Although its flowers may be tiny, trailing lobelia can hold its own in a hanging container. It can occupy a pot on its own, or its bold shades of lavender, purple and blue can provide contrast when it is planted alongside larger plants with bigger blossoms. The little showoffs may be low-maintenance, but they're generous bloomers that will provide a mass of color that lasts all summer. Start trailing lobelia seeds indoors in mid-February and by spring they'll be ready to plant outside.
Fill the divided planting tray or 2-inch pots with commercial potting soil. Moisten the soil lightly with water from a mister.
Sprinkle a few seeds on the surface of the soil. Trailing lobelia seeds are tiny and shouldn’t be covered with soil, which will prevent light from reaching them.
Cover the trays or pots with a piece of clear plastic, then put them under a grow light. Windowsills, which are usually too cool at night and too warm during the day, aren’t good places to germinate seeds.
Remove the plastic when the soil appears dry. Mist it lightly with water, then replace the plastic. The soil should be kept damp at all times, but never soaked.
Pull off the plastic when the seedlings emerge, but keep the trays under the grow lights.
Plant trailing lobelia outdoors when the weather turns warm and all danger of frost has passed, but harden them off for two weeks first. Put them outdoors in the shade for a few hours each day and bring them in at night. Gradually move the seedlings into the sunshine as you increase the amount of outdoor time.
Fill a hanging container with potting soil and mix in a handful of compost or well-rotted manure. Plant the trailing lobelia and water it thoroughly.
Put the hanging container in a sunny location, or in partial shade if you live in a sunny, hot climate. If possible, keep the container out of the wind. Lobelia doesn’t do well in windy conditions, which will cause the tips of the plants to turn brown.