Why can adding too much fertiliser actually 'burn' and kill a plant?
Roots absorb water by osmosis, which flows from the dilute soil into the more concentrated root cells.
Roots absorb water by osmosis, which flows from the dilute soil into the more concentrated root cells. Dump in too much fertiliser and the soil solution becomes MORE concentrated than the root cells (hypertonic). Now osmosis reverses: water is drawn OUT of the roots into the soil, dehydrating the plant despite the soil looking moist — the classic 'fertiliser burn'. Moderate feeding keeps the gradient the right way round.
Key point
Excess fertiliser makes the soil hypertonic, so water leaves the roots by osmosis (exosmosis) and the plant dries out.
Common mistake
assuming more fertiliser always means faster growth.
Memory tip
too salty a soil pulls water OUT of roots — feed in moderation.
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