Knowing how to grow and care for lobelia can add a touch of beauty to your garden. Lobelia (Lobelia cardinalis) is perennial, flowering plant native to most of North America. The herb has striking, red flowers that bloom in mid to late summer and in the early fall. Lobelia has been deemed poisonous, however; do not ingest any part of this plant.
Hummingbirds and butterflies love lobelia and it is a beautiful addition to your garden. Lobelia is easy to grow and hardy in zones two through nine. Plant seeds indoors in small containers or egg cartons filled with rich, fertile soil several weeks before the last frost. Once the threat of frost has passed and your young seedlings are several inches high, you can move them outdoors. You'll space the plants 15 to 18 inches apart in rich soil with a pH of 6.1 to 7.8. Unlike other herbs in your garden, lobelia enjoys wet soil. When found growing voluntarily, lobelia flourishes next to streams and creeks. Water this plant well and on a regular basis. Keep the soil moist and do not let it dry out between waterings.
Your mature lobelia plants will reach heights of 24 to 36 inches. They enjoy full sun but also tolerate and thrive in partial shade. If you plant seeds directly in your garden, get the seeds into the soil in late fall and mulch well. This allows the seeds to germinate over the winter, and you should have healthy plants sprouting by the following spring. If you're planting in the spring, sow seeds directly in the ground after soil temperatures have reached 70 degrees. Within four weeks of consistent, warm soil temperature, the seedlings will sprout. Weed regularly around lobelia and don't allow other plants to invade.