Cardinal flower vs Great blue lobelia
Two native lobelias of wet ground, often planted together. Cardinal flower has spikes of the purest scarlet, pollinated almost entirely by hummingbirds; it needs soil that stays wet, and each plant lives only a few years. Great blue lobelia is its blue cousin, flowering a little later, sturdier and longer-lived, and happy in ordinary moist garden soil. The two cross, and purple seedlings sometimes appear where both grow.
 Cardinal flowerLobelia cardinalis |  Great blue lobeliaLobelia siphilitica | |
|---|---|---|
| Size | 3½ ft tall, 16 in wide | 2½ ft tall, 16 in wide |
| Plant | 14 in apart | 14 in apart |
| Zones | 3 to 9 | 4 to 9 |
| Light | Full sun to part shade | Full sun to part shade |
| Soil | Moist to wet, rich fertility | Evenly moist, rich fertility |
| Flowers | Late July to mid September; red | Early August to mid September; blue |
| Leaves | Medium, herbaceous | Medium, herbaceous |
| Job in a bed | Accent | Accent |
| Pets | Toxic (moderate) | Toxic (mild) |
| Deer | Not listed as resistant | Resistant |
| Native | Yes | Yes |
| Spread | Low risk | Moderate risk |
Rows where they differ are marked. Flowering times are for zone 5.
Which to choose
- Choose cardinal flower for colder gardens (to zone 3).
- Choose great blue lobelia for deer country.
Can they grow together?
Yes: they are recorded as partners. What great blue lobelia brings beside cardinal flower: in flower together for six weeks, from early August. They share full sun, part sun and part shade and zones 4 to 9.
Read more: all about cardinal flower, and all about great blue lobelia, each with a bed the planner designed around it.