Large Corten steel planters

Outside dimensions, the empty weight given on each product page, and the UK price in the base finish (our signature patina). The outside volume (L × W × H in dm³) is a guide to scale: the soil you can actually put in is slightly less.

In a large planter, the weight is in the soil, not the steel. Depending on the mix and how recently it has rained, moist compost weighs roughly 1 to 1.8 kg per litre; your soil supplier can give you the exact figure. Filled to the brim, that gives these rough figures:

• Cybèle 2 mm, 1000 × 1000 × 400 mm: 400 L, so roughly 400 to 720 kg of soil, plus 43.3 kg of steel.
• Déméter 2 mm, 2000 × 500 × 1000 mm: 1000 L, so roughly 1 to 1.8 tonnes of soil, plus 106.2 kg of steel.
• Cybèle or Thalie, 1400 × 1400 × 1000 mm: 1960 L, so roughly 2 to 3.5 tonnes of soil, before the plants and the water the soil holds.

On a concrete patio or straight on the lawn, these weights are mainly a question of handling. On a roof terrace, a balcony or decking raised on pedestals, they become a structural question: a large planter, once filled, can weigh more than a tonne on a footprint of less than 2 m². Only a structural engineer or builder who knows the building can say whether the load is acceptable. Give them the outside dimensions, the empty weight and the estimated soil volume of the format you have in mind.

If weight is the obstacle, reduce the height before the footprint. On the same square, going from 1000 to 600 mm high takes away 40% of the volume, and many plants do not need that depth. Maïa, at 300 mm high, covers 1200 × 1200 mm with 432 L, split into compartments that suit herbs, grasses and seasonal planting on a roof terrace.

Before you order a 1400 mm square or a 2000 mm trough, measure every gate, side return, doorway, step and tight corner on the way to its final spot. The planter has to be carried in empty, and already weighs 37.5 to 124.1 kg depending on the format: allow two to four people to lift it. In a terraced house with no side access, check the hallway and the back door as carefully as the garden itself.

Once the planter is in place, check that it sits level: the soil comes afterwards, because a filled planter will not be moved again. For a large volume, a drainage layer at the bottom, a filter fabric over it and then compost added in successive layers limit settling; water between layers. Our guide on how to choose a Corten steel planter covers the other points to decide before you buy.

The large squares, from 1000 to 1400 mm, take a small tree (an olive, a Japanese maple, a multi-stemmed tree) with ground cover at its feet. The long Déméter troughs, 2000 mm by 500 or 600 mm wide, carry a screening hedge of evergreen shrubs or clump-forming bamboo, a useful line between a patio and the neighbours. Leave a few centimetres below the rim so that watering does not spill over. For a single tree in a round pot rather than a box, see our large Corten steel pots: Callisto, Clio and Calypso from Ø 800 mm.

For more planting ideas around steel, from borders to terraces, see our Corten steel garden ideas.

A large planter has a large wall area, so in a wet winter more rainwater runs down the steel while the patina is still forming. On pale stone or a light patio, stand it on spacers or on a strip of gravel, as our Corten care and rust stain guide explains.

Every model on this page is also offered with our protective varnish, for example £990 for Déméter 2 mm in 1500 × 400 × 400 mm or £1,040 for Cybèle 2 mm in 1000 × 1000 × 400 mm. The varnish greatly reduces run-off, but even varnished, Corten steel can still stain the floor: keep the spacers, a gravel strip or a dark slab under a large planter in either finish.

In a garden, a large volume standing on open ground does not always need a base: our bottomless Corten steel planters let roots go down into the soil and save you buying and carrying tonnes of compost. On a patio or a roof terrace, keep a planter with a base.

If a long, narrow line suits your space better, see our Corten trough planters; for a single tree, our square Corten planters. For every size, go back to the full range of Corten steel planters.