Macarthur palm overview
The clustering Macarthur palm of tropical streets and atriums. USDA 10a to 12. Kew's accepted name is Ptychosperma propinquum. Nurseries still use macarthurii.
Region of origin
New Guinea to northern Australia
Native countries
Historical discovery
Gardens have sold it as Ptychosperma macarthurii for more than a century. Kew now accepts Ptychosperma propinquum. Clustering slender trunks and red fruit are the look.
Names
Common names
Macarthur palm, MacArthur palm, Horseshoe palm
Synonyms
- Ptychosperma macarthurii (H.Wendl. ex H.J.Veitch) H.Wendl. ex Hook.f.
Cold hardiness
Survives about 28°F / -2°C. Outdoor range USDA 10a–12a. Hover or click a zone, state, or country. Switch the U.S. map between states and hardiness zones.
Highlighted USDA zones 10a–12a. Green countries can be grown outdoors.
United States
In range Too cold
World
Native Can be grown
Alaska and Hawaii are state outlines with their overall zone range. A country is painted if its mildest inhabited winter is at least one USDA step milder than this palm’s hardiness.
Scientific facts
- Clustering, slender, with a small crownshaft and jagged leaflet tips.
- Kew lumps the old macarthurii name under P. propinquum. Some nursery stock is other Ptychosperma.
- Frost-free. Not a zone 9 street tree.
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Full care guide
The Macarthur palm is a clustering Ptychosperma sold for tropical streets and bright atriums. USDA 10a to 12. Kew's accepted name is Ptychosperma propinquum. Labels still say P. macarthurii. It wants heat and water, not a freeze.
Common Names:
Macarthur palm, MacArthur palm, horseshoe palm.
Scientific Name:
Ptychosperma propinquum (Becc.) Becc. ex Martelli. The garden name Ptychosperma macarthurii is a synonym.
Origin:
New Guinea to northern Australia.
Appearance:
Several slender, ringed trunks, a short green crownshaft, and pinnate leaflets with jagged tips. Red fruit. It is a clump, not a solitary royal.
Growth Rate:
Moderate to fast in heat.
Max Growth Height:
Often 20 to 30 feet.
Foliage Spread:
A clump 10 to 15 feet wide.
Cold Hardiness and Hardiness Zone:
USDA 10a to 12. Damage around 28°F (-2°C). Zone 9b is a sheltered gamble.
Soil Type:
Rich, moist, well-drained. Sand needs irrigation.
Fruit and Flowering:
Orange to red. Messy on walks. Birds like them.
Can it Grow Indoors:
A young clump in a bright atrium, not a long-term desk plant.
Light Requirements:
Full sun to light shade in the humid tropics. Young plants like a little protection from dry inland sun.
Water Requirements:
Even moisture.
Maintenance Level:
Medium. Thin crowded canes if you want. Feed in the growing season with palm-specific fertilizer. Fruit drop is the mess.
Common Diseases/Pests:
Scale, mites in dry wind, and nutrient yellowing in sand.
Plant Care:
Heat, water, frost-free. If your winter still freezes, this is the wrong clustering palm. Try lady palm or European fan instead.
Macarthur palm Frequently Asked Questions:
1. Why does Kew say propinquum?
Palms of New Guinea (2024) treats macarthurii as a synonym of Ptychosperma propinquum. Shops have not caught up.
2. Macarthur or solitaire palm?
Solitaire is Ptychosperma elegans, usually a single trunk. Macarthur is the clustering one.
3. Can I grow it in zone 9?
Not as a reliable outdoor clump. Keep it for 10a and warmer, or a greenhouse.
4. Good indoor palm?
A young plant in a bright, humid space. It wants to be a courtyard clump.
Plant Macarthur palm in genuine tropical heat as a clustering street or atrium palm. If the tag is the only reason you wanted it in zone 9, pick a hardy clump instead.