Lobelia (often called Edging Lobelia) is a total showstopper. Those vibrant blue and purple blooms make it a favorite for adding a pop of color to balconies and flower beds alike. If you’re looking to add this beauty to your garden, here’s everything you need to know to get it right.
Timing is Everything
Originally hailing from South Africa, Lobelia is a fan of warmer weather. It’s generally not hardy enough to survive a frost, so you’ll want to wait until the danger of the last spring frost has passed before planting. In most areas, May is the sweet spot to start. If you’re working with young starts, it pays to be patient and wait for consistently warm days. You can move potted plants outside during the day to harden them off, but make sure to bring them back in if the nights are still chilly.
Finding the Perfect Spot
Whether you’re planting in the ground or in containers, Lobelia craves sunshine. While it can survive in partial shade, you won’t get that lush “carpet of flowers” look without plenty of light. Try to pick a spot that’s also protected from harsh winds. If you’re planting in a garden bed, Lobelia is a bit picky about its soil—it loves loose, nutrient-rich, sandy-loam soil. Good drainage is key to preventing root rot. If you’re using pots, adding some gravel or broken terracotta pieces at the bottom can help keep the water flowing.
Tips for Starting from Seed
To get a head start on those gorgeous blooms, it’s a smart move to start your seeds indoors. You can find seeds online or at your local nursery. Small seed trays are perfect for this. Just fill them with a good seed-starting mix and gently press the seeds into the surface. Don’t bury them! Lobelia seeds need light to germinate. Keep the soil consistently moist but not soggy.
The ideal temperature for germination is between 60°F and 65°F (16-18°C), and they love a bit of humidity. Once May rolls around, your seedlings will be ready to move to their permanent home. Many gardeners prefer starting fresh each year this way, as overwintering a perennial variety can be a bit of a project.
Planting Blue Lobelia: The Cheat Sheet
- Best time: After the last frost in May
- Be extra patient with young seedlings
- Great for both garden beds and containers
- Location: Bright and sunny
- Soil: Nutrient-rich, loose, and sandy-loam
- Avoid standing water (good drainage is a must!)
- Start seeds indoors in trays
- Don’t cover seeds with soil; they need light
- Ideal temp: 60°F to 65°F
- Keep humidity high during germination