How to Grow Arbi (Arvi / Colocasia) at Home in India — Pots, Grow Bags & Terrace Guide

How to Grow Arbi (Arvi / Colocasia) at Home in India — Pots, Grow Bags & Terrace Guide

Arbi — अरबी / अरवी in Hindi, कचालू (kachalu) in Punjabi, chembu (चेम्बु) in Kerala, seppankizhangu in Tamil — is one of the most reliable and fuss-free monsoon vegetables you can grow on an Indian terrace or balcony. It is planted in May or June, grows vigorously through the monsoon rains, and produces corms for harvest in October–November. The giant elephant-ear leaves are also edible — used to make Gujarat's beloved paatra, Maharashtrian alu-wadi, and South Indian patrade.

Despite being a staple of Indian cooking, arbi is almost invisible in English gardening content. Most guides focus on the ornamental elephant ear or the Hawaiian poi taro. This guide is written for Indian home gardeners — with container methods, nursery advice, regional sowing timings, and the specific varieties available at Indian markets.

May–June growers: You are in the perfect window. Arbi corms planted by June 20 will establish before the monsoon arrives, then explode into growth once the rains begin. Plant now and you will be harvesting by October.

Regional Names

Quick Facts

India Planting Calendar

What to Buy: Corms at the Nursery

Arbi is propagated from seed corms — the small to medium-sized corms sold at nurseries and local vegetable markets (sabzi mandi) in May and June. You do not need to buy from a specialty nursery; any fresh arbi corm from the sabzi mandi will work.

What to look for when buying:

• Firm and heavy — reject shrivelled, soft, or mouldy corms
• Size: medium corms (egg-sized, 50–100g) establish fastest
• Skin: intact and unbroken; a few sprouting points (eyes) are ideal
• Smell: fresh and earthy, not musty

Varieties to ask for:

• Satokaiya / Sato-imo — popular in North India; round corms, excellent flavour
• Ghaiya arbi — common in UP and Bihar; prolific side-corm production
• Muktakeshi — large corm variety for West Bengal
• For South India: ask for the local market corm — varieties vary by region

How to Grow Arbi Step by Step

Step 1: Prepare Your Container

Choose a pot or grow bag at least 30 cm deep and 30 cm wide — arbi corms swell downward as they grow, and depth is more important than width. A 25L grow bag per plant is ideal. Ensure at least 4–6 drainage holes.

Fill with a rich, moisture-retentive mix:

• 40% garden soil (or red soil for South India gardens)
• 40% well-rotted compost or vermicompost
• 20% cocopeat

Do not use purely sandy mix — arbi needs moisture retention. Do not use heavy clay alone — drainage must still be adequate.

Step 2: Plant the Corm

Dig a hole 8–10 cm deep. Place the corm with the smooth (bottom) end down and any sprouting points (eyes) facing up. If you cannot tell which end is which, lay the corm on its side — it will self-correct. Cover with 5–7 cm of soil mix; the top of the corm should be about 3–5 cm below the surface.

Water thoroughly after planting.

Step 3: Place in Partial Shade

Unlike most vegetables, arbi does not need full sun. In Indian summer heat (May–June temperatures above 38°C), partial shade is actually better — 4–5 hours of morning sun, with afternoon shade from a wall or shade net, will protect tender new growth.

Once the monsoon begins and temperatures moderate, arbi can handle full sun and will grow even faster.

Step 4: Water Consistently

Keep the soil consistently moist during the pre-monsoon establishment phase (May–June). Water every 1–2 days in hot weather. Arbi can tolerate occasional waterlogging but will rot in persistently soggy soil without drainage.

During the monsoon, natural rainfall usually handles irrigation. Reduce watering and ensure drainage holes are clear.

Step 5: Fertilise During Growth

Arbi is a heavy feeder. Apply one of the following every 4–6 weeks during the growing season:

• 1 cup vermicompost per plant
• 1/2 cup neem cake (good for soil health and pest prevention)
• Liquid fertiliser: 2 tablespoons of banana peel water or diluted cow dung slurry

Do not over-fertilise with nitrogen — this promotes lush leaf growth at the expense of corm development. Focus on phosphorus (from bone meal or DAP) and potassium (from wood ash or potassium sulphate) from August onwards to support corm swelling.

Step 6: Manage Pests (Usually Minimal)

Arbi is one of the most pest-resistant vegetables in the Indian garden. Common issues:

• Taro leaf blight (brown spots, water-soaked lesions): spray copper oxychloride 3g/L
• Aphids on new growth: neem oil spray 5ml/L every 7 days
• Corm rot in waterlogged soil: improve drainage immediately; remove affected plants

Step 7: Harvest Corms in October–November

The signal to harvest is when the lower leaves begin to yellow and the plant starts to die back naturally — usually October–November. Do not harvest too early; corms need the full growing season to reach size.

To harvest:

1. Stop watering 2 weeks before planned harvest to let soil dry slightly
2. Tip the container or dig around the plant with a trowel
3. Pull the entire root mass and separate corms by size
4. Save the small side-cormlets — these can be replanted next May as your free planting stock

Corm sizes after harvest:

• Main central corm: 100–300g — best for cooking
• Side cormlets: 20–80g — replant or eat young

Harvesting Leaves (Arbi Ke Patte)

You do not have to wait 6 months to use your arbi plant. Leaves can be harvested from 3–4 months after planting (August–September) for making paatra, patrade, or alu-wadi. Take only the older outer leaves; leave 4–5 active leaves on the plant to continue feeding the corm.

Important: Raw arbi leaves contain calcium oxalate crystals. Always cook them thoroughly — boil, steam, or cook in oil. Do not eat raw.

Common Problems

FAQ

Can I grow arbi in a pot?

Yes — arbi grows very well in pots and grow bags. Use a minimum 12–16 litre pot, 30 cm deep. Fill with a rich, moist-retentive mix: 40% soil + 40% compost + 20% cocopeat. Arbi in containers often produces smaller corms than ground-grown plants, but still yields well for home cooking.

When should I plant arbi in India?

May to mid-June is the ideal planting window across most of India. Arbi needs warmth and consistent moisture — the monsoon does most of the watering work once it arrives. In South India and coastal regions (Kerala, coastal Karnataka), you can plant as early as April.

How long does arbi take to grow in a container?

5–7 months from planting to corm harvest. Corms planted in May are typically ready to harvest by October–November. Leaves can be harvested earlier — from 3–4 months after planting.

Why are my arbi leaves turning yellow?

Mid-season yellowing is usually overwatering in poorly drained containers, or nitrogen deficiency. Add vermicompost and improve drainage. Yellowing in October–November is natural — it signals the plant is approaching harvest time.

Can I use small side-cormlets to propagate arbi?

Yes. The small cormlets that form around the main corm can be separated and planted the following May. They take slightly longer to mature but are free planting stock. This is how most Indian home gardeners replenish their arbi supply year after year.

How is arbi different from elephant ear (decorative colocasia)?

Both are Colocasia esculenta but selected for different traits. Edible arbi varieties have smaller, starchier corms and are bred for food. Ornamental elephant ears are selected for dramatic leaf colour and size, and their corms are often smaller and less palatable. For edible use, always buy corms from the sabzi mandi or a vegetable nursery — not a decorative plant nursery.

What to Grow Alongside Arbi

Arbi thrives with these companion plants in the monsoon garden:

• Lauki (Bottle Gourd) — both love moisture and heat; lauki trellises vertically while arbi fills horizontal space below
• Karela (Bitter Gourd) — similar June sowing window; place karela on trellis beside arbi containers
• Luffa/Turai — another June/monsoon vine; creates shade for arbi below
• Tinda (Apple Gourd) — fellow Indian monsoon vegetable; plant together in a kitchen garden corner
• Monsoon Garden Prep India — pre-monsoon soil preparation guide before planting arbi

Arbi / Arvi / Colocasia Monsoon Week 2 Checkpoint (Jun 8–20)

Monsoon Week 2 (June 8–20) is the defining fortnight for arbi (colocasia / taro / arvi) planted in May–early June across India. Corms planted 3–5 weeks ago are in their root establishment phase — the window where sustained waterlogging most frequently causes corm rot, and where successfully established plants begin their fastest leaf growth of the season. Here is the Week 2 state-of-garden checkpoint for arbi in Indian container and kitchen gardens.

Where Your Arbi Should Be Right Now (by planting date)

April–early May plantings (5–6 weeks old): These are your most advanced arbi plants. After 5–6 weeks in warm monsoon soil, they should carry 3–5 large unfurling leaves on firm upright petioles. The heart-shaped leaves with prominent veins are characteristic of a healthy, well-established corm. Week 2 action: Top-dress with 2–3 cm of vermicompost around the base — not touching the petioles — to feed the plant naturally. The main risk at this stage is leaf miner and taro caterpillar; inspect leaf undersides after dark.

May 15–31 plantings (3–4 weeks old): These should show 1–3 leaves on emerging petioles, typically 10–25 cm tall. Week 2 action: This is the maximum waterlogging vulnerability window. The corm has begun rooting but root mass is still limited. A 48-hour waterlogging event at this stage can kill the corm. Elevate pots on bricks; remove all saucers; probe soil after every rain event — moist is fine, muddy-saturated is dangerous.

Early June plantings (0–14 days old): Very recently planted corms in the pre-sprout phase. Arbi sprouts in 10–21 days in warm monsoon soil (28–32°C). Week 2 action: No intervention needed beyond ensuring drainage. If nothing is visible above soil at Day 14, gently probe near the corm — you should feel a small firm bud. A soft, off-smelling corm at this probe is rotted; replace immediately with a fresh corm from the market.

Week 2 Waterlogging Alert

Unlike field-grown arbi which drains freely, container-grown arbi has no escape from standing water. The corm can tolerate brief waterlogging but not sustained anaerobic conditions:

• Drainage test: After heavy rain, water should drain visibly within 5 minutes; if it's still standing at 15 minutes, the drainage hole is blocked
• Saucer removal: Critical — remove all saucers now. A saucer under an arbi pot during Week 2 monsoon keeps the root zone permanently saturated
• Elevation: Pots on brick stands drain 2–3x faster than pots sitting flat on wet terrace tiles; even 5 cm of clearance makes a significant difference
• Smell test: Sour or rotten smell from the soil = anaerobic conditions developing; act immediately

Week 2 Leaf Harvest Window (April Plantings)

If your arbi was planted in April, the first leaf harvest may be approaching in Week 2:

• Leaves are ready when 20–25 cm across and fully unfurled (no longer tightly rolled)
• Harvest outer leaves only — leave 2–3 innermost rolled leaves to continue the growing point
• The central bud (growing tip) must never be cut — it is the plant's only growing point
• Arbi leaves MUST be cooked thoroughly — raw or undercooked leaves cause severe throat irritation from calcium oxalate crystals; pressure cook or boil for 15+ minutes

Week 2 Taro Caterpillar Watch

Spodoptera litura (tobacco cutworm / taro caterpillar) is most active in Week 2's warm, humid conditions. It feeds at night on leaf margins, creating characteristic semicircular notches:

• Inspection: Check leaf undersides and the soil surface at the pot base after dark with a torch — caterpillars hide in the soil during the day
• Action: Handpick any caterpillars found and drop in soapy water; apply neem oil (5ml/L + 2ml dish soap) on both leaf surfaces every 5 days
• Reassurance: Taro caterpillar damage is cosmetic; it rarely kills arbi or reduces corm production significantly

Week 2 Action Checklist

1. Check establishment status — May plantings should show leaves; early June plantings should show sprouts
2. Elevate pots on bricks and remove all saucers — the single most impactful Week 2 action
3. Probe drainage after every rain — ensure the drainage hole is free; clear with a pencil if blocked
4. Top-dress April plantings with vermicompost — feeds the plant naturally at peak growth phase
5. Check for taro caterpillar after dark — handpick; neem oil spray preventively
6. Harvest outer leaves if April-planted and 20+ cm — cook thoroughly; never strip all leaves at once
7. Do NOT fertilise with nitrogen — arbi in warm monsoon soil grows fast enough; nitrogen delays corm formation

Arbi Week 2 Problem Triage Table (June 8–20)

Realistic Arbi Week 2 Harvest Expectations

Corm harvest: There is no corm harvest in Week 2 — arbi takes 5–7 months from planting. Corm harvest is in October–November when leaves begin dying back naturally.

Leaf harvest: Possible for April plantings if leaves are 20+ cm and fully unfurled. May plantings are 3–4 weeks from leaf harvest.

What a healthy Week 2 arbi looks like: April-planted — 3–5 large unfurled leaves (20–35 cm across), dark green, upright, heart-shaped with prominent central vein. A new rolled leaf emerging from the centre confirms active growth. May-planted — 1–3 leaves on firm petioles, the central bud clearly visible and pushing upward. Both are on track for the October–November corm harvest. The monsoon is doing its work — your job is simply to manage the drainage.

Arbi (Colocasia / Taro) Monsoon Week 3 Checkpoint (Jun 21 – Jul 4)

Monsoon Week 3 (June 21 – July 4) is the fastest vegetative growth period for arbi planted in April and May. The combination of sustained monsoon warmth (28–32°C), high humidity, and regular moisture is exactly what colocasia needs to build its corm. Week 3 is not a harvest window (corm harvest is October–November) — it is a critical growth and maintenance window. Your primary Week 3 task is protecting the root zone from waterlogging while letting the monsoon accelerate leaf and corm development.

Arbi Status by Stage — Week 3 Reality Check

Arbi planted in April (70–90 days old): These are your most established plants. By Week 3, an April-planted arbi should have 5–8 large leaves (25–40 cm across) on firm upright petioles, with new leaves continuing to emerge from the centre. The corm underground is actively expanding. Week 3 check: Count the leaves and measure the largest leaf. A healthy April-planted arbi at Week 3 has leaves that are noticeably larger than at Week 2 — each new leaf should be larger than the last. If leaf size is plateauing or new leaves are coming out smaller than previous ones, this typically signals root zone stress (waterlogging or compaction) rather than nutrient deficiency.

Arbi planted in May (35–55 days old): May-planted arbi is in the rapid establishment phase. By Week 3, these plants should have 3–5 fully unfurled leaves with a new leaf emerging from the central bud. Week 3 check: The central rolled leaf bud is the key indicator. If the bud is visible and pushing upward, the plant is establishing correctly. If the plant has stopped producing new leaves for more than 7–10 days, check the corm for rot (soft tissue, foul smell on gentle probe at the base). The most common cause of arrested growth in May-planted arbi at Week 3 is intermittent waterlogging that stresses roots without fully rotting the corm.

Arbi planted in early June (15–25 days old): These are young plants just completing establishment. Week 3 check: You should have 1–3 leaves on firm petioles. The plant should not be wilting during daytime heat — taro leaves naturally droop in peak afternoon heat (2–4 PM) but should recover by evening. Persistent wilting that does not recover by 6 PM suggests root stress. If growth appears completely arrested after 25 days with no new leaf emergence, probe gently at the corm — early rot is identifiable by soft, dark tissue.

Week 3 Leaf Harvest Window (April-Planted Only)

For April-planted arbi with 5+ large, fully unfurled leaves (25 cm+): Week 3 is an acceptable window for your first arbi patta (taro leaf) harvest for culinary use. Harvest the outermost 1–2 leaves only — never the central emerging leaf or the most recently unfurled leaves. The plant must retain at least 4 leaves at all times to continue fuelling corm development through photosynthesis.

Arbi patta preparation reminder: Raw taro leaves contain calcium oxalate crystals that cause severe throat irritation. Always cook arbi leaves fully before eating — boil for 10–15 minutes minimum, or cook in a pressure cooker. Never consume raw. Once fully cooked, the oxalic acid breaks down and the leaves are safe and nutritious.

Week 3 Waterlogging Management

Week 3 is typically the period of peak monsoon rainfall intensity across most of India. Sustained waterlogging at this stage is the primary risk for arbi:

1. Check drainage daily after heavy rain — probe the soil at 5 cm depth; if it feels saturated and smells sour, drainage is insufficient
2. Elevate containers immediately — even 8–10 cm on bricks significantly improves drainage in a cloudburst
3. Do NOT add more soil on top of waterlogged containers — this increases compaction and makes drainage worse
4. Tilt containers 10–15° if sitting in a puddle — gravity-assisted drainage during heavy rain events
5. In-ground/raised bed arbi: Ensure the bed has a clear slope or drainage channel; arbi in monsoon ground plots benefits from being in slightly raised mounds (8–10 cm above surrounding ground level)

Week 3 Pest — Taro Caterpillar (Spodoptera litura)

Week 3 is when the first significant taro caterpillar pressure arrives — the same Spodoptera moth that damages many monsoon vegetables. Identify by: irregular semicircular bite marks on the edges of arbi leaves, starting at the leaf margins and working inward. In heavy infestations, the entire leaf surface may be consumed.

Management: Handpick caterpillars at dusk and dawn (they feed at night, hide near the soil by day). Spray neem oil (5ml/L) on leaf undersides every 5–7 days. For severe infestations: Bt (Bacillus thuringiensis) spray is effective and safe for edible crops.

Week 3 Action Checklist

1. Leaf count and size check — monitor new leaf emergence; plateauing leaf size signals root stress
2. Drainage inspection — after every heavy rain; elevate containers if waterlogging detected
3. Taro caterpillar patrol — check leaf margins at dusk; handpick; neem oil spray
4. April-planted leaf harvest (optional) — harvest outermost 1–2 leaves if plant has 6+ leaves total
5. May-planted central bud check — confirm new leaf is emerging from centre; probe corm if growth arrested
6. Do NOT fertilise with nitrogen — Week 3 is not a nitrogen application window; monsoon soil is already nitrogen-active
7. Potassium application (optional) — banana peel compost tea or dilute potash solution supports corm development in Week 3; apply once during this period

Arbi Week 3 Problem Triage Table (Jun 21 – Jul 4)

Realistic Week 3 Arbi Expectations

April-planted arbi in Week 3: 5–8 large leaves; active new leaf production; corm expanding underground. First culinary leaf harvest possible if plant has 6+ leaves. No corm harvest until October–November.

May-planted arbi in Week 3: 3–5 leaves with clear new leaf emergence from the centre. Establishment complete; entering rapid vegetative growth phase. No leaf harvest yet — plant needs all leaves for corm development.

Week 3 honest note: Arbi is one of the most waterlogging-tolerant vegetables in the Indian garden, but there is a limit — standing water for more than 48–72 hours will cause root rot even in taro. The Week 3 management task is essentially one thing: keep the water moving through the root zone. Good drainage in Week 3 = a heavy October–November corm harvest. Poor drainage in Week 3 = lost corms and a wasted season.

Arbi (Colocasia / Taro) Monsoon Week 4 Checkpoint (Jul 5 – Jul 18)

Monsoon Week 4 (July 5 – July 18) is the corm-building fortnight for arbi in India — the most consequential two weeks of the growing season for underground yield. By Week 4, the monsoon has been running 5–7 weeks in most parts of India. Established arbi plants are now 60–100 cm tall with 5–10 large leaves actively photosynthesising. Every gram of starch produced in Week 4 goes directly into corm expansion. The management task shifts from "prevent waterlogging damage" to "maximise corm development while maintaining plant health through monsoon's tail."

Arbi Status by Stage — Week 4 Reality Check

April-planted arbi (now 12–14 weeks old): These plants are at maximum vegetative size in Week 4. The leaf canopy is fully expanded and the corm underground is actively developing. A healthy April-planted arbi in Week 4 shows: 8–12 large (40–60 cm) leaves, a thick pseudostem of 4–6 cm diameter at the base, and — if you carefully scrape the soil surface — a visible corm 5–8 cm in diameter just below. Week 4 check: is new leaf emergence still happening? Each new leaf represents continued vigour. If no new leaf has emerged in 10–12 days, the plant has likely hit a nutrient ceiling.

May-planted arbi (now 8–10 weeks old): These plants should have 6–9 leaves and be in their fastest corm-development phase. The corm is forming rapidly from the energy of the expanding leaf canopy. Week 4 is when the difference between well-fertilised May plants and unfertilised ones becomes pronounced: fertilised plants at this stage have noticeably larger petioles and more turgid, upright leaf posture.

Container arbi (any stage): Container plants face a specific Week 4 challenge: root density. By this point, roots have likely filled the container and may be beginning to circle. This root-crowding slightly limits corm expansion. Week 4 check: lift the container — does it feel extremely heavy? If yes, the corm is developing well. If light, the plant is not storing starch effectively.

Week 4 Corm Development Support

Potassium is the Week 4 priority nutrient. Potassium directly drives starch synthesis and corm expansion. A single potassium-focused application in Week 4 can increase final corm weight by 15–25%.

• Banana peel compost tea (5–7 peels boiled in 2L water, cooled, diluted 1:5): apply around the root zone
• Muriate of potash (MOP) at 5g per plant: broadcast around base and water in
• DO NOT use nitrogen-heavy fertiliser in Week 4 — this pushes the plant toward leaf production at the cost of corm development

Mulch the base in Week 4: A 5–8 cm mulch layer of dry leaves or rice straw around the base of arbi plants in Week 4 serves three purposes: (1) maintains soil moisture between rain events, (2) keeps the top corm cool, and (3) blocks the sporadic direct sun between monsoon clouds that can scorch the surface corm.

Week 4 Pest — Taro Caterpillar Peak

Spodoptera litura (tobacco caterpillar / taro caterpillar) reaches its peak population in Week 4 of the Indian monsoon. These dark, striped caterpillars feed aggressively on the large arbi leaves, creating large irregular holes or completely defoliating individual leaves overnight.

Week 4 taro caterpillar management:

1. Evening inspection: Check plants at dusk — caterpillars feed at night and hide under the large leaves or in the leaf axils during the day
2. Hand removal: Wearing gloves, remove all visible caterpillars and drop into soapy water
3. Bt spray: Bacillus thuringiensis var. kurstaki on the undersides of leaves — effective on young (1–3 cm) larvae
4. Chlorpyrifos 20 EC (0.5ml/L) on severely affected plants: If more than 30% of leaf area is damaged and hand-picking is not controlling the population, one application of Chlorpyrifos is effective — withholding period for leaf harvest is 7 days
5. Do not damage the growing tip: Even if the outer leaves are heavily damaged, protect the central growing cone — the plant will regenerate leaves from this point

Leaf harvest consideration: If you are growing arbi for both leaves and corms, Week 4 is the last practical window to harvest leaves without affecting corm development. Take only the 2–3 outermost leaves; leave the inner 6+ leaves intact to maintain photosynthetic capacity for corm building.

Week 4 Action Checklist

1. Potassium feed: Banana peel tea or MOP around root zone; no nitrogen feed
2. Mulch application: 5–8 cm mulch layer around base
3. Caterpillar patrol: Evening inspection; hand-pick; Bt spray on young larvae
4. Drainage maintenance: Check drain holes in containers; ensure water flow after heavy rain
5. Final leaf harvest (optional): Take 2–3 outermost leaves only if desired; leave inner leaves untouched
6. Corm depth check: Gently press soil surface — the developing corm should feel firm and round; softness indicates rot beginning

Arbi Week 4 Problem Triage Table (Jul 5 – Jul 18)

Realistic Week 4 Arbi Expectations

April-planted arbi in Week 4: Maximum size; 8–12 leaves; corm 5–8 cm diameter underground; entering peak corm-building phase. No corm harvest yet — October is the window.

May-planted arbi in Week 4: 6–9 leaves; actively growing; corm just beginning to bulk up. The fastest corm expansion period of the year.

Week 4 honest note: Week 4 arbi management is essentially one decision: do you protect the corm-building process with potassium, mulch, and pest control, or do you let the plant coast? Coasting works — arbi is vigorous enough to produce a reasonable corm without Week 4 intervention. But the gardener who adds potassium in Week 4 harvests corms that are noticeably heavier in October. The investment is minimal; the payoff in October is clear.

Arbi / Colocasia / Arvi Monsoon Week 5 Checkpoint (Jul 19 – Aug 1)

Monsoon Week 5 (July 19 – August 1) is the corm-building peak for arbi in India — the fortnight when the underground corms are growing most rapidly and the management decisions made now will determine the October harvest weight. By Week 5, well-established arbi plants have typically produced a full canopy of large, deeply veined leaves and the underground system has expanded significantly from the original planting. The monsoon’s reduced but still significant rainfall in Week 5 keeps the soil moisture ideal for corm expansion, and the slightly longer dry intervals between Week 5 rain events reduce the waterlogging risk that was the primary threat in Weeks 1–3.

Arbi Status — Week 5 Reality Check

May-planted arbi (14–16 weeks from planting): These plants are approaching their corm maturation window. Week 5 check: Are the oldest (outermost) leaves beginning to yellow at the tips? Tip yellowing on the oldest leaves in Week 5 is a normal senescence signal — the plant is beginning to redirect energy from canopy maintenance to corm storage. This is not a deficiency; it is the harvest countdown beginning. Remove yellowing leaves at the base to prevent fungal disease entry at the decaying petiole.

June-planted arbi (6–8 weeks from planting): These plants are in peak vegetative growth. Week 5 check: Has each plant produced at least 4–6 full-sized leaves (50–80 cm wide)? If yes, the corm-building phase is fully underway. Apply the Week 5 potassium feed now — the timing is critical for June plantings because the corm expansion window is shorter for them than for May plantings.

Week 5 — The Potassium Investment

Potassium is the most important nutrient for corm size and starch quality in arbi. The Week 5 potassium application is the highest-ROI garden action for this crop in the entire season.

Week 5 potassium protocol:

• Potassium sulphate 2g/L: Soil drench at the base of each plant; avoid wetting the petiole base (rot risk)
• Banana peel water alternative: Ferment 3–4 banana peels in 1L water for 48 hours; dilute 1:3 with water; apply as soil drench
• Application timing: Apply on a morning with no rain forecast for 4+ hours; the potassium needs to reach the root zone without being immediately washed out
• Do not apply nitrogen: Any nitrogen fertiliser in Week 5 triggers leafy vegetative growth at the expense of corm expansion

Week 5 — Taro Caterpillar and Aphid Management

Week 5 brings two pest pressure peaks for arbi that require active management:

Taro caterpillar (Spodoptera litura): The caterpillars that hatched from Week 3–4 egg masses are now at their most destructive larval stage in Week 5. A single caterpillar can consume a full arbi leaf in 48 hours. Week 5 caterpillar management:

1. Evening inspection (mandatory): Caterpillars feed at night; inspect undersides of all large leaves at dusk
2. Manual removal: Collect caterpillars in soapy water; wear gloves
3. Spinosad spray: If infestation is heavy (>2 caterpillars per plant), apply spinosad 0.5ml/L at dusk; do not apply in rain

Aphid colonies on petioles: Week 5’s slightly drier conditions favour aphid population explosions on arbi petiole bases. Management: Strong water jet to dislodge; neem oil 5ml/L spray if colonies persist; yellow sticky traps around plant perimeter.

Week 5 — Drainage Maintenance

The corm-expansion phase requires consistently moist but not waterlogged soil. Week 5’s rain events, while less frequent than Weeks 1–4, are still significant. Week 5 drainage check:

• Confirm water drains from container or bed within 2 hours of rain
• If standing water persists beyond 2 hours, add drainage channels or tilt containers
• Maintain 5–10 cm of mulch over root zone — this buffers the wet-dry oscillation without causing waterlogging

Week 5 Action Checklist

1. Apply potassium sulphate 2g/L drench: On a dry morning; once in Week 5; critical for corm size
2. Remove tip-yellowing oldest leaves: Cut at petiole base; do not leave stubs (rot entry points)
3. Evening caterpillar patrol: Inspect every plant at dusk; manual removal or spinosad if >2 caterpillars per plant
4. Check aphid colonies on petioles: Neem oil 5ml/L if colonies present
5. Drainage check: Confirm no standing water persisting beyond 2 hours after rain
6. Mulch maintenance: Top up mulch to 8 cm if it has been washed thin by monsoon rains

Arbi Week 5 Problem Triage Table (Jul 19 – Aug 1)

Realistic Week 5 Arbi Expectations

A May-planted arbi in Week 5: 80–120 cm tall; full canopy of 6–8 large leaves; outermost leaves beginning to yellow at tips (normal); potassium drench applied; caterpillar patrol active.

A June-planted arbi in Week 5: 50–70 cm; 4–6 full-sized leaves; corm expansion underway; potassium drench applied this week.

Week 5 honest note: Week 5 is when the arbi garden delivers on its season’s promise — quietly, underground, where neither the gardener nor the visitor can see it. The corms expanding in the Week 5 soil will be harvested in October, and their weight and quality will reflect every potassium application, every caterpillar removed, every drainage channel that drained within two hours. The Week 5 gardener’s task is to stay consistent: the potassium drench, the evening patrol, the drainage check. None of these actions are dramatic. Together, they are the difference between a 500g corm and an 800g corm at October harvest.