Croton and Mandevilla Hardiness: Not for Zone 8b Outdoors

Cold Tolerance

• Croton (Codiaeum variegatum): Zone 10 (no frost).
• Mandevilla: Most Zone 9 (–5°C / 23°F). A few cultivars slightly hardier, but risky in 8b.

Verdict

In Pacific Northwest zone 8b, both will die in a typical winter. Keep them as container plants to move indoors, or enjoy as summer annuals.

Alternative

Bougainvillea (which you noted grows year-round) is a better permanent landscape choice for your zone.