Botanical Name: Lobelia erinus ‘Hot® Purple’

Common Name: Annual Lobelia

Hardiness Zone: Grown as an Annual in All Climates

Size: 6–10" Tall × 10–14" Spread

Growth Habit: Compact, Mounding to Lightly Trailing Habit

Sunlight: Full Sun to Partial Shade (Best Performance in Morning Sun / Afternoon Shade)

Soil: Well-Drained, Moisture-Retentive Soil

Water Needs: Moderate; Prefers Consistent Moisture

Bloom Season: Spring through Fall (Excellent Heat Tolerance for Lobelia)

Fertilizer: Light, Regular Feeding for Best Performance

Features: Rich Purple Blooms with White Eyes, Improved Heat Tolerance, Dense Flower Coverage

Uses: Containers, Hanging Baskets, Window Boxes, Borders, Cool-Season Color

Patent: ✔ Patented

Propagation: ❌ Propagation Prohibited Without License

See our complete Lobelia Plant Guide for more in depth care details.

More About Lobelia ‘Hot® Purple’

‘Hot® Purple’ produces rich purple blooms accented by crisp white eyes, creating a bold color contrast that stands out against other Lobelias. The flowers are small but numerous, forming a dense layer of color that covers the plant and keeps it looking fresh and vibrant through the season. The deep purple tones give the plant a bit more visual weight than many lighter blue lobelias, which makes it particularly effective in container combinations where strong color contrast helps the planting read clearly from a distance.

The plant forms a compact, well branched mound that naturally fills containers without becoming leggy. The growth habit stays dense through the center, while the outer stems gently spill over the edges of containers, window boxes, and hanging baskets. This slight trailing effect softens container edges and gives plantings a fuller, more finished appearance without becoming overly aggressive. Because of its balanced growth habit, ‘Hot® Purple’ works equally well in upright containers or cascading arrangements. It blends easily with other cool season annuals while still holding its own visually.

Why We Like It (Our Trials)

In our trials here in the Upstate, ‘Hot® Purple’ has proven to be one of the most dependable heat tolerant lobelias we grow. While many lobelias begin to fade as temperatures warm, this variety continues pushing fresh blooms while maintaining strong color and good plant density. With consistent moisture and decent airflow, it holds its shape and vigor remarkably well for a cool season flowering plant.

We also appreciate how consistently it fills containers without requiring much intervention. The branching habit creates a naturally full plant, reducing the need for trimming or pinching to keep it looking balanced. Even in mixed containers with faster growing companions, it tends to hold its space nicely without disappearing. One of my favorite things about ‘Hot® Purple’ is how easily it intensifies color combinations. The saturated purple works beautifully with whites, yellows, pinks, and chartreuse foliage, helping other plants pop while still contributing strong color on its own.

Hot® Purple vs. Other Lobelia Varieties

Hot® Purple is grown first and foremost for its bold, saturated color, bringing a warmer, more energetic tone than traditional blue Lobelias. Unlike Cardinal Flower, which is chosen for height and permanence, Hot® Purple is a compact annual used for early-season containers and cool-weather color. Its rich purple blooms immediately stand out in mixed plantings, especially when paired with lighter companions. This variety is often selected when color impact is more important than refined structure.

Compared to softer trailing options like Rift Purple, Hot® Purple reads stronger and more assertive. It lacks the tight uniformity of the Techno® Dark Blue, and the disciplined form of Magadi™ Compact Blue Bay, but it compensates with visual punch. From a gardener’s perspective, Hot® Purple is the choice when you want Lobelia to be noticed rather than blended, making it ideal for high-contrast spring containers.