Fertilising guide
How to fertilise Free-flowering Streptocarpus (Streptocarpus floribundus)— schedule & NPK
Also called Free-flowering Streptocarpus, Kranskop Streptocarpus.
More about free-flowering streptocarpus
About Free-flowering Streptocarpus
Streptocarpus floribundus · also called Free-flowering Streptocarpus, Kranskop Streptocarpus · houseplant
Streptocarpus floribundus is a rare, threatened perennial herb native to the doleritic cliff faces of Kranskop in KwaZulu-Natal, South Africa, where it grows in cool, shaded, moist crevices. It produces masses of mauve-purple, tubular flowers — hence the species epithet floribundus, meaning 'flowering freely' — mainly in early summer. The most critical care requirement is avoiding overwatering, as this plant is extremely sensitive to waterlogged roots despite needing consistently moist conditions. Cape primrose (Streptocarpus) is listed by the ASPCA as non-toxic to cats and dogs.
Growth habit: Compact, stemless perennial herb with a basal rosette of soft, hairy, strap-like leaves; produces successive flushes of flowers on branching scapes from the leaf axils.
What fertiliser free-flowering streptocarpus actually wants — and why
Free-flowering Streptocarpus 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 free-flowering streptocarpus: 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 free-flowering streptocarpus, 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 free-flowering streptocarpus:
Feed with a high-potash liquid fertiliser (tomato feed type) at quarter-strength every two weeks during the flowering season; reduce to monthly at quarter-strength in winter. Treat that as monthly 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 free-flowering streptocarpus 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 free-flowering streptocarpus
Half strength is the safe default for free-flowering streptocarpus — 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 free-flowering streptocarpus first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the free-flowering streptocarpus watering schedule.
Signs you are over-feeding free-flowering streptocarpus
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for free-flowering streptocarpus:
- 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.
Signs you are under-feeding free-flowering streptocarpus
- Uniformly pale or yellow-green leaves, oldest first.
- Noticeably small new leaves and stalled growth in good light and season.
- A generally tired, lacklustre look despite correct watering and light.
If the symptoms point at watering, light or roots rather than nutrition, the full free-flowering streptocarpus care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of free-flowering streptocarpus 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 free-flowering streptocarpus
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 free-flowering streptocarpus — frequently asked questions
What fertiliser does free-flowering streptocarpus 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. Free-flowering Streptocarpus 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 free-flowering streptocarpus?
Feed with a high-potash liquid fertiliser (tomato feed type) at quarter-strength every two weeks during the flowering season; reduce to monthly at quarter-strength in winter. Feed with a high-potash liquid fertiliser (tomato feed type) at quarter-strength every two weeks during the flowering season; reduce to monthly at quarter-strength in winter. Treat that as monthly 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 free-flowering streptocarpus?
Half strength is the safe default for free-flowering streptocarpus — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding free-flowering streptocarpus 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 free-flowering streptocarpus 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 free-flowering streptocarpus?
Flush the pot of free-flowering streptocarpus 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.
Keep reading
- Free-flowering Streptocarpus care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water free-flowering streptocarpus — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise maranta 'massangeana'
- How to fertilise stromanthe triostar (tricolor)
- How to fertilise stromanthe 'multicolor'
- All 10153 fertilising guides in the Growli library