Gunnera manicata (Giant Rhubarb) care

Light

In the wild gunnera manicata grows on the bright edge of a forest canopy, not in the canopy and not in the open. Indoors, that translates to within a metre of an unobstructed window, sheer curtain optional. Full sun to partial shade in a sheltered spot. It needs good light to drive its huge leaves but appreciates protection from scorching midday sun and, crucially, from drying or cold winds that shred the foliage. The fastest test: a hand held at the leaf casts a soft-edged shadow at noon — sharp shadow means too much sun, no shadow means too little light.

Watering

Aim for keep permanently wet; never let the rootzone dry for gunnera manicata, but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. A bog and streamside plant with a vast appetite for water to support its enormous leaves. Grow in constantly moist to wet ground beside water; even brief drought causes the leaves to wilt and collapse dramatically.

Soil and pot

Gunnera manicata grows best in deep, rich, permanently moist loam. Demands a deep, fertile, humus-rich soil that never dries, ideally at a pond or stream margin. Incorporate generous organic matter. It is a heavy feeder and grows largest in boggy, nutrient-rich ground. 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

Gunnera manicata sits happiest at around 60-100% humidity and 5-28°C (41-82°F). An outdoor waterside plant that thrives in the high humidity of sheltered, damp gardens. Humid, still air keeps its giant leaves intact; hot, dry or windy air causes scorch and tearing. If you keep the room above 5 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 gunnera manicata sparingly. A hungry plant: mulch generously each spring with well-rotted manure or rich compost, which both feeds it and conserves moisture. A balanced general fertiliser in early growth supports the huge leaves. Feeding is well rewarded by leaf size in this gross feeder. 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 gunnera manicata in the Growli community. Each is annotated with the most common cause so you know where to start.

• Winter cold damage — The crown is frost-tender. In cold-winter areas fold the dying leaves over the crown or mulch heavily to insulate it; unprotected crowns can be killed in hard frosts.
• Drought collapse — If the soil dries, the enormous leaves wilt and brown rapidly. Permanent moisture at the roots is essential; site it where water is guaranteed.
• Wind scorch and tearing — Exposed leaves are shredded and browned by wind and harsh sun. Plant in a sheltered position to keep the foliage whole and handsome.
• Prickly handling and overcrowding — Leaf stalks bear sharp prickles, so wear gloves when working around it; its sheer size can also overwhelm smaller plantings, so allow ample space from the start.

Propagation

Propagate by division in spring, cutting rooted sections from the crown with a sharp spade, or from seed sown fresh on the surface of moist compost and kept warm. Division of established crowns is the more reliable method for gardeners. 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

Gunnera manicata is mildly toxic to pets. Gunnera manicata is not individually listed on the ASPCA Toxic and Non-Toxic Plant lists; despite the common name it is unrelated to true rhubarb (Rheum, which the ASPCA does list as toxic). Its pet status is unconfirmed, so treat it with caution and verify with a vet rather than assuming it is safe. 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.

Gunnera manicata deep-dive guides

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

• Gunnera manicata watering schedule
• Gunnera manicata light requirements
• Best soil mix for gunnera manicata
• Gunnera manicata fertilizing guide
• When to repot gunnera manicata
• How to propagate gunnera manicata
• Gunnera manicata growth rate & size
• Gunnera manicata cold hardiness
• Gunnera manicata temperature & humidity
• Is gunnera manicata toxic to cats & dogs?
• Is gunnera manicata toxic to cats?
• Is gunnera manicata toxic to dogs?
• Getting gunnera manicata to bloom

Featured in these plant shortlists

Gunnera manicata qualifies for 5 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• 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 flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Best houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Gunnera manicata is also known as Giant Rhubarb, Brazilian Giant Rhubarb, and Prickly Rhubarb.

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