Cambridge Blue Lobelia Seeds 77 to 84 days to maturity. Lobelia erinus. Annual. Open Pollinated. Cambridge Blue lobelia is brilliant, easy to grow from seed, and perfectly suited for many humid and temperate climates. Cambridge Blue seeds will excite your home, patio, and garden with fast-growing 4-6" tall lobelia with ½" tubular powder blue blooms. About 520,000 seeds per ounce.