The cardinal vine (Ipomoea x multifida) has flowers in an especially strong, true red, with deeply colored, blue-green foliage. A hybrid developed for profuse blooming, it's also a strong climber that grows as an annual in almost all climates. This versatile vine makes a statement wherever you plant it, and attracts hummingbirds.
The red cardinal vine is a fast-growing, twining plant that can reach a height of 10 to 20 feet when given the right growing conditions. It has deeply cut, ferny leaves that make an attractive display, even when the plant's not in flower. Its blossoms are deep red, tubular and about 1 inch across, and highly attractive to hummingbirds. The flowers begin opening in early summer and can continue into early winter in warm regions. Cardinal vine is a good choice to plant near a mailbox post, trellis, fence or other support, which it climbs quickly and covers in foliage and profuse spots of deep red color. It usually climbs without any help, but might need some guidance when young to reach and twine about its support.
Cardinal vine also does well grown in a container, provided the plant is kept in full sun, which it needs for best growth and flowering. Planted in a hanging pot or basket, the vines cascade attractively over the edge of the pot. Because the vine grows quickly, you may need to twine the vines upward through the pot's hanger several times to keep them from reaching the ground. You can also grow red cardinal vine in a pot that contains a trellis or hoop support, twining it through the support as it grows.
Red cardinal vine also makes a dense ground cover when allowed to trail along the ground. Its flowers turn toward the light source, so its red blossoms face upward and outward as it grows, making a dramatic display. You can inter-plant red cardinal vine with short annuals or perennials in a mixed bed or border, or allow it to trail across the ground and fill in an open area. The plant can also grow along the ground under a tree, provided the tree's canopy is high enough to allow strong sun to reach the vine.
In addition to needing full sun for best growth, cardinal vine does well in any fertile, well-draining garden soil. Adding compost at planting can increase your soil's organic content and fertility. If your soil contains clay and drains slowly, mix in some fine sand at planting to improve its drainage. You can sow seeds directly into the garden in spring, or start seedlings indoors in peat pots two or three weeks before the last spring frost. Soaking seeds in water for 24 hours before planting helps improve germination. Although foliage and flowers of this plant are not toxic, its seeds are highly toxic and should never be eaten.