Botanical Name: Lobelia erinus ‘Rift Blue’

Common Name: Annual Lobelia

Hardiness Zone: Grown as an Annual in All Climates

Size: 6–10" Tall × 12–18" Spread

Growth Habit: 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 Early Summer (May Persist Longer in Mild Weather)

Fertilizer: Light, Regular Feeding for Best Flowering

Features: Intense Deep Blue Blooms, Excellent Color Saturation, Dense Flower Coverage

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

Patent: ❌ Not Patented

Propagation: ✔ Propagation Allowed

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

More About Lobelia ‘Rift Blue’

Lobelia ‘Rift Blue’ is valued for its exceptionally deep, saturated blue flowers, offering one of the richest blue tones you will find among annual lobelias. The blooms appear in dense clusters that quickly cover the foliage, creating a vivid carpet of color that immediately stands out in containers and mixed plantings. When the plant reaches peak bloom, the flowers layer tightly together, producing a strong block of color that feels bold despite the plant’s compact size. 

The intensity of the blue is what really separates this variety from many other Lobelias. While some types lean toward lighter sky blues, ‘Rift Blue’ carries a richer, more saturated tone that reads clearly from across the garden. This deeper color gives it a bit more presence in mixed plantings and helps it anchor container combinations where softer blues might fade into the background. It works well in upright containers where the mounded center adds fullness, and it also performs nicely in hanging baskets and window boxes where the trailing stems can cascade slightly over the sides.

Why We Like It (Our Trials)

In our trials here in the Upstate of South Carolina, ‘Rift Blue’ has performed especially well in early Spring plantings and during cooler weather. It establishes quickly and begins producing flowers early, often building a strong bloom display before many other annuals really get going. That early color makes it a valuable plant for refreshing containers and seasonal displays at the start of the gardening season. With consistent moisture and good airflow, the plants remain compact and floriferous without thinning or stretching. 

I remember the first season we trialed ‘Rift Blue’ here at the garden center. Early in the Spring it looked great, which most lobelias do, but what caught my attention was what happened a few weeks later. As temperatures started creeping up, a lot of the older Lobelia varieties nearby began to thin out and lose their punch. ‘Rift Blue’, on the other hand, just kept going. What really sold me on this variety, though, was the depth of the blue. That deeper tone gives it a stronger presence in mixed containers, especially when you start pairing it with other colors.

Rift Blue vs. Other Lobelia Varieties

Rift Blue is selected for its graceful trailing habit, making it one of the strongest spiller options among annual Lobelias. While Magadi™ Compact Blue Bay and the Techno® series focus on structure, Rift Blue emphasizes movement, flowing naturally over container edges and window boxes. Its cool blue tone is classic and easy to pair with whites, yellows, and silver foliage.

Compared to Rift Purple, Rift Blue feels cleaner and more traditional in color, while Rift Purple adds warmth and depth. Against Hot® Purple, Rift Blue is far more restrained and easier to integrate into complex designs. From a gardener’s standpoint, Rift Blue is the go-to choice when softness and cascade are the priority.