Syzygium jambos

Rose apple (Syzygium jambos; also Malabar plum, pomarrosa, jambu mawar, yambo) is a Southeast Asian myrtle-family tree grown for its showy rose-scented flowers and crisp, aromatic fruit. The fruit is hollow, with 1 to 4 seeds rattling loose in the center, and so perishable it rarely makes it to market. Native to Malaya and the East Indies, naturalized across the tropics, and small enough to fruit in a large container.

Ripe fruit on the branch. PMATAS, CC BY-SA 4.0, via Wikimedia Commons

Rose apple (Syzygium jambos)
Scientific name	Syzygium jambos (L.) Alston
Family	Myrtaceae
Fruit type	Fleshy berry
Growth form	Evergreen tree
USDA zones	9 to 11. Zone 9 requires protection when young. Frost-free or near-frost-free sites are best.
Frost tolerance	Young trees are frost-tender. Mature trees survive brief dips to about -3 °C (26 °F). Regular freezes mean no fruit.
Mature height	7.5 to 12 m (25 to 40 ft) in ground
Mature width	Crown often wider than it is tall
Container	Yes. Fruits reliably in pots. Can be held to 2 to 3 m with pruning.
Growth rate	Slow as seedlings, speeds up once established
Soil	Not fussy. Deep loam is ideal, but it grows on sand and limestone. Very tolerant of wet feet.
Water	Likes moisture. Tolerates semi-arid conditions but prolonged dry spells hurt it. 700 to 4,000 mm/yr.
Sun	Full sun once established. Young trees want partial shade.
Germination	10 to 120 days from fresh seed. No dormancy. Seeds are recalcitrant and die if dried.
Stratification	Not required
Years to fruit	About 3 to 4 years from seed. Air-layers fruit sooner.
Pollination	Self-fertile. Bees and other insects do the work.
Yield	Modest. About 2 kg (5 lbs) per mature tree per season. Fruit is hollow and very light.
Harvest	Native SE Asia: dry-season bloom, fruit early in the wet season. Near the equator, sporadic almost year-round.

Flowers are cream-colored stamen puffs in terminal clusters, sweetly scented. Ajtjohnsingh, CC BY-SA 4.0, via Wikimedia Commons

Identification

Don't trust the common name. "Rose apple" gets slapped on a pile of Syzygium species. S. jambos is the one with:

• Lanceolate leaves 10 to 22 cm long, opposite, new flush rosy pink
• Big creamy-white flower puffs 5 to 10 cm across, made almost entirely of about 300 stamens
• Nearly round to slightly pear-shaped fruit, 4 to 5 cm, pale yellow to whitish skin, often pink-blushed, loose seeds rattling in a hollow center
• Rosewater scent when you rub or bite a ripe fruit

Most often confused with:

• Wax apple (S. samarangense): larger, glossy red or pink bell-shaped fruit, no rose scent
• Malay apple (S. malaccense): much bigger, deep red fruit
• Java plum (S. cumini): dark purple, astringent
• Watery rose apple (S. aqueum): pear-shaped, without the rose aroma

If it smells like rosewater, it's this one.

New foliage flushes rosy pink before maturing to glossy dark green. Tonton Bernardo, CC BY-SA 3.0, via Wikimedia Commons

Climate and site

A true tropical that pushes into warm subtropics. USDA zones 9 to 11, but zone 9 is marginal. The tree will survive with protection, but regular freezes mean no fruit. At the climatic limit (coastal California, San Francisco) it grows lush and sets nothing. It flourishes in daytime temps of 18 to 38 °C, tolerating 5 to 40 °C, and grows from sea level to about 1,200 m in the tropics (2,300 m in Ecuador). Above that it won't fruit.

Give it moisture. It's a stream-bank tree in the wild and one of the most water-tolerant fruit trees you can plant. It shrugs off semi-arid conditions too, but extended dry spells knock it around. Prefers 1,200 to 1,600 mm annual rainfall. Moderately wind-resistant, tolerates seaside conditions, but is not highly salt-tolerant. Don't plant it in direct salt-spray exposure. Young trees need partial shade and transplant badly, so pot them up early and plant out small.

Container growing

Rose apple is one of the better tropical fruits for container culture. It's compact and bushy, fruits reliably in pots, and can be held to 2 to 3 m with pruning. That makes it a good candidate for zone pushers who need to move it under cover for winter.

• Pot size: Start in a 5-gallon, work up to 15 to 25 gallon as the tree matures. Well-drained potting mix with some perlite or pumice.
• Water: Keep evenly moist. Don't let it dry out, but don't let it sit in water. Container trees dry out faster than in-ground.
• Fertilizer: 2 to 3 times per year with a complete fertilizer including micronutrients. On high-pH soil or hard water, watch for micronutrient deficiencies and use foliar sprays.
• Light: Full sun once established. Young plants want some shade. In marginal zones, maximize sun exposure and heat.
• Overwintering: Zone 8 and 9 growers can keep a container tree in a greenhouse or bring it inside during freezes. It needs warmth to fruit. A cool, dark winter will keep it alive but unproductive.
• Pruning: Takes hard pruning well (used as a living fence in Guatemala). Prune to shape and control size. It coppices readily.

Zone pushing

For growers in zones 8 and 9 trying to push the envelope:

• Mature trees survive brief dips to -3 °C (26 °F), but young trees need protection. Cover and mulch heavily when frost threatens.
• Regular freezes kill fruiting. If you get frost every winter, expect an ornamental, not a fruit tree.
• South-facing walls, frost pockets avoided, and overhead canopy cover can buy a few degrees of cold protection in-ground.
• Container culture with winter protection is the most reliable strategy in marginal zones. The tree fruits fine in a pot and comes inside for the cold snaps.
• Coastal California experience: the tree grows vigorously but won't set fruit at the cool margin. Heat accumulation matters for flowering and fruit set.

Propagation

• Seed is the standard method. Seeds are recalcitrant: no dormancy, viability measured in days, so sow fresh within days of cleaning. Germination takes 10 to 120 days. Seeds are polyembryonic, meaning one seed can throw 3 to 8 seedlings, most true to type. Surface-sow in shade, firm in, keep moist. Young plants transplant badly, so pot up individually before roots get large.
• Air-layering is the reliable clonal route. Spring layers treated with 1000 ppm NAA root about 60%. They won't root during the rainy season. West Bengal growers layer in July and plant out in October to November.
• Cuttings and grafting are mostly a bust. Hardwood cuttings don't root even with hormones. Semihard wood gives about 20%. Chip and T-budding don't take. Veneer grafting of spring-flush scions on 1-year-old rootstock succeeded in only about 31% of plants.

In India, vegetative propagation work has focused on selecting and fixing dwarf types, which is relevant for container growers looking for compact selections.

Flowering, fruiting and harvest

Fruit cut open showing the loose seeds in the hollow center. JonRichfield, CC BY-SA 3.0, via Wikimedia Commons

Self-fertile. Bees and insects do the work. Flowers are produced on new growth, late winter through spring and early summer in the subtropics, and sporadically through the year in the deep tropics. Often the tree will have fruit maturing while still producing more flowers.

In the native Southeast Asian range the calendar follows the rains. Bloom comes in the dry season, and fruit follows 8 to 12 weeks later, early in the wet season. Regional examples:

• South India: blooms January, ripe March to April
• Central India: blooms February to April, ripe June to July
• Jamaica and Puerto Rico: sporadic nearly year-round, a bit less in summer
• Florida and Bahamas: main crop May to July

Fruit is non-climacteric. It only gets better on the tree, so pick at full color. It bruises easily and goes downhill fast, which is why it never shows up in markets. Expect modest crops. A mature tree in India yields only about 2 kg a season.

Fruit and uses

Best eaten fresh off the tree, crisp and cold if you can manage it. Mostly skin and crisp flesh around a hollow core, light and refreshing with a rosewater scent. Some describe the flavor as a cross between apple and watermelon with a mild rose aftertaste. Beyond fresh:

• Jam or jelly (add lemon juice, the flavor is delicate)
• Syrup for cold drinks
• Stewed with sugar as dessert
• Candied halved fruit the Jamaican way (stewed in heavy sugar syrup with cinnamon)
• Stuffed and baked (halved, filled with sweet or savory filling, baked about 20 min)

The flowers are edible and excellent bee forage. It's a minor honey tree in Cuba. Skip the seeds. They are reported to be poisonous, and the roots, stems, and leaves carry hydrocyanic acid.

Pests and diseases

Few serious insect problems. In humid climates the usual suspects:

• Aphids, with sooty mold following on the honeydew
• Leaf spots: Cercospora, Gloeosporium, Phyllosticta; algal leaf spot (Cephaleuros); anthracnose
• Root rots (Fusarium, mushroom root rot) on badly drained sites

Container-grown plants are generally cleaner, with fewer leaf-spot and sooty-mold problems than in the humid tropics.

Cultivars and selections

Tree habit. Dense crown of slender, wide-spreading branches. Hana Hwy, Maui. Forest & Kim Starr, CC BY 3.0, via Wikimedia Commons

There are no registered cultivars to chase. Breeders have basically ignored this species. Almost everything is seedling-grown, and polyembryony means seedlings come reasonably close to the parent. Visible variation is mostly fruit color (pale yellow vs. pink-blushed) and timing. Some Indian selections fruit in February to March instead of the usual June to July crop. India has worked on vegetative propagation specifically to fix dwarf types.

Find a tree you like, with better flavor, bigger fruit, or earlier season, and air-layer it. The next seed may not match.

Growing record

Date	Location / climate	Plant age	Height	Flowering	Fruiting	Notes

Sources

• Morton, J. 1987. Rose Apple, Fruits of Warm Climates (Purdue NewCROP). Seasons, propagation, pests, uses, toxicity.
• Useful Tropical Plants: Syzygium jambos. Climate tolerances, polyembryony, germination, frost tolerance.
• Growables: Syzygium jambos. USDA zones 9 to 11, common names in 20+ languages, relatives.
• Top Tropicals: Rose Apple. Container fruiting, care, cold tolerance to 20s °F.
• Plants For A Future: Syzygium jambos. USDA hardiness 9 to 12, known hazards.
• San Marcos Growers: Syzygium jambos. Hardy to 25 °F, frost and fruiting note.

Image credits

• Whole fruit: PMATAS, CC BY-SA 4.0
• Flowers: Ajtjohnsingh, CC BY-SA 4.0
• Young leaves: Tonton Bernardo, CC BY-SA 3.0
• Fruit and seeds: JonRichfield, CC BY-SA 3.0
• Tree habit: Forest & Kim Starr, CC BY 3.0