Fertilising guide
How to fertilise Cushion Sandwort (Arenaria tetraquetra)— schedule & NPK
Also called Cushion Sandwort, Four-sided Sandwort.
More about cushion sandwort
About Cushion Sandwort
Arenaria tetraquetra · also called Cushion Sandwort, Four-sided Sandwort · flowering
Cushion Sandwort is a tight cushion-forming alpine perennial native to the mountains of Spain and southern France. It produces tiny white flowers in late spring above dense, compact mounds of overlapping leaves. A classic choice for alpine troughs, scree gardens, and rock crevices; demands perfect drainage and full sun to thrive.
Growth habit: Cushion-forming, densely compact perennial; extremely slow-growing
What fertiliser cushion sandwort actually wants — and why
Cushion Sandwort 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 cushion sandwort: 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 cushion sandwort, 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 cushion sandwort:
Minimal feeding; one very light application of a low-nitrogen granular fertiliser (e.g. 5-10-10) in early spring is sufficient. Rich soil destroys the tight cushion habit that makes this plant desirable. 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 cushion sandwort 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 cushion sandwort
Half strength is the safe default for cushion sandwort — 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 cushion sandwort first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the cushion sandwort watering schedule.
Signs you are over-feeding cushion sandwort
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for cushion sandwort:
- 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 cushion sandwort
- 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 cushion sandwort care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of cushion sandwort 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 cushion sandwort
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 cushion sandwort — frequently asked questions
What fertiliser does cushion sandwort 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. Cushion Sandwort 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 cushion sandwort?
Minimal feeding; one very light application of a low-nitrogen granular fertiliser (e.g. 5-10-10) in early spring is sufficient. Rich soil destroys the tight cushion habit that makes this plant desirable. Minimal feeding; one very light application of a low-nitrogen granular fertiliser (e.g. 5-10-10) in early spring is sufficient. Rich soil destroys the tight cushion habit that makes this plant desirable. 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 cushion sandwort?
Half strength is the safe default for cushion sandwort — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding cushion sandwort 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 cushion sandwort 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 cushion sandwort?
Flush the pot of cushion sandwort 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
- Cushion Sandwort care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water cushion sandwort — 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 nordmann fir
- How to fertilise noble fir
- How to fertilise korean fir
- All 8452 fertilising guides in the Growli library