When and How to Repot Geraniums

Pelargoniums tolerate being slightly pot-bound — and many actually flower more freely when their roots are a little confined — but eventually they will outgrow their container and need potting on. Knowing when to repot and choosing the right pot size makes the difference between a plant that thrives and one that slowly declines.

Signs a geranium needs repotting

The most obvious sign is roots growing out of the drainage holes in the base of the pot. Other signs include the plant drying out very quickly after watering despite being watered thoroughly, slower-than-usual growth in the active growing season, or the plant becoming unstable in its pot. If you tip the plant out, a root-bound plant will show a dense mass of roots circling the outside of the root ball with very little compost visible. At this point, potting on is overdue.

Choosing the right pot size

The most common repotting mistake is going too large — choosing a pot several sizes bigger than the current one. Excess compost that has no roots growing into it stays wet for a long time and significantly increases the risk of root rot. Move up only one pot size at a time — typically 2–5cm wider in diameter. A pot 20–30cm in diameter suits most mature pelargoniums. Only pot on when the existing container is genuinely root-bound.

• Move up only one pot size at a time.
• Use free-draining compost with added grit or perlite.
• Best time to repot: late winter to early spring as growth starts.
• Water well after repotting and keep out of direct sun for a few days.

How to repot

Water the plant an hour before repotting to hydrate the roots. Remove the plant from its current pot by tipping it sideways and easing the root ball out. Gently tease out the outermost roots if they are heavily circling. Place crocks over the drainage holes of the new pot, add a layer of free-draining compost (multipurpose mixed with perlite or grit), position the plant at the same depth as before, and fill in around the root ball. Firm gently, water thoroughly, and allow to drain.

Refreshing compost without potting on

If a plant doesn't need a bigger pot but its compost has become tired and depleted after a full season, you can top-dress it instead. Gently scrape away the top 2–3cm of old compost without disturbing the roots, and replace with fresh compost. This refreshes the nutrient supply and improves compost structure without the disturbance of a full repot. It's particularly useful for overwintered pelargoniums that will go back outside in the same container.