Cardinal climber (Ipomoea × sloteri)

Overview

The Cardinal climber, scientifically known as Ipomoea × sloteri, is a vigorous annual twining vine celebrated for its spectacular display of bright red, tubular flowers that last from mid-summer right up to the first hard frost. This hybrid plant results from the cross between the Cypress Vine (I. quamoclit) and the Scarlet Morning Glory (I. coccinea), combining desirable traits from both parents. Gardeners prize this specimen for its speed of growth, its ability to rapidly cover structures, and its exceptional appeal to hummingbirds.

Characterized by finely textured, deeply dissected foliage, Ipomoea × sloteri typically reaches heights between 10 and 15 feet, making it an excellent choice for vertical gardening. While it thrives in full sun, it maintains a relatively low maintenance profile once established, requiring only medium water and standard soil preparation.

As a cultivated hybrid, the value of the Cardinal climber lies firmly in its ornamental display and its ability to quickly inhabit trellises or fences. Its dazzling red blooms provide a vibrant vertical accent in summer landscapes, offering necessary structure and color where space optimization is necessary.

Fast Facts

• Plant Family: Convolvulaceae
• Plant Type: Vine
• Native Range: Cultivated origin
• Hardiness Zones: USDA Zones 3-11
• Size at Maturity:
  • Height: 10-15 ft
  • Spread: 0.5-1 ft
• Bloom Time: July to frost
• Bloom Description: Red
• Sun Exposure: Full sun
• Water Needs: Medium
• Maintenance Level: Low

How to Grow

To successfully cultivate the Cardinal climber, start seeds indoors about four to six weeks prior to the average last frost date, especially if you have a shorter growing season. Because the seed germination can be slow, it is beneficial to scarify the seeds (lightly nicking the hard coating) and soaking them in water for several hours before planting. Plant outdoors only once all danger of frost has completely passed and the soil has begun to warm up.

The optimal environment for Ipomoea × sloteri includes rich, well-draining soil that remains consistently moist. While the plant is somewhat tolerant of light shade, maximum floral performance requires full sun exposure. Fertilization is usually unnecessary if the soil is rich, as too much nitrogen can encourage excessive foliage growth at the expense of blooms.

Watering should be consistent, falling into the ‘medium’ requirement category—avoid letting the soil dry out completely, particularly during peak bloom periods. This annual vine requires vertical support such as a trellis, arbor, or sturdy netting to climb successfully. In warmer climates, be aware that the Cardinal climber can readily self-seed; monitor young sprouts in spring if you wish to control its spread.

Landscape Uses

The inherent climbing nature of the Cardinal climber makes it an ideal candidate for vertical gardening solutions where height and density are desired. It excels when grown on structures like trellises flanking an entryway, overhead an arbor to create a temporary shaded walkway, or softening the look of an unsightly utility pole. Use this vine as a dynamic vertical accent within sunny mixed borders, allowing it to climb stakes interspersed among shorter perennials.

For smaller spaces or patio settings, Ipomoea × sloteri can be successfully grown in large containers, provided it is given a secure, built-in support structure from the start. When choosing companions, select plants that share its preference for full sun and medium moisture levels, such as zinnias, cosmos, or marigolds, which will complement the vine’s intense red color during the summer months.

Standout Features

Flower Qualities

• Showy

Noteworthy Characteristics

Ipomoea × sloteri, commonly called cardinal climber, is an annual twining vine that resulted from the deliberate, interspecific hybridization of two Ipomoea species: I. Quamoclit (cypress vine) and I. Coccinea (scarlet morning glory). Mature vines can reach up to 15’ tall and around 1’ wide. The deeply dissected, finely textured foliage can reach up to 3” long and 2” wide. The bright red, outward-facing, 2” long tubular flowers are held singly or in loose clusters of 2-5 blooms. The flowers are highly attractive to hummingbirds. This plant is a tetraploid hybrid, meaning that a full set of chromosomes from each of the parent species is present in the hybrid. It can be distinguished from the very similar I. × multifida by its larger flowers and wider, more numerous leaf lobes. Synonymous with I. Sloteri.

Tolerances

No specific tolerances were listed.

Potential Problems

Fortunately, the Cardinal climber rarely faces significant pest issues or major debilitating diseases, making its maintenance level quite low. The primary concern for gardeners in regions with long, warm growing seasons is its propensity to reseed readily. If you do not wish for the Ipomoea × sloteri seedlings to populate your garden beds uncontrollably the following year, ensure you remove spent flowers or allow the seeds to mature only in designated areas.

If seedlings do appear unexpectedly, they are easily managed while small. Cultivate the soil lightly around the base of any unwanted seedlings to disturb their roots, or simply pull them out manually before they establish a deep taproot.

Frequently Asked Questions

What hardiness zones is Cardinal climber suitable for?

The Cardinal climber (Ipomoea × sloteri) is quite versatile, thriving in USDA Zones 3 through 11 when grown as an annual.

How large does Ipomoea × sloteri grow?

This vine typically matures to heights between 10 and 15 feet tall, possessing a relatively narrow spread of only 0.5 to 1 foot wide.

Sun exposure does Cardinal climber need?

For the most spectacular floral display, plant Ipomoea × sloteri where it receives full sun exposure throughout the day.

Conclusion

The exceptional hummingbirds attraction and vibrant red, late-season blooms make the Cardinal climber a rewarding choice for vertical interest in any landscape. By ensuring adequate structure and consistent moisture, this low-maintenance annual, Ipomoea × sloteri, will provide continuous color through the hottest months. Check your local last frost date and plan to start your seeds indoors for the earliest possible performance this season.

Wildlife Benefits

The rich, tubular red flowers of the Cardinal climber are perfectly shaped to accommodate the long bills of hummingbirds. These nectar-rich blooms provide a crucial late-season food source that helps migrating birds refuel, making this vine an invaluable addition to any wildlife-friendly garden design. You will observe consistent visits throughout the day once the blooming period kicks off in July.

Propagation Tips

Since Ipomoea × sloteri is an annual hybrid, propagation is almost exclusively done via seed. As noted in the culture section, these seeds benefit significantly from pre-treatment to ensure successful germination. Always scarify the seed coat, perhaps by scratching lightly with sandpaper or a knife point, followed by a soaking period of several hours. This preparation mimics natural weathering processes and speeds up the emergence of the seedling, which can otherwise be frustratingly slow. Direct sowing is feasible in warming soil after all frost danger has passed in long-season climates.