Photo: Eric Hunt, CC BY-SA 4.0 · source
Pruning guide · Perennial
Great blue lobelia: when and how to prune
Lobelia siphilitica
Great blue lobelia is best pruned in March.
| Pruning months | March |
|---|---|
| Flowering | August–October |
| Good for bees, butterflies and birds | Yes, for bees |
| Native to Belgium | No, planted |
| Poisonous to people and pets | Yes, take care with children and pets |
Great blue lobelia: when to prune it?
In March cut away the old stems; in autumn only if you want a tidy border.
What else to prune in those months? March
Great blue lobelia: how to prune it?
- In March, cut the old stems down to just above the ground, without damaging the new rosettes.
- Leave the stems standing in autumn if you want the plant to self-seed; they also give the border winter structure.
- Cut faded spikes back to just above a side shoot if you do not want seedlings.
How much to cut, and how often?
- One pruning period a year: March.
What does it mean for wildlife?
- Great blue lobelia flowers in August–October, when it attracts bees.
- If you only cut back in March, the old stems stand through the winter: insects overwinter in them and birds eat the seeds.
Caution: Wear gloves: the milky sap is poisonous and can irritate the skin.
Nearby: related pruning guides
Plant profile: Great blue lobelia · Pruning calendar and basic rules
This guide is compiled from the Bladwijzer plant profile and pruning calendar.