The best time to plant gladiolus bulbs is in spring. Specifically, you should plant them:
- In pots from March (kept in a frost-free place such as a greenhouse) or directly into the ground from May.
- Roughly two weeks before the last expected spring frost.
- Stagger planting every 1-2 weeks until early July to extend blooming through the summer.
- The latest planting time is July; planting later may result in no flowers before frost arrives.
Plant the bulbs about 4-6 inches deep (10-15 cm) in well-drained soil with full sun exposure. On heavier soils, adding horticultural grit can improve drainage. Space bulbs 3 to 6 inches apart. This timing and planting depth will help ensure a healthy bloom period in summer.