Langsat (Duku) care

Light

Langsat is what florists mean by "bright spot, no direct sun" — close enough to a south or east window to feel the brightness, with a sheer curtain or a few feet of distance keeping the sun off the leaves. A natural forest understorey tree tolerant of dappled to partial shade, especially when young. Mature trees produce best under high light conditions — 60–70% of full sun. In cultivation, inter-planting under taller trees or open shade structures mimics its natural habitat and reduces heat stress. A phone lux-meter at the leaf surface should read 1,500-3,000 lux at noon.

Watering

Water langsat 2–3 times per week; more frequently in dry season. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Prefers evenly moist soil and is sensitive to prolonged drought, which causes leaf drop and fruit abortion. A distinct dry season of 1–3 months, however, promotes flowering. Drip irrigation targeting the root zone is ideal; avoid wetting the trunk to prevent fungal issues.

Soil and pot

Langsat grows best in deep, well-drained clay loam or sandy clay loam, rich in organic matter. Thrives in deep, fertile, slightly acidic soil (pH 5.5–6.5). Intolerant of waterlogging — root aeration is critical. Mulch the root zone generously with wood chips or compost to retain moisture, regulate temperature, and suppress weeds without compacting soil around the trunk. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Langsat sits happiest at around 70–90% RH humidity and 20–35°C (68–95°F). Native to humid tropical regions of Southeast Asia where humidity rarely drops below 70%. Extended low-humidity periods cause tip burn and poor fruit development. In subtropical marginal climates, irrigation frequency and canopy cover help maintain adequate microclimate humidity. If you keep the room above 20–35°C year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed langsat sparingly. Apply a balanced NPK fertiliser (e.g. 8-8-8 or 12-12-17) every 2–3 months during the active growing season. Switch to a low-nitrogen, high-potassium formula as flowering approaches. Organic compost applications twice yearly improve soil biology and long-term fertility. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on langsat in the Growli community. Each is annotated with the most common cause so you know where to start.

• Irregular or absent fruiting — Langsat is notoriously inconsistent without a clear seasonal dry period to trigger flower induction. Trees in perpetually wet climates may stay vegetative for years. A controlled 6–8 week period of reduced irrigation mimicking a dry season is the most reliable way to stimulate flowering.
• Bark-eating borers — Stem and bark borers (Zeuzera spp., various longicorn beetles) can girdle young branches, causing sudden dieback. Regular trunk inspection, removal of affected branches, and application of contact insecticide into bore holes are recommended. Maintain tree vigour with balanced nutrition.
• Fruit drop before maturity — Premature fruit drop is linked to water stress, nutrient deficiency (especially potassium and boron), or pest pressure during fruit set. Maintain consistent irrigation, apply foliar boron at fruit set, and monitor for fruit-boring insects. Mulching reduces soil temperature fluctuations that stress the root system.

Propagation

Seed sown fresh (germinates in 2–3 weeks at 28–30°C); seedling trees take 10–15 years to fruit. Grafting onto seedling Lansium rootstock accelerates production to 4–6 years. Air-layering is used successfully, producing fruiting plants within 3–4 years. The superior 'Longkong' and 'Duku-Longkong' selections are propagated vegetatively to preserve fruit quality. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Langsat is pet-safe. Lansium parasiticum is not listed by ASPCA. The Meliaceae family has no widely documented toxic principle to dogs or cats. The fruit flesh is consumed safely by humans, and no veterinary toxicity cases have been recorded for this species. The seeds are bitter and may cause mild gastric upset if ingested in quantity. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Langsat deep-dive guides

Every aspect of langsat care, each with its own calibrated guide:

• Common langsat problems & fixes
• Langsat watering schedule
• Langsat light requirements
• Best soil mix for langsat
• Langsat fertilizing guide
• When to repot langsat
• How to propagate langsat
• How to prune langsat
• What's eating my langsat?
• Langsat growth rate & size
• Langsat cold hardiness
• Langsat temperature & humidity
• Is langsat toxic to cats & dogs?
• Is langsat toxic to cats?
• Is langsat toxic to dogs?

Featured in these plant shortlists

Langsat qualifies for 9 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best pet-safe houseplants — Houseplants the ASPCA lists as non-toxic to cats and dogs — every one verified against the ASPCA toxic and non-toxic plant list.
• Best plants for a north-facing window — Houseplants for a north-facing window: bright, even, indirect light and no scorching direct sun. Each pick verified against its documented light needs.
• Best drought-tolerant houseplants — Houseplants that prefer to dry out — forgiving of forgotten watering and ideal for travel or busy weeks.
• Best humidity-loving houseplants — Houseplants that thrive in a bathroom, kitchen, or by a humidifier — selected by documented humidity preference.
• Best pet-safe low-maintenance plants — Non-toxic to cats and dogs and forgiving of forgotten watering — the easiest safe choices for a busy pet household.
• Best pet-safe plants for bright light — Non-toxic to cats and dogs and happy in a bright, sunny spot — safe plants for your best-lit windowsill.
• Best pet-safe large indoor plants — Big, floor-standing houseplants the ASPCA lists as non-toxic to cats and dogs — a statement plant that is safe around pets.
• Best cat-safe plants — Houseplants the ASPCA lists as non-toxic to cats (and dogs) — safe greenery for a home with a curious cat.
• Best dog-safe plants — Houseplants the ASPCA lists as non-toxic to dogs (and cats) — safe greenery for a home with a curious dog.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Langsat is also known as Langsat, Duku, Longkong, and Lanzones.

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