Hey everyone,
Big thanks for sharing your cultivation experience.
I’m starting an outdoor cultivation project growing rare Australian acacias in the Sierra Nevada foothills of California, approximately 60 miles southeast of Sacramento. I want to give complete climate and soil data so any responses are grounded in real conditions rather than native range assumptions.
Location data:
• Elevation: 1,200 ft (366m)
• USDA Zone: 9a
• Soil: Decomposed granite and granitic loam, fast-draining, low organic matter, slightly acidic pH 5.5–6.5. Rocky outcroppings on slopes. Water moves through rapidly even in the wettest months.
• Annual rainfall: 28–33 inches (710–840mm)
• Rainfall pattern: Classic Mediterranean Csa — approximately 95% falls October through April. July and August receive essentially zero precipitation. Bone dry June through September.
Monthly temperature data:
|Month |Avg High |Avg Low |
|---------|-----------|-----------|
|January |55°F / 13°C|39°F / 4°C |
|February |57°F / 14°C|39°F / 4°C |
|March |60°F / 15°C|41°F / 5°C |
|April |66°F / 19°C|43°F / 6°C |
|May |74°F / 23°C|48°F / 9°C |
|June |83°F / 28°C|55°F / 13°C|
|July |91°F / 33°C|59°F / 15°C|
|August |90°F / 32°C|59°F / 15°C|
|September|85°F / 29°C|57°F / 14°C|
|October |73°F / 23°C|51°F / 11°C|
|November |62°F / 17°C|44°F / 7°C |
|December |53°F / 12°C|38°F / 3°C |
Cold floor — the honest numbers:
Average winter lows sit around 38–40°F (3–4°C) and the area rarely drops below freezing — avocado trees are growing and surviving in the town area, which gives a practical indication of the real cold exposure. On radiation frost nights during severe Arctic outflow events, the absolute worst-case temperature on a south-facing slope with good cold air drainage at this location is approximately -7°C (19°F). Events of this severity are rare — roughly once per generation — with the last major event in the region being December 1990. Typical frost nights run -1 to -3°C, approximately 25–40 nights per year, November through February.
Humidity: Low — relative humidity drops to 20–30% in July and August. Winter humidity 60–80% during rain events.
Irrigation: Available year-round from a reliable water source. Drip irrigation planned through the dry season.
Planting site: South-facing granitic slope, not a valley floor. Maximum solar exposure, skeletal fast-draining soil, excellent cold air drainage.
My questions:
1. Acacia acuminata (narrow phyllode variant specifically)
Has anyone grown narrow phyllode acuminata outdoors with 28 inches or more of annual rainfall and had it genuinely establish and thrive — not just survive? My primary concern with this rainfall level is not cold but root rot during the wet winter months — the granitic slope site should provide good drainage but I’d welcome any experience growers have had with fungal root issues in higher rainfall climates and how they managed them. Acacian — how are your acuminatas doing? Are they thriving? What is the lowest temperature they have actually faced and survived? Any other growers with outdoor acuminata in comparable or wetter climates, please share your data — lowest temperatures survived, annual rainfall, and how long the plants have been in the ground.
2. Acacia courtii
My understanding is that courtii is more cold sensitive than acuminata — potentially damaged below around -4°C and at serious risk below -6 or -7°C. Given that my slope site has a realistic worst-case cold floor of around -7°C, courtii sits right at the margin. Is there any grower experience that would clarify whether it could survive a typical winter at this site, even if a severe once-per-generation event might kill it?
3. Acacia phlebophylla
I understand phlebophylla is native to the cool wet alpine environment of Mt Buffalo in Victoria, where summers are moist and mild — the opposite of what I’m offering. My summers are hot and bone dry, with July highs averaging 91°F (33°C) and essentially zero rainfall from June through September. My winters are mild by alpine standards — worst-case -7°C on the slope, with typical frosts only reaching -1 to -3°C.
The question I’d genuinely like this community’s opinion on: does the hot dry Mediterranean summer represent a fundamental barrier for phlebophylla? And does the relatively mild winter — much milder than Mt Buffalo — actually work in its favour compared to the harsher alpine cold it evolved with? Has anyone attempted phlebophylla in any climate with hot dry summers?
Thanks in advance!