Repotting is one of those tasks that plant people either obsess over or avoid entirely. Both extremes cause problems. Repot too often and you stress your plants unnecessarily, disrupt their root systems, and risk root rot from too much unused soil. Never repot and your plants eventually become so rootbound they stop growing, can’t absorb water properly, and slowly decline.

The sweet spot is knowing when a plant actually needs repotting and doing it carefully when the time comes. After killing a few plants through repotting mistakes in my early days of balcony gardening in Melbourne, I’ve learned to read the signs.

When to Repot

Roots circling the bottom of the pot or growing through drainage holes. This is the clearest sign. When you lift the plant out and see a dense mat of roots wrapping around the root ball rather than growing outward into soil, it’s time.

Water runs straight through the pot without being absorbed. When the root ball is so dense that water channels around it rather than soaking in, the plant can’t access moisture properly. You water, the water pours out the bottom, and the root zone stays dry.

Growth has slowed significantly despite good light and feeding. A rootbound plant diverts energy from leaf production to root maintenance. If your previously vigorous grower has stalled out and you’ve ruled out light and feeding issues, check the roots.

The plant is literally pushing itself out of the pot. Some plants — peace lilies and spider plants are notorious for this — grow with such vigour that they push their root mass upward, lifting the plant above the pot rim.

The soil has broken down and become compacted. Potting mix degrades over time. After 2-3 years, it loses structure, compacts, and doesn’t drain well. Even if the roots aren’t crowded, old soil needs refreshing.

When NOT to Repot

During winter. Most houseplants are dormant or growing very slowly in winter. Repotting when the plant can’t actively grow new roots to establish itself in the new pot creates stress. Wait until spring.

When the plant is flowering. Repotting diverts energy away from flowers. Enjoy the blooms first, then repot after flowering finishes.

Within the first few weeks of bringing a new plant home. The plant is already adjusting to new light, humidity, and temperature conditions. Adding a repotting disruption on top of that is asking for trouble. Let it settle for at least a month.

Just because you bought a pretty new pot. I get it — but if the plant doesn’t need repotting, leave it be. You can always slip the current pot inside a decorative cachepot instead.

Choosing the Right Pot Size

This is where most people go wrong. The instinct is to give the plant lots of room to grow, so you move it from a 15cm pot to a 25cm pot. Bad idea.

Go up by one size — about 2-5cm larger in diameter. That’s it. A plant in a 15cm pot goes into a 17-20cm pot.

Why? Excess soil holds moisture the roots haven’t grown into yet. That moisture sits there, stays wet, and creates conditions for root rot. According to advice from the Royal Botanic Gardens Melbourne, gradually increasing pot size is one of the most important factors in successful repotting.

The only exception is very fast growers like pothos, philodendrons, and monstera during their peak growing season. These can handle a slightly larger jump — maybe 5-7cm — because they’ll fill the new pot quickly.

The Actual Repotting Process

What you need:

• New pot with drainage holes (non-negotiable)
• Fresh potting mix appropriate for the plant type
• Watering can
• Newspaper or tarp to catch mess (balcony gardening gets messy fast)

Step by step:

1. Water the plant a day before repotting. Moist soil holds together better, and hydrated roots are more flexible and less likely to snap during handling.

2. Remove the plant from the old pot. Squeeze the sides of a plastic pot to loosen the root ball. For ceramic pots, run a butter knife around the inside edge. Turn the pot upside down and gently tap the bottom. The plant should slide out. Never yank on the stem.

3. Inspect the roots. Healthy roots are white or light tan and firm. Dark, mushy, or smelly roots are rotting — trim them off with clean scissors. If the root ball is tightly wound, gently tease apart the outer roots with your fingers. You’re not trying to demolish the root ball, just loosen the outer layer so roots can grow outward into fresh soil.

4. Add fresh potting mix to the new pot. Put enough in the bottom so the plant will sit at the same depth it was in the old pot — not deeper. The base of the stem should be at or slightly below the pot rim, not buried.

5. Place the plant and fill around it. Hold the plant centered in the pot and fill around the root ball with fresh mix. Firm the soil gently with your fingers — not packed tight, just settled enough to hold the plant upright. Leave about 2cm of space between the soil surface and pot rim for watering.

6. Water thoroughly. Water until it runs freely from the drainage holes. This settles the soil, hydrates the roots, and eliminates air pockets. The soil level will drop slightly after watering — that’s normal.

7. Don’t fertilise for 2-3 weeks. Fresh potting mix usually contains slow-release fertiliser. Adding more on top of freshly disturbed roots can cause fertiliser burn. Give the plant time to recover before you start feeding.

Post-Repotting Care

Expect some sulking. Even with perfect technique, repotting disrupts roots and stresses the plant. It’s completely normal for a freshly repotted plant to drop a leaf or two, wilt slightly, or slow its growth for a few weeks.

Keep the plant in its usual spot — don’t move it to a brighter or dimmer location at the same time. Maintain normal watering but be cautious about overwatering while roots are establishing. The new soil retains moisture differently than the old, broken-down mix.

I’ve noticed my plants on the balcony handle repotting better in early spring (September-October in Melbourne) when they’re just starting to push new growth. The timing means they’re primed to grow into the new soil rather than just sitting in it. Working with a group that does AI strategy support taught me to think about timing and sequencing in systems — and honestly, plant care is a system. Everything connects.

Special Cases

Orchids: Repot into orchid bark, not regular potting mix. Their roots need air. Repot after flowering, usually every 1-2 years.

Cacti and succulents: Use a fast-draining cactus mix. Don’t water for a week after repotting — let any root damage heal first to prevent rot.

Very large plants: If repotting is impractical (say, a huge fiddle leaf fig in a heavy pot), top-dress instead. Scrape off the top 3-5cm of old soil and replace with fresh mix. This refreshes nutrients without disturbing roots.

Repotting isn’t complicated. The plants that die from repotting almost always die from one of three things: a pot that’s too large, repotting at the wrong time of year, or overwatering afterwards. Avoid those three mistakes and your success rate will be very high.