Short answer
Water runs straight through when the mix has dried out, shrunk from the pot wall and turned water-repellent: water channels down the gap and out of the holes while the root ball stays dry. Water pools on top when the surface is crusted or compacted, the mix is too fine, or the drainage holes are blocked. Water slowly in 2–3 passes, or bottom-soak for 20–30 minutes. Grower practice, grounded in container physics.
Why
Peat and coco are easy to wet when moist and hard to wet when bone dry. Once dry, they shrink away from the wall and leave a channel [1].
Water takes the easy path down the channel and out, so you see runoff while the middle stays dry.
Pooling is the opposite problem: water can't get in. Fine, compacted mixes with too little air space drain slowly and stay saturated for days [1].
A pot that stays waterlogged starves roots of oxygen and favours Pythium root rot [2] and fungus gnat larvae [3]. So persistent pooling is worth fixing, not just waiting out.
The numbers
| Sign | Likely cause | Fix |
|---|---|---|
| Instant runoff, pot still light | Mix dried and shrunk from wall | Slow passes, or bottom-soak 20–30 min |
| Gap visible at the pot edge | Shrinkage | Press the edge down; water slowly |
| Water sits on top for minutes | Crust or compaction | Loosen top 1 cm; water slower |
| Pooling every time, heavy pot for days | Mix too dense | 20–35% perlite next run |
| Runoff never appears | Blocked holes or standing saucer | Clear holes; empty saucer within 30 min |
What to do
- Lift the pot after watering. Light means the water didn't stay; heavy means it did.
- For a dry pot, water a little over the whole surface, wait five minutes, and repeat 2–3 times.
- If that fails, stand the pot in 3–5 cm of pH-adjusted water for 20–30 minutes, then drain.
- For pooling, loosen the surface gently with a fork and clear the drainage holes.
- Next run, mix 20–35% perlite through the mix and don't let peat or coco dry out completely.
Common mistakes
- Reading runoff as proof the pot is wet.
- Letting coco dry out fully "to make roots search".
- Adding a gravel layer to fix pooling, instead of a better mix.
Related
- Full article: Drooping: overwatering vs underwatering
- Answers: how often to water · gravel in the bottom of pots · fabric vs plastic pots
- Terms: air-filled porosity · field capacity
