenic glycosides that release hydrogen cyanide when the tissue gets damaged. Raw or badly processed cassava is genuinely poisonous, so it's only safe after peeling, grating or soaking, and thorough cooking.
Care
The short version: Give cassava full sun, well-drained sandy loam, and warmth between 59°F to 95°F (15°C to 35°C). Water young plants to get them going, then back off since it's drought-tolerant once established. Plant stem cuttings after frost, feed once at planting with potassium-rich NPK, and harvest the roots 8 to 18 months later before any frost hits.
Light
Cassava loves full sun, so give it the brightest spot you've got. It'll tolerate a little partial shade if it has to, but you'll get the best roots out in the open.
Water
Young plants need steady water to get established, but after that you can ease right off. Cassava is highly drought-tolerant once established, so in dry spells every 7 to 14 days is plenty. Let the top 3cm dry out between drinks, and steer clear of waterlogged soil since it brings on root rot and hurts tuber quality.
Soil
Go with well-drained sandy loam and aim for a pH of 5.5 to 6.5. Good drainage is the key here, because soggy ground is exactly what cassava can't stand.
Temperature
Keep it warm, somewhere in the 59°F to 95°F (15°C to 35°C) range. It's frost-tender, and even a touch of frost will blacken the foliage, so timing your season around the cold is essential.
Humidity
Average humidity of 40% to 70% suits cassava just fine, and it copes well with drier air too. No need to fuss over a humid setup.
Feeding
Feed it once, right at planting, with a balanced NPK that has enough potassium for root development. That potassium is what helps those roots fill out, so don't skip it.
Pruning
There's barely any pruning to do. Take off the lower lateral shoots to focus growth, and cut back any frost-killed or damaged stems. At season's end, save the healthy stems as cuttings for next year.
Repotting
not typically container-grown
Size & spacing
Plan for a plant that gets 5 to 10 feet (1.5 to 3 m) tall and spreads 3 to 6 feet (90 to 180 cm), so give each one room. It grows at a moderate pace and stays outdoors only, never in a container.
When to plant
Wondering when to do what? Cassava grows in zones 9 to 11, and the whole rhythm follows the warm season. You'll plant stakes after frost danger passes and the soil warms up, then harvest the roots well before the first frost rolls in.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Plant woody stem cuttings (stakes) after all danger of frost has passed and soil is warm.
- Harvest: Harvest roots 8-18 months after planting, once tubers have bulked.
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Cassava is pretty easygoing, but a few problems do crop up. Here are the big three to watch for, what causes them, and how to set things right.
Mottled, twisted leaves usually mean a virus
When you see that yellow-green mosaic pattern with warped, undersized leaves, you're probably looking at cassava mosaic virus. There's no cure, so the move is to pull and destroy affected plants, start clean with certified virus-free stakes, and keep whiteflies in check since they spread it around.
Fix:
- Remove and destroy infected plants
- Use virus-free planting material
- Control whitefly vectors
Blackened, drooping growth after a cold night
Did the leaves and stems turn black and flop over right after a chilly night? That's frost or chilling injury, since cassava is frost-tender. There's no saving the damaged tissue, so the smart play is to harvest roots before frost and treat the whole thing as a single warm-season crop unless you're in a truly warm zone.
Fix:
- Harvest roots before frost
- Protect or relocate if possible
Mushy, smelly roots point to too much water
If the plant is wilting up top and the tubers come up soft, discolored, and foul-smelling, you've got root rot from soggy ground. The fix is to improve drainage, ease off the watering, and dig roots promptly once they've bulked. Planting on ridges next time keeps the roots out of standing water.
Fix:
- Improve drainage
- Avoid overwatering
- Harvest promptly once mature
Toxicity
This is the part to take seriously. Cassava is a staple for millions, yet every part can be dangerous raw because of the cyanide it releases. Here's how it affects people and animals, and why processing matters so much.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
Watch for drooling, vomiting, labored breathing, and dilated pupils. As the cyanide takes hold a cat can go weak, slip into convulsions, and collapse, so this needs a vet right away.
Dogs Severe
Expect drooling, vomiting, and trouble breathing early on, often followed by staggering and seizures. It moves fast, so don't wait to call the vet if a dog chews any part.
Horses Toxic
Look for fast, distressed breathing along with trembling and stumbling. A large dose can be fatal, so any suspected mouthful is an emergency.
Rabbits Toxic
Their small bodies handle cyanide poorly, so even a little is risky. Signs include weakness, gasping, and twitching that can come on quickly.
Livestock Severe
Cattle, goats, and sheep show rapid breathing, drooling, and staggering, then muscle tremors, convulsions, and collapse. Keep raw cassava well away from grazing animals.
Birds Toxic
Poultry and pet birds get labored breathing and sudden weakness, and because they're so small, even a modest amount turns serious fast.
People Caution
Cassava feeds millions, but only after it's peeled, grated or soaked, and cooked. Raw or half-processed roots and leaves release cyanide that brings on vomiting and dizziness, and steady under-processing can cause konzo paralysis. Never eat any part raw.
Proper processing (peeling, grating/soaking, and thorough cooking) drives off the cyanide and renders cassava safe to eat; the raw plant and unprocessed roots/leaves are dangerous. Keep raw plant material away from children and animals.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
There are two broad types you'll run into, and the difference comes down to how much cyanide-forming compound they carry and how much work they need before eating.
Sweet cassava
It carries fewer cyanide-forming compounds, and most of what's there sits in the peel. Don't let the name fool you though: it still needs peeling and cooking before it's safe.
Bitter cassava
The cyanide-forming compounds run all the way through the root, so it takes heavy processing. Think grating, soaking, fermenting, and cooking before anyone can eat it safely.
How to propagate
Making more cassava is refreshingly simple. You won't bother with seeds or tubers here, just woody stem cuttings, and they take hold fast.
Stem cuttingsEasy
Plant mature woody stem cuttings (stakes) at the start of the warm season after frost danger has passed. · 2 to 4 weeks for sprouting and rooting
Forget about tubers or seed here. You'll cut stakes 20 to 30 cm long from mature, healthy stems and plant them once the warm season kicks off. New shoots and roots usually show up in about 2 to 4 weeks.
Myths
A quick boil makes any cassava safe to eat.
Not quite. Bitter types need peeling, grating, soaking, and a long cook, because a brief boil leaves too much cyanide behind. Skimping on the processing over time can lead to cyanide poisoning and konzo paralysis.
Only the roots of cassava are poisonous.
The leaves carry the same cyanide-forming compounds as the roots. Both have to be processed properly before any person or animal can safely eat them.