Large round Corten steel pots for olive and other trees

We call a pot large when it measures at least 800 mm (31 in) across the opening. Three of our round models reach that size, all in 2 mm Corten steel: Callisto, a straight cylinder, from 800 to 1400 mm (31 to 55 in); Clio, a tapered pot with no rim, whose size reads top then bottom (800/600 means 800 mm at the top and 600 mm at the base), up to 1000 mm (39 in); and Calypso, a conical pot with a rim, up to 1000 mm (39 in). Each one comes 400, 600, 800 or 1000 mm high (16, 24, 31 or 39 in).

The soil volume is calculated from the outside dimensions, so it is a maximum: subtract the drainage layer and the space you leave below the rim for watering. For Calypso, whose narrower base is not specified, we give the volume of a cylinder of the same diameter, which the pot does not reach. Dimensions are in millimeters with inches rounded to the nearest inch, and prices are US prices in the base finish, our signature patina.

Size the pot for the plant it will grow into, not for the root ball that comes home from the nursery. Repotting out of a 1000 mm (39 in) pot means lifting hundreds of pounds of soil and roots, often well over 1,000 lb, so it makes sense to size up from day one. The figures below are a starting point: confirm the needs of a specific species with your nursery or garden center.

Height matters as much as width. A tree anchors better and handles wind better in 800 to 1000 mm (31 to 39 in) of soil; the 400 mm (16 in) formats suit shallow-rooted shrubs and wide, low plantings. For bamboo, choose a clumping variety, not a running one.

• Ø 800 mm (31 in), 600 to 800 mm (24 to 31 in) high, 300 to 400 L (79 to 106 US gal): a young olive, a citrus, a Japanese maple, tall ornamental grasses.
• Ø 1000 mm (39 in), 800 to 1000 mm (31 to 39 in) high, 500 to 785 L (132 to 207 US gal): an established olive, a larger maple, a small multi-trunk tree, a clump of bamboo.
• Ø 1200 to 1400 mm (47 to 55 in), up to 1540 L (407 US gal): a tree meant to stay in place for years, or a specimen with ground cover planted at its base.

Empty, a large pot weighs from 22.9 kg (50 lb) for Clio 800/700 × 400 mm to 96.7 kg (213 lb) for Callisto 1400 × 1000 mm; the soil is what changes everything. Depending on the mix and how wet it is, moist potting soil weighs roughly 1 to 1.8 kg per liter (about 8.3 to 15 lb per US gallon), and your soil supplier can give you the exact figure. A planted Callisto 1000 × 800 mm (39 × 31 in) therefore weighs well over 1,100 lb (half a metric ton), and a 1400 × 1000 mm (55 × 39 in) comes to roughly 3,600 to 6,300 lb, pot included. On a deck, a balcony or a rooftop, have a structural engineer or contractor check the load before you order.

Set the pot down empty and level, and fill it only once it is in its final spot: once planted, it will not be moved by hand again. Walk the route to the backyard ahead of time, because a 1200 or 1400 mm (47 or 55 in) pot will not fit through a standard front door or a narrow side gate. For a citrus that comes indoors for the winter, choose a smaller size or a rolling plant caddy rated for the load.

Before filling, find out where the water will leave the base: without a free outlet, hundreds of liters of soil stay waterlogged and the roots suffocate. Our product pages do not describe the base of every format, so ask us before you plant, and do not drill the steel without checking with us first. Our guide on how to choose a Corten steel planter covers the other decisions to make before you buy.

A 2 mm steel wall does not insulate: in winter, the mass of soil is what protects the roots, and the wider the pot, the longer the core of the root ball stays above freezing. In colder climates, choose species hardy for your zone, line the inside of the wall with an insulation that tolerates moisture before you fill, and mulch the surface.

Every pot arrives with the signature Cortenys patina, applied in our workshop. A large pot takes a lot of water, and the excess that runs down the outside carries oxide with it: plan a gravel bed, dark pavers or pot feet around and under it so the water can drain away. Our Corten care and rust stain guide explains how to deal with a mark.

The protective varnish offered as an option on Callisto, Clio and Calypso greatly reduces this runoff but does not rule it out: even varnished, a Corten steel pot can still stain the pavers, concrete or deck beneath it, so protect the ground in every case. On the large formats it adds a little to the price, for example $5,840 instead of $5,680 for Callisto 1000 × 800 mm (39 × 31 in).

For a medium-sized plant or a pair of pots flanking the front door, diameters of 350 to 600 mm (14 to 24 in) are enough: see our full range of round Corten steel planters.

If your space calls for a rectangular or square shape rather than a round one, our large Corten steel planters page covers the big boxes: troughs up to 2000 mm (79 in) long and squares such as Cybèle 2 mm, up to 1400 × 1400 mm (55 × 55 in). To ring a tree planted in the ground with steel, see our bottomless Corten steel planters. Near the ocean, powder-coated aluminum is the better choice (see our metal plant pots in Corten steel or aluminum), as our guide to Corten steel near the sea explains.