Fertilising guide
How to fertilise Rumberry (Myrciaria floribunda)— schedule & NPK
Also called Guavaberry, Murta, Cainitillo.
More about rumberry
About Rumberry
Myrciaria floribunda · also called Guavaberry, Murta · edible
Rumberry is a slow-growing Caribbean and Central American tree in the Myrtaceae family, producing small, dark-purple to black fruits with a spicy, aromatic flavour — the traditional base of St Croix and Virgin Islands guavaberry liqueur. It prefers well-drained, slightly acidic soil and tolerates dry spells once established. Not known to be toxic to pets.
Growth habit: Slow-growing evergreen multi-stemmed tree or large shrub
What fertiliser rumberry actually wants — and why
Rumberry is an acid-loving plant — it can only take up nutrients in acidic soil, so the feed itself matters less than using an ericaceous formula and never liming.
An ericaceous (acidic) fertiliser, formulated to keep the soil pH low and supply iron and trace elements in a form acid-loving roots can absorb. Ordinary feeds and any lime lock out iron and yellow the leaves.
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 rumberry: 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 rumberry, 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 rumberry:
Apply a balanced slow-release granular fertiliser in spring and again in midsummer. A light application of sulphate of potash in late summer encourages fruit ripening. Avoid high-nitrogen feeds on mature fruiting trees. In practice: an ericaceous feed in spring as growth resumes, repeated through the main growing months; never apply lime, bonemeal or wood ash, which raise pH.
The dormant-season rule matters more than the exact interval: skip feeding entirely when rumberry 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 rumberry
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for rumberry. The variable that actually matters is pH, not concentration.
Feeding always goes onto already-damp soil, never dry roots — water rumberry first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the rumberry watering schedule.
Signs you are over-feeding rumberry
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for rumberry:
- Brown, scorched leaf margins from too strong or too frequent a dose.
- White salt crust on the soil surface.
- Soft, lush growth that fruits or flowers poorly.
Signs you are under-feeding rumberry
- Yellowing leaves with green veins (iron chlorosis from high pH).
- Weak growth, poor cropping and an overall pale, stressed look.
- Stunted new shoots in spring despite adequate water and light.
If the symptoms point at watering, light or roots rather than nutrition, the full rumberry care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush rumberry with rainwater (not hard tap water, which raises pH) if salts build up; better still, mulch with pine needles or composted bark and water with rainwater to hold the acidity.
Organic vs synthetic feeds for rumberry
Organic options
Composted pine bark, pine-needle mulch, used coffee grounds and an organic ericaceous feed gently maintain acidity. UK: Vitax or Westland Ericaceous; US: Espoma Holly-tone or Dr. Earth Acid Lovers. Slow, soil-improving, hard to overdo.
Synthetic / liquid feeds
A liquid or granular ericaceous feed — UK: Miracle-Gro Ericaceous, Vitax or Westland; US: Miracle-Gro Acid-Loving Plant Food or Espoma Holly-tone. Pair with rainwater and an acidic mulch for it to work.
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 rumberry — frequently asked questions
What fertiliser does rumberry need?
An ericaceous (acidic) fertiliser, formulated to keep the soil pH low and supply iron and trace elements in a form acid-loving roots can absorb. Ordinary feeds and any lime lock out iron and yellow the leaves. Rumberry is an acid-loving plant — it can only take up nutrients in acidic soil, so the feed itself matters less than using an ericaceous formula and never liming.
How often should I feed rumberry?
Apply a balanced slow-release granular fertiliser in spring and again in midsummer. A light application of sulphate of potash in late summer encourages fruit ripening. Avoid high-nitrogen feeds on mature fruiting trees. Apply a balanced slow-release granular fertiliser in spring and again in midsummer. A light application of sulphate of potash in late summer encourages fruit ripening. Avoid high-nitrogen feeds on mature fruiting trees. In practice: an ericaceous feed in spring as growth resumes, repeated through the main growing months; never apply lime, bonemeal or wood ash, which raise pH.
What strength of feed for rumberry?
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for rumberry. The variable that actually matters is pH, not concentration.
What does over-feeding rumberry look like?
Brown, scorched leaf margins from too strong or too frequent a dose. White salt crust on the soil surface. Soft, lush growth that fruits or flowers poorly. Feeding rumberry an ordinary fertiliser, or growing it in hard tap water / limey soil, is the defining mistake — it triggers lime-induced chlorosis (yellow leaves, green veins) no amount of feeding fixes until the pH comes down.
Should I flush the soil of rumberry?
Flush rumberry with rainwater (not hard tap water, which raises pH) if salts build up; better still, mulch with pine needles or composted bark and water with rainwater to hold the acidity.
Keep reading
- Rumberry care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water rumberry — 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 daikon 'tokinashi'
- How to fertilise korean radish 'altari'
- How to fertilise rattail radish
- All 11687 fertilising guides in the Growli library