Giant Rhubarb
Gunnera manicata
Leaves on a scale nothing else in the border matches — but it wants boggy ground, three meters of room, and a covered crown in winter.
- Type
- Flower · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Sunlight
- Open sun or a little shade, either works.
- Watering
- Needs ground that stays constantly moist, even boggy.
- Feeding
- A generous annual feed of well-rotted manure.
- Frost tolerant
- Yes
- Flowering
- June
- Pruning
- Cut all the foliage down in late autumn.
- Overwintering
- The crown has to be protected from frost.
- Apr–Jun Spring Growth
- Jun–Jul Flowering
- Jul–Oct Growing
- Oct–Dec Leaf Fall
- Jan–Apr Leaf Fall
- Plant spacing
- 9 ft 10 in
- In-row spacing
- 9 ft 10 in
- Between rows
- 12 ft 4 in
- Square-foot density
- Not suited to SFG
- Root system
- A fleshy crown with thick perennial roots
- Working depth
- 12 in–3 ft
- Can reach
- 5 ft down where the soil allows
- Spread
- 10–15 ft across, about 1–1.5× the width of the plant
- Shallowest pot
- 18 in of soil
The crown is the plant’s bank account and it is slow to rebuild, which is why a new planting is left unpicked for a season or two. Plant it at the depth it asks for and no deeper; these rot from being buried far more often than they suffer from being shallow.
An enormous crown at the surface that will not take a hard frost, so the old leaves are folded over it in autumn as a blanket and left there until spring. It also drinks continuously, which is why it is a bog plant rather than a big perennial.
The habit is Giant Rhubarb’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- Slugs & snails Slugs on the shoots as they push through in spring
- Root & crown rot Crown rot when the winter covering is not enough
- Wind tearing at leaves that size
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Beneficial nematodes Steinernema & Heterorhabditis spp.Hunts Slugs & snails
Microscopic worms watered onto damp soil that hunt down soil-dwelling grubs and release a bacterium that kills them within days. Timing is the whole thing: warm, damp soil and a small target grub, which means late summer for most of what they are used against.
- Centipedes ChilopodaHunts Slugs & snails
Flat, fast, one pair of legs to a segment — and a predator, unlike the slow round millipede it is constantly confused with. It hunts slugs, cutworms, springtails and woodlice by night under mulch and stones. Learn the difference and leave this one alone.
- Frogs & toads AnuraHunts Slugs & snails
A resident toad works the beds every night for slugs, cutworms, and weevils. Recruit them with water — even a sunken basin pond — plus damp shade and an upturned-pot toad house; skip the slug pellets that poison their prey.
- Garden birds PasseriformesHunts Slugs & snails
Both things are true: birds strip your currants and a brood of blue tits takes several thousand caterpillars out of one fruit tree in a fortnight. Net what you must and welcome them everywhere else — a nest box near the apples is worth more than a spray.
- Ground beetle CarabidaeHunts Slugs & snails
Fast, glossy night hunters that patrol the soil surface for slugs, cutworms, and root-fly larvae. Give them daytime cover — thick perennial edges, stepping stones, a log — and skip the tillage that wrecks their burrows.
- Hedgehog Erinaceus europaeusHunts Slugs & snails
A European animal, and worth saying so plainly: there are no hedgehogs in North America, and the ally that does the same night shift here is the toad, the opossum or the ground beetle. Where they do occur, cut a gap in the fence and skip the pellets.
- Rove beetle StaphylinidaeHunts Slugs & snails
Slim, quick beetles with short wing cases that hunt in soil and litter, taking root-fly eggs and larvae, fungus-gnat larvae, and mites. Mulch and undisturbed ground keep them resident year-round.
- Salamanders & newts CaudataHunts Slugs & snails
Damp-loving hunters of slugs, worms, woodlice and beetle larvae that spend the day under a log or a stone and work the beds at night. Companions to the toads: they want the same damp shade, the same log pile, and the same absence of slug pellets.
- Snakes & lizards Colubridae & PhrynosomatidaeHunts Slugs & snails
A garter snake works the beds for slugs and voles and a fence lizard clears grasshoppers off a sunny wall. Almost every snake a gardener meets is harmless and useful; give them a log pile, a warm flat stone and a bit of cover and they stay.
Green-leaved flowers, like this one.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com