Hur du väljer rätt krukstorlek för dina inomhusväxter

A fiddle-leaf fig sits in a corner of a Stockholm apartment, its roots pressing hard against the walls of a pot two sizes too small, while three metres away a small succulent drowns slowly in a glazed vessel that holds water for weeks. Both plants were chosen carefully. Both are failing quietly. The problem is almost never the plant itself — it is the relationship between the root system, the growing medium and the container that surrounds them. Getting that relationship right is one of the most practical things a person can do for the greenery they bring indoors, and it requires less botanical expertise than it does patient attention to a handful of physical principles. This guide works through those principles in plain terms, with specific numbers and named plant families, so that the next choice made at the shelf feels grounded rather than guessed.

Reading the Root: How Pot Diameter and Depth Actually Work ¶

The standard advice — choose a pot one size up from the current one — is a useful shorthand, but it flattens a distinction that matters. Diameter and depth are separate decisions, and conflating them leads to the two most common indoor-plant mistakes: a container so wide that excess compost stays wet between waterings, and a container so shallow that tap roots double back on themselves and stall the plant's growth entirely.

For most leafy houseplants sold in Swedish garden centres and home stores — Monstera deliciosa, Ficus lyrata, Pothos varieties, Calathea — the working rule is that the pot's internal diameter should sit roughly 2 to 4 centimetres wider than the plant's current root ball, measured across its widest point. Going larger than that in a single step is tempting when a plant looks rootbound, but a dramatically oversized container holds far more moisture than young roots can draw up, and in the lower light levels of a Swedish November or February interior, that surplus moisture simply lingers. Root rot is almost always a function of poorly matched volume, not overwatering alone.

Depth is the dimension that gets less attention. Shallow-rooted plants — most Calathea, Peperomia, and African violets — thrive in pots where depth roughly equals diameter, or even slightly less. Tap-rooted plants and those that build substantial underground structure, such as Sansevieria trifasciata or Dracaena marginata, need a container at least as deep as it is wide, and ideally somewhat deeper. A 17-centimetre-diameter pot paired with only 12 centimetres of depth will arrest a Dracaena within a single growing season.

Terracotta or Glazed Stoneware: A Question of Climate and Rhythm ¶

Sweden's indoor climate presents a specific set of conditions that matter when choosing between unglazed terracotta and glazed stoneware. Central heating runs hard from October through April across most of the country, and the relative humidity inside a typical apartment in Gothenburg or Uppsala during those months can drop to 30 percent or below. That is dry enough to accelerate evaporation through the walls of an unglazed terracotta pot significantly, which changes the watering rhythm in ways most people do not anticipate when they bring a new container home.

Unglazed terracotta is breathable in a way that genuinely benefits plants prone to root rot — succulents, cacti, Aloe, and most Mediterranean herbs kept on a windowsill. The clay wicks moisture outward through its walls, and the roots experience a drying cycle between waterings that mimics their native habitat. In a warm, dry Swedish winter interior, a 14-centimetre terracotta pot holding a cactus may need watering only every three to four weeks. The same plant in a glazed stoneware container of identical size might need water once every six to eight weeks under the same conditions, because none of the moisture escapes laterally through the vessel walls.

Glazed stoneware is the more forgiving choice for moisture-loving plants — Ferns, Calathea, Maranta — precisely because it retains humidity within the growing medium. The glaze also makes the container easier to keep clean and prevents the white mineral deposits that form on terracotta surfaces in areas with hard water, which is common across much of eastern Sweden. The practical trade-off is that glazed containers demand more attentive drainage: a pot without a hole in the base, however beautiful, becomes a sump, and in a low-light Swedish winter interior there is rarely enough warmth or air movement to compensate.

The clay or the glaze is not decoration — it is part of the drainage system.

A Short Checklist Before You Choose a New Pot ¶

Before settling on a container, it helps to work through a small set of questions in sequence. These are not abstract considerations — each one points to a measurable or observable characteristic of the plant or the space.

• Measure the current root ball's diameter and add 2 to 4 centimetres — that is the target internal diameter for the new pot.
• Identify whether the plant is shallow-rooted (Calathea, Peperomia) or deep-rooted (Dracaena, Sansevieria) and choose depth accordingly.
• Check whether the container has a drainage hole — if not, it should be used only with a gritty, fast-draining substrate and very measured watering.
• Consider the season: repotting in March or April, as Swedish daylight begins to lengthen past 12 hours, gives roots time to establish before summer growth.
• Match material to plant type — terracotta for drought-tolerant species, glazed stoneware for moisture-loving tropicals.
• Account for placement: a radiator nearby will accelerate drying in terracotta pots and can stress moisture-sensitive plants in any material.

At Växthemmet, the people behind the shelves spend a good deal of time thinking through exactly these questions — which containers suit which plants, and which combinations make sense for the homes and light conditions particular to life in Sweden. Anyone working through a repotting decision or building a collection from scratch is welcome to come in and talk it through in person.