The cardinal plant (Lobelia cardinalis) is a native flowering plant to the eastern United States and regions in Canada. Its intensely red, 1½- to 2-inch tubular-shaped flowers form on long stalks beginning in the middle of July, and continue through October. Cardinal plants prefer partial shade, with moist, bog-like growing conditions. It's hardy in zones 3 through 10.
How to Plant Cardinal Plant Seeds
Place 1 1/2 to 2 cups of potting soil into a plastic resealable bag. Place into the bag approximately ¼ to ½ cup of warm water. Add the cardinal plant seeds to the bag, shake it gently. Seal the bag and place it into your refrigerator for two months.
Check on the plastic bag weekly. Keep the soil in the bag consistently moist. Spritz the soil in the bag with water when necessary. Remove the bag after two months. Plant the seeds into a seed-starting tray.
Fill up a seed-starting tray with sterilized seed-starting mix. Place the tray into the irrigation tray. Add enough water so the soil becomes damp.
Scatter the cardinal plant seeds randomly on the surface of the soil in the tray. Push the cardinal plant seeds into the soil. Avoid covering them with any soil.
Place the entire tray in a warm, light-filled area (provide six to eight hours of light a day). Keep the temperature between 65 and 75 degrees Fahrenheit. Germination of cardinal plant seeds can take up to two to three weeks. Keep the cardinal plant seedlings moist; do not allow them to dry out. Once the seedlings have reached about 1 inch tall, transplant them into individual pots.
Transplanting Cardinal Plant Seedlings
Fill up each pot with potting mix. Make sure the soil is firmed down, but not packed hard.
Remove cardinal plant seedlings in small clumps, so as not to disturb the roots any more than necessary. This is based on a U.S. Department of Agriculture recommendation. With a spoon, make a hole, 2 inches wide and deep, in the center of each pot.
Scoop out a small clump of seedlings from the tray. Carefully place the clump of seedlings into the pot. Add or remove soil so that the roots of the seedling are sitting firmly upon the base of the soil. Carefully scoop in soil around the seedling until the hole is filled up. Firm down the soil around the base of the seedling with your spoon.
Place the pots into the irrigation tray. Add water until you see the soil in the pots become damp. Once no more frost is expected in your growing region, plant your seedlings outside. According to the USDA, cardinal plant seedlings are ready to plant outdoors 12 to 16 weeks after planting.