💙 Lobelia
Lobelia erinus
Electric-blue edging that flowers so hard it practically vibrates.
Sun
Full sun to part shade (afternoon shade in heat)
Days to harvest
Annual; blooms spring through fall
Spacing
6-8 inches apart
Soil pH
6.0-7.0
How to grow
Start seeds indoors 10-12 weeks before last frost — the dust-like seeds need light and patience. Lobelia is a cool-season lover that pumps out unreal blue flowers in spring, then melts in real heat; in Florida, plant in fall for winter-spring color. Shear back midseason when it gets leggy for a fresh flush.
Water & feeding
Keep consistently moist — it wilts fast and doesn't forgive drought the way tougher annuals do.
Common problems
- Heat shutdown — the main issue; plan for it, don't fight it.
- Aphids and spider mites in stress.
- Leggy in too much shade.
Harvest
Shear spent plants back by half midseason instead of deadheading individual tiny flowers — power tools beat tweezers here.
Nerdy fact: True blue is one of the rarest colors in flowers — most 'blue' blooms are actually purple. Lobelia's intense blue comes from delphinidin pigments at just the right cell pH. It's botanical structural color, basically.