Fertilising guide

How to fertilise Achimenes (Achimenes longiflora)— schedule & NPK

Also called hot water plant, Achimenes, widow's tears.

More about achimenes

About Achimenes

Achimenes longiflora · also called hot water plant, Achimenes · flowering

Achimenes longiflora, the hot water plant, is a tropical rhizomatous gesneriad that explodes into violet-blue, trumpet-shaped flowers all summer above soft, hairy leaves. A relative of the African violet, it grows from tiny scaly rhizomes, blooms profusely in warmth and bright indirect light, then dies back to overwinter dormant. Steady warmth and even moisture are key, as a check in growth can stall flowering entirely.

Growth habit: Bushy to trailing rhizomatous perennial with slender stems and soft hairy leaves, suiting pots, baskets and edging. Grows each spring from small scaly rhizomes and dies back completely to them each winter.

Watch for — Leaf scorch and spotting: Direct sun burns the soft leaves, and cold droplets on the hairy foliage leave pale marks. Filter strong light and water at the soil with tepid water.

What fertiliser achimenes actually wants — and why

Achimenes is feeding to flower, not to grow leaves — it needs a higher-phosphorus / specialist bloom feed, given little and often, to set and hold its display.

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 achimenes: 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 achimenes, 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 achimenes:

Feed every 1-2 weeks once growth is established and through flowering, using a balanced or high-potassium fertiliser at half strength, or an African violet feed. Stop feeding as the plant begins to die back in late summer and through dormancy. The pattern that matters: feed little and often through active growth and budding — every 1-2 weeks — and ease right off during the rest period that triggers the next flush.

The dormant-season rule matters more than the exact interval: skip feeding entirely when achimenes 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 achimenes

Very dilute — quarter strength, the classic "weakly, weekly" approach for achimenes. These plants have fine roots that scorch easily and a steady trickle beats an occasional strong dose for flowering.

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

Signs you are over-feeding achimenes

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

Lush green leaves but few or no flowers (too much nitrogen).
Brown, scorched leaf tips and edges — a classic fine-root burn.
White salt crust on the medium or pot, and stalled buds.
Bud blast: buds forming then shrivelling and dropping.

Signs you are under-feeding achimenes

Sparse or no flowering despite good light and the right season.
Smaller, paler new leaves and a generally weak, tired plant.
Flowers that are smaller or fade faster than they should.

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

Flushing and leaching the salts

Specialist and bloom feeds leave salts that scorch fine roots — flush achimenes thoroughly with plain water until it runs clear every 4-6 weeks in the feeding season, and always between feeds for orchids.

Organic vs synthetic feeds for achimenes

Organic options

Gentler options exist: a dilute seaweed feed (mildly potassium-rich) or worm-casting tea. UK: Westland seaweed, or a dilute tomato feed like Tomorite for bud-formers; US: Espoma Orchid! / Violet! or Neptune's Harvest. Lower burn risk, slower response.

Synthetic / liquid feeds

A species-matched bloom feed at quarter strength — UK: Baby Bio Orchid / African Violet food, or a high-potash Tomorite/Phostrogen for budding bloomers; US: Miracle-Gro Orchid or Bloom Booster, Schultz African Violet.

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 achimenes — frequently asked questions

What fertiliser does achimenes need?

A higher-phosphorus "bloom" formula or a species-specific feed (orchid food, African violet food, or a tomato-style high-potash/phosphorus liquid). A high-nitrogen general feed gives you lush leaves and almost no flowers. Achimenes is feeding to flower, not to grow leaves — it needs a higher-phosphorus / specialist bloom feed, given little and often, to set and hold its display.

How often should I feed achimenes?

Feed every 1-2 weeks once growth is established and through flowering, using a balanced or high-potassium fertiliser at half strength, or an African violet feed. Stop feeding as the plant begins to die back in late summer and through dormancy. Feed every 1-2 weeks once growth is established and through flowering, using a balanced or high-potassium fertiliser at half strength, or an African violet feed. Stop feeding as the plant begins to die back in late summer and through dormancy. The pattern that matters: feed little and often through active growth and budding — every 1-2 weeks — and ease right off during the rest period that triggers the next flush.

What strength of feed for achimenes?

What does over-feeding achimenes look like?

Lush green leaves but few or no flowers (too much nitrogen). Brown, scorched leaf tips and edges — a classic fine-root burn. White salt crust on the medium or pot, and stalled buds. Bud blast: buds forming then shrivelling and dropping. Using an ordinary high-nitrogen houseplant feed on achimenes is the headline mistake — you get a healthy-looking plant that simply refuses to bloom. The second is feeding through the rest period and breaking the dormancy cue it needs to set buds.

Should I flush the soil of achimenes?