Soil & potting mix
Best soil for Flame nasturtium (Tropaeolum speciosum)
Also called Flame nasturtium, Flame creeper, Scottish flame flower.
More about flame nasturtium
About Flame nasturtium
Tropaeolum speciosum · also called Flame nasturtium, Flame creeper · flowering
Flame nasturtium is a tuberous, herbaceous perennial climber native to the cool forests of Chile. Its brilliant scarlet flowers appear from midsummer to early autumn, followed by striking blue berries held in red calyces. It thrives in cool, moist gardens with its roots in shade and stems climbing into sun — a favourite for draping over dark evergreen hedges. RHS Award of Garden Merit holder.
Preferred mix: Moist, humus-rich, acid to neutral soil
Watch for — Failure to establish or return after winter: Most common in alkaline, dry, or south-facing warm soils; the tuber desiccates in summer heat — cool, acid, humus-rich soil with the root zone in shade is non-negotiable.
Why flame nasturtium needs this mix
Flame nasturtium is a Mediterranean dry-hillside plant — it wants a lean, sharply drained, slightly alkaline mix, and rots fast in rich, water-holding soil.
- Flame nasturtium evolved on stony, sun-baked slopes — its roots expect to dry out hard and quickly between rains, so the mix must drain almost as fast as you pour.
- A lean, low-nutrient mix keeps growth firm and aromatic; a rich one gives soft, sappy, flavourless growth that flops and rots.
- It tolerates and often prefers a slightly alkaline soil, the opposite of most houseplants.
For the full picture on what makes up a good mix, see our guide to the main types of soil and potting media — it explains why each ingredient above behaves the way it does.
What goes wrong with the wrong mix
The wrong soil is one of the most common reasons flame nasturtium struggles, and the damage often shows up weeks later as a watering problem. For this species specifically:
- Rich, moisture-holding compost is the classic killer of flame nasturtium — especially over a cold, wet winter, when the base of the plant simply rots.
- A peaty, acidic potting mix is doubly wrong: too wet and the wrong pH direction.
- No grit means the rootball stays damp for days, which a dry-climate root system never copes with.
Growing flame nasturtium in ordinary rich, moisture-retentive compost. Lean it out with at least a third grit, and never let it sit wet over winter.
pH — does it matter for flame nasturtium?
Flame nasturtium likes neutral to slightly alkaline soil, roughly pH 6.5-7.5. If your soil or compost is acidic, a little garden lime or extra grit nudges it the right way — the one common plant where you may add lime.
If you want to check or adjust it, the soil pH guide walks through testing and the safe ways to nudge a mix more acidic or more alkaline.
DIY mix vs a bagged one
Bagged "herb" or "Mediterranean" mixes are usually fine for flame nasturtium, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
Drainage and the pot
Sharp drainage is everything: a terracotta pot with a big hole, gritty mix and never a saucer left full. Raised beds suit these herbs outdoors for the same reason.
A gritty mix barely breaks down, so flame nasturtium needs little repotting — refresh the top layer and the grit every couple of years rather than potting on aggressively. When the time comes, our repotting guide for flame nasturtium covers the timing and technique step by step.
Flame nasturtium soil — frequently asked questions
What is the best soil mix for flame nasturtium?
2 parts standard peat-free compost or loam : 1 part coarse horticultural grit : 1 part perlite or coarse sand. Flame nasturtium evolved on stony, sun-baked slopes — its roots expect to dry out hard and quickly between rains, so the mix must drain almost as fast as you pour.
Can I use normal potting soil for flame nasturtium?
Rich, moisture-holding compost is the classic killer of flame nasturtium — especially over a cold, wet winter, when the base of the plant simply rots. Bagged "herb" or "Mediterranean" mixes are usually fine for flame nasturtium, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
Does flame nasturtium need a special pH?
Flame nasturtium likes neutral to slightly alkaline soil, roughly pH 6.5-7.5. If your soil or compost is acidic, a little garden lime or extra grit nudges it the right way — the one common plant where you may add lime.
Should I buy a bagged mix or make my own for flame nasturtium?
Bagged "herb" or "Mediterranean" mixes are usually fine for flame nasturtium, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
How often should I refresh the soil for flame nasturtium?
A gritty mix barely breaks down, so flame nasturtium needs little repotting — refresh the top layer and the grit every couple of years rather than potting on aggressively. Sharp drainage is everything: a terracotta pot with a big hole, gritty mix and never a saucer left full. Raised beds suit these herbs outdoors for the same reason.
Keep reading
- Flame nasturtium care — the full brief (light, water, humidity, problems, pet safety)
- How often to water flame nasturtium — the schedule the mix feeds into
- Repotting flame nasturtium — when and how to refresh the mix
- Soil pH guide — test it and adjust it safely
- Overwatered plant — signs and recovery
- Root rot — how the wrong soil starts it, and how to save the plant
- Should I water my plant? The simple check first
- Best soil for daphne cneorum
- Best soil for daphne x burkwoodii 'carol mackie'
- Best soil for fothergilla gardenii
- All 6887 soil and potting-mix guides in the Growli library