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Fertilising guide

How to fertilise Roundleaf Sundew (Drosera rotundifolia)— schedule & NPK

Also called Common sundew.

More about roundleaf sundew

About Roundleaf Sundew

Drosera rotundifolia · also called Common sundew · flowering

Drosera rotundifolia is the temperate roundleaf sundew native to acidic bogs across the Northern Hemisphere. Its flat rosette of round, long-stalked leaves bristles with red, dew-tipped tentacles that trap small insects. Fully cold-hardy, it forms a winter resting bud (hibernaculum) and demands a genuine cold dormancy, pure water, and permanently wet, acidic peat.

Growth habit: Low, flat rosette of round leaf blades on long stalks, each blade covered in red glandular tentacles; dies back to a tight winter hibernaculum.

What fertiliser roundleaf sundew actually wants — and why

Roundleaf Sundew is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.

For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for roundleaf sundew: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.

How often to feed roundleaf sundew, and which months

Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For roundleaf sundew:

Never fertilise the roots. It obtains nutrients from trapped midges and gnats; outdoors it feeds itself. Mineral feed will kill it. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

The dormant-season rule matters more than the exact interval: skip feeding entirely when roundleaf sundew is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.

What strength to mix for roundleaf sundew

Half strength is the safe default for roundleaf sundew — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

Feeding always goes onto already-damp soil, never dry roots — water roundleaf sundew first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the roundleaf sundew watering schedule.

Signs you are over-feeding roundleaf sundew

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for roundleaf sundew:

Signs you are under-feeding roundleaf sundew

If the symptoms point at watering, light or roots rather than nutrition, the full roundleaf sundew care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Flush the pot of roundleaf sundew with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

Organic vs synthetic feeds for roundleaf sundew

Organic options

A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.

Synthetic / liquid feeds

A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.

Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.

Fertilising roundleaf sundew — frequently asked questions

What fertiliser does roundleaf sundew need?

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Roundleaf Sundew is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

How often should I feed roundleaf sundew?

Never fertilise the roots. It obtains nutrients from trapped midges and gnats; outdoors it feeds itself. Mineral feed will kill it. Never fertilise the roots. It obtains nutrients from trapped midges and gnats; outdoors it feeds itself. Mineral feed will kill it. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

What strength of feed for roundleaf sundew?

Half strength is the safe default for roundleaf sundew — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

What does over-feeding roundleaf sundew look like?

Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding roundleaf sundew year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.

Should I flush the soil of roundleaf sundew?

Flush the pot of roundleaf sundew with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

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